US Patent # 5,416,391
US Cl. 318/558; 307/106; 313/581 ~ 16 May 1995
Electromechanical Transduction of
Plasma Pulses
Paulo N. Correa & Alexandra N. Correa
Abstract ~ A direct current power
transducer for driving alternating current devices utilizes
a discharge tube connected across a current source, the
construction of the tube and characteristics of the source
being such as to maintain endogenous pulsed abnormal gas
discharge within the tube. The tube is capacitatively
coupled to an external load including an alternating current
device, typically an electric motor. Electric motors of the
asynchronous induction or synchronous types are particularly
suitable, but other alternating current devices may be used.
By adjustments to the current source, the capacitance in
parallel with the discharge tube, and connections to
auxiliary electrodes, the pulse repetition frequency of the
discharge may be adjusted, thus allowing variable speed
control of types of alternating current motor not normally
amenable to such control.
References Cited ~
US Patent Documents:
3,205,162 ~ Sep., 1965 ~ MacLean.
3,471,316 ~ Oct., 1969 ~ Manuel.
3,628,164 ~ Dec., 1971 ~ Tikhomirov.
3,663,855 ~ May., 1972 ~ Boettcher.
3,678,510 ~ Jul., 1972 ~ Walthard et al.
4,063,130 ~ Dec., 1977 ~ Hunter, Jr.
4,194,239 ~ Mar., 1980 ~ Jayaram et al.
Primary Examiner: Ro; Bentsu ~ Attorney, Agent
or Firm: Ridout & Maybee
Description ~
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a high power gas
discharge tube of novel characteristics, and to applications
of the tube in the control of electric motors and other
alternating current devices.
2. Review of the Art
As the current passed through a gas discharge
tube is increased beyond the levels at which normal glow
discharge takes place, such normal gas discharge being
characterized by a negative resistance characteristic
leading to decreasing potential between the cathode and
anode electrodes of the tube, a region of abnormal glow
discharge is entered in which the negative resistance
characteristic changes to a positive resistance
characteristic leading to increasing potential between the
electrodes. Typically this increased potential rapidly leads
to breakdown into vacuum arc discharge between the
electrodes, again characterized by a negative resistance
characteristic. Accordingly, gas discharge tubes have been
operated in the normal glow discharge or vacuum arc regimes
in which stable operation can be achieved by suitable
ballasting of the tube, the former regime being suitable for
low current applications and the latter for high current. It
is possible to utilize a normal glow discharge tube in a low
frequency oscillator circuit by placing capacitance in
parallel with the tube and in series with the ballast
because such a tube is characterized by a comparatively high
striking potential at which discharge is initiated, and a
lower but still high extinction potential at which discharge
ceases. Operation in such a mode with vacuum arc devices is
difficult because, in order to turn off the device
effectively, the arc must be extinguished or otherwise
interrupted or divested for long enough to disperse the
intense ionization formed in its path.
Devices operating in the vacuum arc regime
have other problems, particularly in terms of ensuring
adequate electrode life, which have led to gas diodes and
triodes (thyratrons) being superseded by semiconductor
devices in most applications. A further limitation of such
devices is that the great difficulty in turning them off,
except by terminating current flow through the device for a
finite period, limits their usefulness as control devices to
rectification, current turn-on and low frequency alternating
current applications.
The only prior art of which we are aware which
successfully exploits the abnormal glow discharge regime is
the process described in U.S. Pat. No. 3,471,316 (Manuel)
issued Oct. 7, 1969, which we understand is commercially
utilized in forming organic coatings on metal cans. It
relies on the application of externally generated current
pulses to force a discharge tube temporarily into the
abnormal glow discharge region, the pulses being
sufficiently short that no vacuum arc is established. There
is no disclosure of any endogenous pulsed abnormal glow
discharge, the apparatus is dependent upon an external pulse
generator to operate, and its utility is completely
different from the present invention because it uses
externally generated pulses rather than generating such
pulses.
We are also aware that the use of vacuum arc
discharge tubes has been proposed for the control of
inverters, as exemplified by U.S. Pat. No. 4,194,239
(Jayaram et al), which discloses the use of vacuum arc
discharge tubes in which the discharge is steered
magnetically between multiple electrodes to provide a
commutating effect. Such an arrangement acknowledges the
difficulty of extinguishing a vacuum arc, and seeks to
overcome the difficulty by instead switching the discharge
between electrodes by the use of externally applied magnetic
fields.
SUMMARY OF THE INVENTION
The problems associated with the operation of
vacuum arc devices are typically associated with the
establishment of a continuous channel of low resistance
ionized plasma between the electrodes of a device operating
in this mode, typically accompanied by intense heating of
the electrodes. Such a channel is difficult to interrupt in
rapid and predictable manner once established. The pulsed
abnormal glow discharge regime is characterized by no such
continuous channel having been established, and
predominantly cold-cathode auto-electronic emission rather
than thermionic emission, these characteristics provide the
ability to extinguish the discharge readily.
We have found that, by suitable design of a
low pressure gas discharge tube, we can sufficiently inhibit
transition from the abnormal glow discharge regime into the
vacuum arc discharge regime that we can successfully exploit
characteristics of the abnormal glow discharge regime to
provide a device having valuable and controllable
characteristics as a high power, pulse generator when fed
from a current source. Such a pulse generator has useful
applications in for example motor control and other
applications requiring high current pulses. It is a valuable
characteristic that the pulse repetition frequency can be
varied over a range, the extent of which itself varies
according to the physical characteristics of the tube and
the environment in which it is operated. According to
circumstances, the frequency may range as low as 10 pulses
per second or range as high as 10.sup.4 pulses, these
figures being exemplary only and not limitative.
The purpose of the present invention is to
provide a means to operate alternating current machines, and
in particular to derive useful electromechanical work from
any vacuum discharge tube capable of sustaining a stable
pulsed abnormal glow discharge (PAGD). The present invention
provides a simple circuit having at least two parallel arms:
a pulse generator arm containing the vacuum discharge and an
electromechanical arm which transduces electrical pulses
into mechanical energy. In the latter, the electromechanical
device is integrated into a reactive load presenting a
capacitance in parallel with the tube. The present invention
was specially devised to work with specific cold cathode
vacuum tube pulse generators as disclosed in the parent
application, using either diode or triode connections, but
the circuitry can be made to work with any suitable vacuum
device capable of being operated in an endogenous pulsed
abnormal glow discharge regime under cold cathode
conditions.
The advantage of using a spontaneous emission
self-pulsing device such as that described in the parent
application lies in the fact that the speed of an AC motor
and its torque can be varied directly by altering any of the
parameters that affect pulse frequency as described in that
application. Two of these parameters, parallel capacitance
and applied, constant direct current, are of particular
usefulness, since when all other parameters are the same,
the rate of pulsed abnormal glow discharge, controlling
motor speed and torque, can be made to vary as a function of
increasing current applied to the cold cathode device, for
any given discharge capacitance employed. This yields an
extremely simple method of motor speed control, particularly
suited to drive synchronous and induction AC motors from a
starting DC supply, but also generally applicable to any
motor, whether rotary or linear, whose speed or rate is
dependent upon the frequency of a pulsed or alternating
current. Rather than placing an alternating current machine
directly in the circuit containing the discharge tube, it
may be connected indirectly through a transformer or
synchro-transmitter system.
SHORT DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph illustrating the
current to voltage relationship exhibited by a notional
vacuum discharge tube;
FIG. 2 is a graph illustrating the
current to breakdown, extinction (PAGD) and sustaining (VAD)
voltages of a particular vacuum discharge tube;
FIG. 3 is a circuit diagram of a first
embodiment of the invention, using a single phase
permanent-split induction or synchronous capacitor motor
connected in parallel with a pulse generator using a vacuum
discharge tube configured either as a diode or as a triode;
FIG. 4 is a circuit diagram of a second
embodiment, employing two motors in series, and a triode
connected vacuum tube pulse generator;
FIG. 5 is a circuit diagram of a third
embodiment, employing two motors in series, and two vacuum
discharge tubes placed in series;
FIG. 6 is a circuit diagram of a fourth
embodiment, employing a two-phase motor, and two vacuum
discharge tubes placed in series;
FIG. 7 is a graph illustrating the
results of tests using the first embodiment of the
invention, using a permanent split capacitor induction
motor, showing how motor speed in RPM varies with the total
series value of the external capacitance placed in parallel
with the vacuum discharge tube by the electromechanical arm
of the circuit;
FIG. 8 is a graph illustrating the
synchronous RPM vs. pulses per second linear response, in
the circuit of FIG. 3, of a single phase, synchronous
hysteresis capacitor motor for four different series
capacitance values in the electromechanical arm of the
circuit and the maximum pulse rates obtained for each
combination;
FIG. 9 is a graph showing the rotor
blocked torque, measured by a rope and pulley method, of a
single phase, synchronous hysteresis capacitor motor in the
circuit of FIG. 3, as a function of the increasing direct
current input resulting in increased pulse rate;
FIG. 10 is a graph showing the rotor
blocked torque, measured by a rope and pulley method, of a
single phase, synchronous hysteresis capacitor motor both in
the circuit of FIG. 3 (as a function of increasing PAGD rate
due to the increasing direct current applied to the
circuit), and when run at AC line frequency of 60 Hz, torque
being shown in each case as a function of the rms volts at
the motor input;
FIG. 11 is a graph exemplifying how the
pulse frequency of a PAGD discharge is related to direct
current applied to the tube in the circuit of FIG. 1,
accompanied by curves showing the potential applied to the
tube and the power in watts drawn by the tube;
FIG. 12 is a graph exemplifying
variation in RPM, rms current drawn, input volts, and true
and apparent power (watts and volt-amperes) of a synchronous
motor in the circuit of FIG. 1, and under the conditions of
FIG. 9;
FIG. 13 is a graph showing the rms
volts per pulse per second at various pulse rates for two
different single phase capacitor motors (induction and
hysteresis) utilized in the circuit of FIG. 1;
FIGS. 14 and 15 illustrate two
configurations of inverter according to the invention which
may be utilized to drive alternating current devices through
a transformer;
FIG. 16 shows in simplified form a
variant of the circuit of FIG. 3 in which the discharge tube
is connected differently;
FIG. 17 shows a variant of the circuit
of FIG. 3 in which the electromechanical arm is a
synchro-transmission system.
FIG. 18 illustrates a pulse generator
having a glass housing and tetrode geometry;
FIGS. 19a and 19b illustrate central
cross sections of the pulse generator of FIG. 18, and a
modification thereof, respectively;
FIG. 20 illustrates a Fowler-Nordheim
plot of the Vx or Vs values for the PAGD and VAD regimes,
respectively, in a pulse generator excited with a
positive-polarity constant voltage DC power supply, the PAGD
and VAD values being shown respectively in closed and open
squares;
FIG. 21 illustrates a continuous
variation of NGD sustaining/PAGD extinction voltages
(Vs/Vx), from breakdown to glow extinction, with decreasing
pressure (at a rotary pump), in 4 pulse generators having
different plate areas but the same electrode material (H34
aluminum), the same gap distance and the same potential of
860 VDC prior to breakdown;
FIG. 22 illustrates a continuous
variation of PAGD frequency with decreasing gas pressure in
3 pulse generators having different anode and cathode plate
areas (16, 64, 128 cm2) but the same cathode material (H34
aluminum) and the same gap distance of 5.5 cm;
FIG. 23 illustrates a shift of the PAGD
regime to higher pressure regions during pumpdown with a
rotary vacuum pump in an argon atmosphere;
FIG. 24A illustrates the circuit used
in the tests that supplied data for FIGS. 2 and 20 to 23;
FIG. 24B illustrates the circuit used for test results
described in Example 10.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Throughout the following detailed description,
the same reference numbers are used to denote identical
elements present in more than one Figure.
The context of the invention in terms of
vacuum discharge phenomena will first be discussed with
reference to FIGS. 1 and 2. Referring to FIG. 1, which plots
the potential between the principal electrodes of a vacuum
discharge tube with increasing current, potential being
shown on a linear but arbitrary scale of voltage, and
current on a logarithmic scale in amperes, curve A, below
its intersection with curve B, represents a typical
relationship between current and voltage for cold cathode
discharges, including auto-electronic emissions, whilst
curve B represents a typical relationship for thermionic
glow discharges, including thermionic emissions. The
high-current intersection of the two curves at point E
represents a transition into the vacuum arc discharge (VAD)
region (curve C) with the establishment of a continuous low
resistance plasma channel between the electrodes.
It will be noted that curve A exhibits, with
increasing current from very low levels, an initially rising
voltage or "positive resistance" characteristic, through the
Townsend discharge (TD) region, a flat characteristic
through the constant discharge (CD) region, a falling
voltage or "negative resistance" characteristic through the
transitional region discharge (TRD) and normal glow
discharge (NGD) regions, to a minimum, before once again
rising to a peak of F and then falling to an even lower
minimum, equal to the sustaining voltage for a vacuum arc
discharge, through the abnormal glow discharge (AGD) region.
The rising potential over the first portion of the AGD
region is believed occasioned by saturation of the
electrodes by the glow discharge, which causes the potential
to rise until autoelectronic emission sets in allowing the
potential to fall again as the current rises further. In
practice, the increasing interelectrode potential following
saturation, and other factors such as electrode heating,
leading to thermionic emission, will tend in conventional
tubes to result in a premature transition from the AGD into
the VAD regime, following a curve similar to curve D shown
in FIG. 1.
The present invention relies on the use of gas
discharge tubes designed to avoid premature transition from
the AGD to the VAD regimes, and capable of being operated in
a stable manner in that region of the characteristic curve
of FIG. 1 extending between points E and F. Referring now to
FIG. 2, which plots test results for just such a tube,
constructed as described below with reference to FIG. 18 and
19, and shows, again on similar coordinates to FIG. 1
(except that the potential units are defined), the
extinction or sustaining potentials of the tube (the same
information as plotted in FIG. 1), together with the
breakdown potential (i.e. the potential required to initiate
the autoelectronic discharge). It will be noted that the
breakdown curve shows two discontinuous portions X and Y,
corresponding to the vacuum arc and abnormal glow discharge
regimes respectively. The intersection of curve X, and curve
Z representing the sustaining or extinction potential is
illustrative of the difficulties inherent in extinguishing a
vacuum arc discharge, since a decrease in current is
accompanied by a decrease in breakdown voltage until it
equals the VAD sustaining voltage which does not vary
greatly in this region. On the other hand, the combination
of a fairly high and constant breakdown voltage (curve Y)
combined with an extinction potential which rises with
decreasing current in the region E-F (see FIG. 1) of the
pulsed abnormal glow discharge regime means that the pulsed
abnormal glow discharge will be extinguished if the current
source during the tube operation ceases to be able to
sustain the increasing current required to maintain the
discharge as the potential between its electrodes drops, at
some current below the intersection of curves X and Z.
If the effective internal resistance of the
source is above some critical level, then as the current
through the tube rises, the proportion of the source
potential developed across the tube will fall until it
intersects the curve Z at a current below the intersection
with curve X, at which point the abnormal glow discharge
will self extinguish, and the current flow through the tube
will drop abruptly until the current through the tube
combined with the potential between its electrodes again
intersects the curve A in FIG. 1. This permits
reestablishment of a rising current through the tube
traversing the abnormal glow discharge region as the
potential across the tube rises to the peak F and then again
falls to a point short of E. Accordingly, under these
circumstances, a pulsed abnormal glow discharge will be
exhibited, accompanied by high amplitude current pulses
through the tube. It should be understood that the curves of
FIG. 1 are indicative of the static behaviour of a nominal
discharge tube under particular current and voltage
conditions, and are not fully indicative of the behaviour of
the tube under dynamic conditions in which tube current and
inter-electrode potential vary with time, nor with changes
of the many other factors which may influence tube
behaviour. In particular, the plasma effects generated in
various phases of tube operation require finite time to
form, reform or dissipate as the case may be, and in the
case presently under consideration this time factor,
combined with time constants of the external circuit in
which the tube is placed, are determinative of the pulse
frequency of the discharge.
The definition of any regime of electrical
discharge in a vacuum is usually presented as dependent upon
the major operational parameter being considered, i.e. upon
the variation of direct current passing between the primary
electrodes. For a given optimal vacuum (which must
necessarily be less than perfect) all gas electrical
discharge regimes can be presented as dependent upon this
parameter. FIG. 1 is such a presentation and the peak that
characterizes the abnormal discharge region means that
within this region, as the applied current is increased
linearly, the resistance of the vacuous medium in the tube
first increases with increasing current, only to
subsequently decrease, still with increasing applied
current, down to the minimum resistance value corresponding
to the sustaining potential of a "vacuum" arc (which is
somewhat above the ionization potential of the gas, or in
fact of the metal vapour, in the enclosure). As the
transition from a normal glow discharge into a vacuum arc
discharge is made either directly (in thermionic devices) or
indirectly, in cold-cathode conditions, via an abnormal glow
discharge that may be more or less precipitous, it is only
in the ideal diode and the ideal vacuum that both linear
functions (corresponding to the regimes that have a
sustaining potential) and nonlinear functions (corresponding
to the transition regions, such as the TRD and the AGD)
appear to depend exclusively upon the input current. In
fact, many factors affect the AGD, foremost amongst them,
pressure, plate distance and plate area. Hence the peak in
the curve of FIG. 1 is an idealized view of events.
This said, we are left with the experimental
observations and what they tell us. In this respect,
auto-electronic emissions characteristic of the pulsed
abnormal gas discharge (PAGD) regime can be seen to emerge
from the NGD, as the current is increased beyond the point
when the cathode glow has reached plate saturation (if the
current is not too low and the plate area not too large).
The same effect occurs when the pressure is
reduced and the current is kept constant at a suitable level
(neither too high nor too low, exact figures depending on
other factors such as gap distance and plate area, etc.).
If the current is increased further, in either
case, the PAGD regime fully emerges (in other words, in
pumpdown tests, the applied current also has to be
sufficient). In this regime the plate is not so much
saturated with a negative glow (which remains, but is
attenuated), but exhibits local concentrations of the plasma
that arise in a given area of the cathode as a function of
the auto-electronic emission mechanism. If the applied
current is increased in steps, a stage is reached at which
the extinction potential of the PAGD falls until it meets
the minimum potential of an arc discharge, as demonstrated
in FIG. 2. With reference to FIG. 1, this means that the
current-dependent variation of the PAGD in these devices
passes from a high to a low extinction potential or from a
high to a low electrical resistivity of the medium, and is
thus localized on the descending slope of the peak in FIG.
1. Expressed in terms of resistance characteristics, the
regime of the pulsed abnormal glow discharge spans, as a
function of applied current, a subregion in which a positive
resistance characteristic changes into a leading negative
resistance characteristic. The pulsed regime of the AGD is
only sustainable when the intensity of the applied current
is greater than that needed to rapidly saturate the plates
(but not so great as to set up VAD), the result being
development of auto-electronic emission with its associated
inverted cone-like discharge and a residual, faint glow of
the entire cathode (rather than a saturated NGD).
Each PAGD cycle begins as a singular emission
and performs a cycle of functions whose electrical
characteristics vary accordingly with time. During a
charging process (which eventually leads to emission), the
plate potential rises to a maximum at F (see FIG. 1), while
being limited by the maximum virtual value of the applied
current. Any substantial increase in the applied current is
blocked by the insulating properties of the intervening
medium (as if a very large resistance characterized the
device); in the discharge process, beginning with the
initiation of auto-electronic emission at F, conditions for
conduction across the (operational) vacuum are established
and, as a consequence, the resistance characteristic of the
device becomes increasingly negative until the extinction
potential is reached, at which point the glow discharge
ceases. This endogenous on/off behaviour is exactly what
characterizes the PAGD cycle.
Two boundary conditions arise. In the first
case, the available current is not quite enough to sustain
the PAGD. In this instance, full escape from the NGD regime
and the characteristics associated with its sustaining
potential will not occur, while any heating of the cathode
will eventually lead to the establishment of a
semi-thermionic cathode glow. In the second instance, there
is a risk of degeneration into a thermionic NGD or a VAD if
the available current is too high or sustained too long.
This degeneration will set in during the second phase of the
PAGD unit cycle, and may lower the resistance of the device
to the point of constant conduction of current across the
vacuum; the result is that the auto-electronic emission is
not quenched, as spontaneously happens in the PAGD.
Thereafter, extinction of the resulting VAD, which may be
promoted by a variety of factors is an unpredictable event;
if the current is available, the arc will burn for as long
as there is energy supplied and as long as there is cathode
material available to consume. A VAD in no way resembles a
regular, cyclic oscillator, which is the outstanding aspect
of the PAGD. Whilst an arc discharge is, like the PAGD, an
auto-electronic emission phenomenon characterized by
intermittences (the apparent constancy of an arc is the
result of the high frequency of these intermittences), such
an arc does not exhibit the regular or quasi-regular
cyclical nature of the PAGD, nor its inherent current
limiting characteristics.
In order that a stable pulsed abnormal glow
discharge (PAGD) as discussed above may be obtained, the
discharge to be utilized must be capable of repeated
excursions into the region E to F of FIG. 1. This entails
that the tube be constructed so that, as the tube operates
and the current through it rises, the potential across the
tube can reach the peak F in FIG. 1 and beyond, without the
abnormal glow discharge degenerating into a vacuum arc
discharge. This will be influenced, among other factors, by
the extent of thermionic emission from the cathode which
will itself be influenced by resistive heating of the
electrodes and their work function, as well as by their
separation and configuration, and the nature and pressure of
gas within the tube, as well as the presence of auxiliary
electrodes or probes. The influence of these various factors
is extensively exemplified below, with reference to the
description associated with FIGS. 18 to 24b, which
description; discloses tubes capable of sustaining PAGD.
Whilst the present invention is described with reference to
its use in connection with such tubes, it should be
understood that the invention may be implemented utilizing
any tube capable of sustaining a stable PAGD discharge
whether or not disclosed in our earlier application.
FIG. 3 shows a first exemplary embodiment of
the invention operating in the examples described with a
single phase permanent-split induction or synchronous
capacitor motor having a rotor R, stator windings 15 and 16,
and a capacitor 17. The motor is connected to terminals 13a
and 13e and via capacitors 10 and 11 to the electrodes of a
vacuum discharge tube 7, capable of producing cold cathode
abnormal glow plasma pulses and constructed in accordance
with the principles set forth in FIG. 18 to 24b and their
associated description. Motors with other characteristics,
such as single phase capacitor-start induction motors,
two-value (start and run) capacitor induction motors,
repulsion-induction motors, repulsion-start induction-run
motors, reluctance motors, universal motors, split phase
motors, two-phase induction or synchronous motors (wired as
single phase capacitor-run motors), or single phase rotor
input synchro-transformer generators could also be connected
to the same terminals 13a and 13a.
As shown in FIG. 3, the voltage source may be
either a line-fed DC power supply 1 (preferably constant
current), a DC generator 2 or a battery pack 3. For best
results, one of the latter two should be employed because
line-fed supplies will contain other parallel circuitry,
including an internal bypass capacitance and, unless they
are very well regulated, will leak alternating current from
the line which may influence the pulse rate or stability of
the PAGD discharge. The supply voltage and current may be
controlled by using methods known to those skilled in the
art, whichever source is used. With line fed power supplies
it is preferred to control the DC output by varying the
power input using the autotransformer method. With a DC
generator, the power output can be controlled directly by
varying the speed of the generator. With a battery, simple
control of input direct current and output pulse frequency
from vacuum device 7 is best achieved with a variable series
resistor 4. Diodes 5 and 6 prevent transients from the pulse
discharge from reaching the DC source.
The discharge tube 7 is shown in FIG. 3
connected in a diode configuration with cathode 8 placed
between rectifier 5 and capacitor 10 and the anode 9 placed
between rectifier 6 and capacitor 11, by virtue of a switch
22 being turned off (position NC). When switch 22 is turned
to position 13a' so that an axial member or probe 12 within
the tube is connected to the terminal 13a, the pulse
frequency increases by an amount depending on the parameters
of the circuit as a whole. In this configuration, the axial
member of the pulse generator functions as a plasma excitor
member, as it lowers the potential and increases the rate of
discharge by adding its spontaneous emissions to those of
the cathode. The same result obtains when switch 22 connects
axial member 12 to position 13e' instead, thus joining it to
terminal 13e.
The capacitors 10 and 11 are placed in
parallel with the reactive electrodes, with the motor 14 in
series between capacitors 10 and 11, but in parallel with
either the plates (diode configuration) or the axial member
and the cathode or anode (triode configurations) as the case
may be. For best results, it is desirable to have
capacitances 10 and 11 disposed symmetrically in the circuit
as shown in FIG. 3. An unbalanced circuit results when one
capacitor is absent, and anode counter-emissions become
frequent. Capacitance values for discharge capacitors 10 and
11 are determined as a function of the type of vacuum pulse
device employed and the nature and performance
characteristics of the AC motor 14 chosen. If the
capacitances are too small, the motor will not start nor
maintain rotation; if too large, the motor will not turn
smoothly or continuously, and spontaneous anode
counter-emissions may occur which will break the rotation of
the motor by reversing the direction of the electromagnetic
flux. The critical parameter is the total series value of
the capacitance placed in parallel with the pulse generating
device, and there is no need for the capacitances 10 and 11
to be identical; in fact it is preferred that there be a
higher capacitance on the side of the cathode (capacitance
10) than on the anode side (capacitance 11) when the triode
configuration has the axial excitor member connected to 13a
via switch 22 at position 13a', or the reverse when the
axial member is connected to 13e.
The AC motor employed may, in general, be of
any type. Split phase, single phase, or two phase AC motors,
be they universal, induction or synchronous types, having
squirrel-cage, wound-type, eddy current, drag cup or
hysteresis-type rotors, will all respond to the pulses
generated in this circuit. Single phase, permanent-split
capacitor, AC induction motors having squirrel-cage rotors
and single phase AC synchronous hysteresis capacitor motors
are preferred. The latter, in particular, have the advantage
of developing a nearly uniform torque from stationary or
blocked rotor positions to synchronous speed as well as
producing a smoother response to the pulsating nature of
single phase power (e.g. in a 60 Hz circuit, power is in
fact delivered in pulses at 120 Hz) than that of other
single phase motors. The motor 14 in FIG. 3 has its main
winding coil 15 in parallel with the discharge tube and an
auxiliary coil 16 connected in parallel with the main coil
15 via the phase capacitor 17. This corresponds to the
connection as a single phase AC permanent-split capacitor
motor. To reverse the direction of the motor it is
sufficient to switch the position of switch 18 from pole 19
to pole 20. If motor 14 were a suitable two phase AC
induction or synchronous motor wired as a permanent-split
capacitor single phase motor, then the reversal obtained by
switching 18 would provide an equal torque in either
direction of rotor rotation of the motor. A less efficient
start-up or phase displacement utilizes a resistance in
place of capacitor 17, in a manner known in the art. The
resistance may be varied to alter the motor speed.
Replacement of pulse generator 7 by a suitable
vacuum device, as diverse as a fluorescent light bulb (as a
diode) or a deuterium triode indicates that, despite the
absence of desirable physical parameters identified in the
parent application, any cold cathode operated vacuum tube
device capable of endogenous pulsed abnormal glow discharges
through spontaneous autoelectronic cathode emissions when
operated in the abnormal glow discharge region, is capable
of serving as the pulse-forming discharge tube in the
circuit. By contrast, whilst discharge tubes operating in
the normal glow discharge region can be used to form pulse
generators, the mechanism is different and the power output
would generally be too low to be useful in an
electromechanical application.
Any inductive AC electromechanical device such
as a relay solenoid or linear motor, may also be employed in
place of motor 14 at terminals 13a and 13e, FIG. 3, to
derive electromechanical work from the on and off switching
action of the vacuum discharge tube 7 when operated in the
abnormal glow discharge region.
An advantage of the invention is that a
constant current supply coupled to a suitable vacuum
discharge tube can be used to obtain smooth rotary action
from certain AC motors in an easily controllable fashion,
without having recourse to a conventional inverter system in
order to produce alternating current, and provides a simple
means of frequency control. Whereas the main limitation
imposed on the use of induction or synchronous AC motors is
that they are essentially constant speed motors which can
only vary their torque as a function of the magnitude of the
AC voltage and current input (given that the frequency of
the power supply cannot normally be changed), the present
invention allows the torque and speed of an AC motor to be
controlled by varying the DC voltage and current applied to
any cold cathode vacuum device 7 operated in the pulsed
abnormal glow discharge regime as discussed above, as well
as by varying the pulse rate of the vacuum discharge by
other means such as through the probe 12 in a device as
described in the parent application. Furthermore, the
electromechanical force is developed from a nearly even
sequence of discontinuous energy bursts, of controllable
frequency, rather than continuous sinusoidal power pulses at
a fixed frequency.
FIG. 4 shows how two single phase
permanent-split capacitor AC motors 14a and 14b may be
connected symmetrically in tandem, both placed in parallel
with a single vacuum discharge tube 7, following the
principles described above for FIG. 3. Independently of
whether the axial member 12 is or is not connected to
junction 13b, a capacitor 21 may be advantageously
introduced between junctions 13b and junction 13c, to even
out the rotation of the two motors, although it is not
essential.
FIG. 5 shows how two (or more) discharge tubes
may be connected in series to drive two or more motors 14a
and 14b also in tandem, from the output of two or more
vacuum devices 7 placed in series with each other.
Connections 13a' and 13d' from axial members 12a and 12b, as
well as capacitor 11 and its connection to 13b may be
omitted and the circuit will still function. The circuit of
FIG. 5 will produce a pulse sequence at the output from the
second tube which is phase shifted with respect to that of
the first tube, with further shifting as more tubes are
added. It is thus possible to couple multi-phase motors as
shown in FIG. 6, (showing a two phase motor) with a suitable
capacitance 21 being introduced between junction 13b and
junction 13c to control further the firing rate of the
second vacuum device 7b. The addition of more tubes in
series will further displace the phase of the pulse
sequences in each successive device. Sufficient relative
angular displacement of two tube-generated pulse sequences
can also be achieved by introducing a suitable delay relay
between points 23 and 24, at the cathode input to the second
vacuum device.
In general, the pulse frequency developed by a
discharge tube operated to produce PAGD in the circuits
described will depend on several factors: some are circuit
factors, such as the total discharge capacitance placed in
parallel with the vacuum device, and the characteristics of
the power supply (direct current and voltage values); others
are physical factors, such as the pressure, the chemical
nature of the gas fill and the field-emission work function
of the cathode material and its composition and still others
are geometrical or dimensional in nature, such as the
interelectrode distance, the plate area and the parallel
plate arrangement. All these factors are discussed in the
parent application.
The following examples relate to tests of the
circuit of FIG. 3.
EXAMPLE 1
The circuit of FIG. 3 was tested with a single
phase squirrel cage induction motor, the capacitor 17 being
2 .mu.Fd. The RPM of the rotor was measured with a
stroboscopic tachometer to determine how it varied with the
total series value of the external capacitances 10 and 11
(FIG. 3) placed in the electromechanical arm of the circuit,
in parallel with the anode and the cathode of a discharge
tube constructed as described with reference to FIG. 18,
with 64 cm.sup.2 plate area, 5.5 cm interelectrode distance
and an air fill at 2 Torr. The tube was excited in a triode
configuration (switch 22 at position 13a' and switch 18 at
position 19, FIG. 3) by an AC line-fed DC power supply. The
results are shown in FIG. 7. Provided that the capacitance
is not too high or too low, other factors such as the
frequency of the pulses generated by the vacuum device
(which increases with decreasing parallel capacitance) and
the type and characteristics of the windings and of the
rotor of the motor employed, have a greater influence on the
motor speed.
EXAMPLE 2
The total value (internal to the power supply
and external to it) of the capacitance placed in parallel
with the discharge tube in the same triode configuration of
the previous Example, in turn affects the maximum frequency
of abnormal glow discharge pulses produced, and the
effective synchronous motor RPM, as shown in FIG. 8. This
figure presents motor RPM as a function of the total series
value of the external capacitances placed in the
electromechanical arm of the circuit, and shows results
obtained with a single phase hysteresis capacitor motor
(rated as 110 VAC 1/10 Hp, with the auxiliary winding motor
capacitance 17 having a value of 2.4 microfarad). These
tests indicate that for any given AC motor there will be
optimal values for the pulse rate produced by the discharge
tube, and that this pulse rate will have a maximum value for
any particular value of the total capacitance placed in
parallel with the pulse generator, and specifically in the
electromechanical arm of the circuit, and this capacitance
itself will have an optimal value. Conversely, for any given
motor characteristics, a pulse generator can be designed
with optimized circuit or electrical, physical and
geometrical parameters.
EXAMPLE 3
With a rope-and-pulley type of torque meter,
the rotor-blocked torque developed by a synchronous
hysteresis motor was tested using the circuit of FIG. 3, and
the same vacuum device as the previous two Examples. This
type of motor was chosen because in an "ideal hysteresis"
motor, the torque developed is constant at all speeds from
standstill to synchronicity, locked rotor, pull-in and pull
out torques being identical. Even though a single-phase
capacitor-type hysteresis motor departs more from the ideal
curve than a polyphase hysteresis motor does, on account of
the elliptically shaped rotating fields set up by a
capacitor motor, most manufacturers make permanent-split
capacitor single phase hysteresis motors with identical
full-load and locked rotor torques. We have utilized one
such motor for our tests. FIG. 9 illustrates the range and
mean of at least nine tests conducted at each of three
different input direct currents into the pulse generator,
the extinction voltage remaining relatively constant at
about 330 VDC, with the results expressed as standstill
torque developed related to the pulse rate of the pulse
generator. The discharge tube was triode connected as
described with reference to FIG. 3, and the total series
value of the external parallel capacitance to the pulse
generator was 36.6 microfarads. It is readily apparent that
the torque developed is proportional to the pulse frequency
as is desirable for the purposes of the present invention.
The torque developed is also proportional to the voltage
input into the motor (i.e. the tube output voltage) as is
exemplified in FIG. 10, where tests of the PAGD-induced
torque (closed squares) obtained and measured under the same
conditions described for FIG. 10, over the frequency range
of 11 to 45 PPS, are compared with tests of an AC 60 Hz line
sine wave generated torque (shaded circles), as a function
of the input volts into the motor from each source.
EXAMPLE 4
An example of the relationship of operational
parameters involved in the performance of the circuit of
FIG. 3 is shown in FIGS. 11 and 12, using the same pulse
generator device employed in the previous Examples 1 through
3 at an air pressure of 1.75 Torr, and using the same
hysteresis motor as described in the previous Examples 2 and
3. The tests of FIGS. 11 and 12 utilized a total series
capacitance for the external electromechanical arm of 7.9
.mu.fd (with reference to FIG. 3: capacitor 10 = 440 .mu.fd,
capacitor 11=8 .mu.fd)). The same triode circuit was
employed as in previous examples. FIG. 11 illustrates how
the discharge rate of the pulse generator is controlled by
the steep increase in applied DC amperes (open squares)
while DC volts (closed squares) decrease to a near plateau
as the pulse frequency reaches 40 pulse per second. Total
wattage input to the discharge tube in the PAGD regime, at
the output from the transformer secondary of the DC power
supply, is shown in shaded squares. FIG. 12 shows the
corresponding pulse output from the vacuum tube into the
motor arm of the circuit and illustrates how the AC rms
current (open squares), the AC rms voltage (open circles),
the true and apparent power (respectively, closed and shaded
circles) as well as the rpm of the synchronous hysteresis
motor increase proportionately to the discharge rate of the
pulse generator. With reference to FIG. 3, the effect of the
connection to the axial member 12 through the switch 22 is
to promote, other conditions being equal, an increase in
discharge frequency: at these tube input and output
parameters changing from a diode to a triode configuration
typically increases the maximum discharge rate from 30 to
43-45 PPS.
With the triode configuration and all other
conditions being unchanged, the effect of a larger total
series capacitance value placed in parallel with the pulse
generator, in the electromechanical arm of the circuit, is
to limit the maximum pulse rate of the PAGD and the related
motor parameters, as illustrated by FIG. 8.
EXAMPLE 5
When a motor is wired as a single phase motor
and connected to an adjustable frequency power source, the
voltage applied to the motor stator terminals should change
proportionately to the change in frequency in order to
maintain the constant air-gap flux that permits the motor to
develop its rated torque over its speed range. A provision
is thus desirably made in the power source not only to
maintain a volts to pulse rate relationship which is
relatively constant over an operating range, but also to
maintain it at a value suited to the motor. In the present
invention this is easily accomplished by adjusting the total
series capacitance in the electromechanical arm of the
circuit to the set value of the operating motor for any
given input frequency range. Two such examples of volts per
pulse per second curves as a function of PAGD frequency at
the motor input are shown in FIG. 13, one (shaded circles)
obtained with a squirrel cage induction motor (110 VAC, 1/20
Hp, 2 mfd auxiliary winding capacitance) and the other (open
circles) with the same hysteresis motor used in the previous
Examples 2 through 4. Total series capacitance values for
the parallel electromechanical arm of the circuit were
respectively 3 and 8 mfd. In both instances shown, the volts
per cycle value tends to become a constant with increasing
frequency, reaching a plateau at around 25 PPS.
In some instances, it may be appropriate to
incorporate a discharge tube operating in the PAGD regime in
an inverter circuit so that the pulse output may be utilized
by a remotely located alternating current device. The
intermittency of the pulses produced by the arrangements
described above are not conducive to efficient operation of
conventional transformers, and a push-pull circuit
arrangement is preferred. While such an arrangement could
utilize two discharge tubes, an advantageous arrangement
utilizes a single tube of the type described in the parent
application, as shown in FIG. 14. In this instance, both
plates 8a and 8b of the tube act as cathodes and are
connected to the diode 5, and the probe or auxiliary
electrode, which is typically of tungsten, acts as a common
anode 9 and is connected to the diode 6. The capacitors 10a
and 10b are connected to opposite ends of a centre-tapped
primary winding of a transformer 26, providing an
alternating circuit output through a secondary winding. The
centre-tap of the primary winding is connected to the
electrode 9. The two halves of the primary winding
inductively couple the cathode circuits in antiphase, thus
synchronising the PAGD pulse trains involving the two
cathodes in antiphase.
In a modification of the circuit shown in FIG.
15, the capacitors 10a and 10b are connected directly to the
electrode 9, and the primary of the transformer 26 is
connected directly between the two cathodes with its centre
tap connected to the diode 5. Whilst this arrangement bears
some superficial resemblance to known inverter circuits
employing VAD devices, it should be noted that the circuit
is completely self-commutating, and does not need moving
external magnetic fields to provide commutation as in the
prior art.
It should be understood that, using a suitable
three or more phase transformer, and a vacuum discharge tube
with three or more cathodes (or three or more discharge
tubes), a higher pulse rate or a multiphase output may be
obtained from the transformer. It should also be understood
that, as shown in FIG. 16, in some applications it may be
advantageous to strap the plates 8a and 8b in parallel as
cathodes 8a and 8b and use the auxiliary electrode as an
anode 9, in a circuit similar to that shown in FIG. 3, the
tube being operated either in diode mode as shown, or in
triode mode utilizing an additional auxiliary electrode.
FIG. 17 shows a modification of the circuit of
FIG. 3. When the switch at node 13a is in position 25, it
provides pulses only to the rotor R2 of a self-synchronous
(selsyn) unit 27 in a synchro-transmitter system, in which a
three phase output of the unit 27 is utilized per se, or
transmitted to three phase windings of a second, slave unit
28, the windings of whose rotor R3 is closed through an
external short circuit or load. Whilst rotation of the rotor
R2 will provide synchronous rotation of the rotor R3 in
well-known fashion, it may be advantageous to place the
switch in position 24 to connect the motor 14, and to link
its rotor R1 to the rotor R2 to provide this rotation, thus
in turn providing remotely a corresponding rotation of rotor
R3.
FIGS. 18, 19a and 19b of the drawings
illustrate the construction geometry of discharge tubes
which may be utilized as pulse generators such as shown in
FIGS. 24a and 24b and in implementing the invention. The
discharge tubes are assembled using accepted techniques
which are well known to those skilled in the art of vacuum
tube technology.
FIG. 18 shows a pulse generator, generally
referred to by reference 50, having a cylindrical housing 52
which is preferably a glass material. Depending on the
interelectrode spacing of the pulse generator, which in
accordance with the invention may range from about 3 cm to
about 20 cm or more, the glass housing 52 is preferably
Pyrex.TM. or #7740 borosilicate (Corning, N.Y.). Such
cylindrical housings 52 are commonly available in diameters
of about 6 to about 11 cm and a variable thickness of about
0.2 to about 0.3 cm. Other borosilicate glass, quartz glass
or ceramic housings can be employed as suitable alternatives
to Pyrex glass and in sizes outside these commonly available
ranges.
The pulse generator 50 further includes two
parallel, spaced-apart electrodes comprising a cathode 54
and an anode 56, hereinafter often collectively referred to
as "plates" for brevity and convenience. As noted above, the
anode and cathode in pulse generators according to the
invention are spaced 3 to 20 cm or more apart. The cathode
54 and the anode 56 may be either flat or curved and are
preferably made of 0.5 to 2.0 mm thick aluminum, nickel or
nickel alloy. The thickness of the cathode 54 and the anode
56 is not critical and any thickness within a reasonable
range apparent to those skilled in the art may be used. The
surface areas of the cathode 54 and the anode 56 are
preferably quite large in comparison to the surface area of
an anode/cathode in prior art vacuum tube devices. Surface
areas which range from 16 to 256 cm.sup.2 have been tested,
as described in the examples hereinafter. Although the scope
of the invention is not believed to be limited by this range
of surface area of values, it was generally observed that
the larger the surface area of the anode/cathode tested, the
more readily the pulse generator 50 elicited PAGD discharges
providing other conditions such as plate material, vacuum,
residual gas fill, voltage and current remained constant.
The preferred material for the cathode 54 and
the anode 56 is aluminum. Two specific types of aluminum are
preferred; namely, H34 rolled aluminum available from the
Alcan Company and Alzak.TM. aluminum available from the
Alcoa Company. Other types of aluminum are assumed to
constitute suitable material for cathode 54 and anode 56.
Aluminum is a preferred material because of its low work
function for field emission as well as for its other
qualities such as relative freedom from sputtering, except
when subjected to vacuum arc discharges, and its electrical
conductivity. In all instances, the aluminum used for
cathode 54 and anode 56 were degreased and rinsed in
accordance with published methods familiar to those skilled
in the art.
Each of the cathode 54 and anode 56 is
suspended within housing 52 by a support member 58 which
passes through hermetic seal 60 an opposite sides of the
housing 52. The support members 58 are preferably rigid rods
of substantially pure tungsten in a diameter of 1/16 th to
3/32 nd of an inch, or any suitable diameter. The material
of choice is round finished PureTung.TM. available from
Union Carbide.
The pulse generator 50 also includes at least
one axial probe 62 and the pulse generator 50 shown in FIG.
18 has a tetrode geometry with two spaced-apart axial probes
62. Substantially pure tungsten rod is also the preferred
material for constructing the axial probe(s). All tungsten
rods used in assembling pulse generators in accordance with
the invention were repeatedly cleaned with sodium nitrate
and fused with a beaded sleeve of uranium glass #3320
available from the Corning Company or nonex.TM. glass #7720.
These glasses are graded seals designed for high vacuum
tungsten/pyrex junctions. Before the metal components of the
pulse generator 50 are introduced into the glass housing 52,
the housing is annealed at a temperature of 565.degree. C.
After the pulse generator was assembled, it was connected by
a glass constriction tube to the glass manifold of a vacuum
system (not illustrated).
An alternative geometry for a pulse generator
in accordance with the invention includes a
parallelepiped-shaped housing which is assembled using a
suitable plastic polymer sheet. Polymer housings are
preferably made from polycarbonate, specifically Lexan.TM.
available from the General Electric Company. Especially
preferred are the ultraviolet resistant Margard.TM.
surface-treated Lexan.TM. MR5 or superior grades. The joints
of the rectangular panels are preferably sealed with either
a low vapour pressure resin Torr Seal.TM. available from the
Varian Corporation which is applied along the mating edges
to glue the panels or alternatively, an epoxy putty such as
LePage's or MR Carbone's Handworkable Putty is first layered
over the joints and then covered with translucent
Scotch-Weld epoxy resin 2216B/A available from the 3M
Company or another adhesive system suitable for withstanding
the implosive forces of very high vacuum. For very large
housings the walls are also preferably screwed together at
spaced-apart intervals. Non-metallic internal braces can
also be used to reinforce very large housings. The
polycarbonate housings are cleaned as per manufacturer's
instructions and all metal to polymer support interfaces,
such as the hermetic seals where electrodes and probe(s)
pass through a side wall of the parallelepiped-shaped
housing are preferably epoxy resin joints made with Torr
Seal.TM.. The vacuum constriction for connecting the housing
to a vacuum pump is made of glass which is also joined to
the polycarbonate surface using the Torr Seal.TM. epoxy
resin. This alternative construction of pulse generator has
a triode geometry which includes a single axial probe made
of substantially pure tungsten rod. In all other respects it
is the same as the pulse generator 50 described with
reference to FIG. 18.
FIGS. 19a and 19b show transverse
cross-sections of preferred constructions of pulse
generators in accordance with the invention. FIG. 19a
illustrates a cylindrical housing 52 with a flat plate anode
56 and cathode 54. As shown in FIG. 19b, the anode 56 and
the cathode 54 may be elongated, transversely curved
sections which are substantially semi-cylindrical in shape.
This anode/cathode geometry is actually preferred for
cylindrical housings. The curved electrodes may be made from
laser quality reflective aluminum foil about 200 microns in
thickness. Such electrodes have a current tolerance of
approximately 100 mA of direct current in the PAGD regime
and are destroyed by disruptive slippage into arc discharge
with as little as 900 watts of applied power. Curved
electrodes of press-formed aluminum plate are therefore
preferred over curved electrodes made from aluminum foil.
The following examples of tests conducted with
discharge tubes 50 used as pulse generators illustrate the
character and performance of such pulse generators.
EXAMPLE 6
Volt-ampere Characteristics of a Pulse
Generator
The tests described in this example were
conducted with a pulse generator 50 (device #1) constructed
with H34 aluminum flat plates (128 cm.sup.2 area) set 5 cm
apart, and equidistantly from a continuous axial probe 62 in
a vacuum which measured 10.sup.-6 Torr at time of seal off.
FIG. 2, already discussed above, shows that under conditions
of a positive, constant DC voltage applied to the anode 56
of this device, the volt-ampere curve for both breakdown
potential (Vb, shown as open squares) and for the minimum
discharge potentials (Vs, or VAD sustaining potential and
Vx, or extinction PAGD potential, both shown as closed
circles) disclose two regions or regimes in the operation of
this device, a region of pulsed AGD which spanned from about
10 mA to about 150 mA RMS (with an applied maximum of 15 mA
DC average), and a region of VAD at RMS current values
greater than 250 mA. PAGD current data was derived from peak
pulse RMS values and VAD RMS current data was obtained at
steady-state. Within the range of the pulsed AGD, the Vb
values were high and plateaued at about 850 volts; Vb values
for the VAD regime were generally lower than those of the
PAGD and could be raised by an increase in available
current.
A PAGD regime could also be equally identified
when the supplied DC voltage was negative and applied to the
same cathode plate 54 (see FIG. 18), for both PAGD and VAD,
Vb and Vx values (closed and open squares, respectively) at
comparable transduced pulse RMS currents. Utilizing a
10-fold higher direct current power supply, also
earth-grounded at the centertap but having a parallel supply
capacitance of 55 mfd and a slow voltage recovery rate (ie.
less than 200 V/sec), the same pulse generator 50 (device
#1) yielded 10.times. higher peak PAGD RMS currents (2 A vs.
200 mA) than were obtained under the same conditions and
with the same power supply by a positive applied voltage of
equal magnitude. These findings suggest that, at high
applied direct currents, there is a strong asymmetric
response of the pulse generators 50 (larger PAGD RMS current
values with cathodic tension than with comparable anodic
tension) with respect to the sign of the plate polarization
in reference to earth-ground.
It is also apparent that the field emission
responsible for the PAGD regime does not obey the
Fowler-Nordheim VAD region law (see FIG. 20): whereas the
VAD graph has the expected negative slope, the slope of the
PAGD graph is positive, contrary to predictions by the
Fowler-Nordheim VAD region law. This constitutes strong
evidence for the existence of auto-electronic emission
discharges that do not obey the behaviour predicted by the
Fowler-Nordheim field-emission theory, the discharges
occurring at much lower currents than predicted by that
theory.
EXAMPLE 7
Pulse Count Rates in the PAGD Region
Two pulse count studies were done: a first at
low applied direct currents (<1.5 mA) and a second at mid
to high applied direct currents (1.5 mA to 200 mA). Peak
pulse RMS currents during the second study were as high as 2
A.
At low currents, using the pulse generator 50
(device #1) assembled with H34 aluminum plates and ballasted
with a 1 Mohm resistor and a lower pulse amplitude detection
cut-off at less than 25V, the pulse per minute counts at the
axial probe were observed to increase as the anode-supplied
voltage (and the current, not illustrated), was incremented
from 300 V to 500 V. At higher voltages the pulse count
plateaued at a somewhat depressed level. Conversely,
utilizing a pulse generator (device #2) assembled with Alzak
plates in an identical vacuum at seal off (10.sup.-6 Torr),
the pulse counts increased with applied voltage up to a
maximum voltage applied, the maximum pulse count being about
9 times higher than observed with device #1. Reducing the
ballast resistance increased the pulse rate of device #1 to
a maximum of 1000 pps, or 60,000 PPM with a 0.125 ohm
resistor, and increased the pulse rate of device #2 to 4000
pps or 240,000 PPM. Analysis of the pulse signals with an
oscilloscope showed that, in both instances, the observed
CPM values at the axial probe 62 effectively corresponded
(about 1:1) to the PPM values at the cathode 54, under these
conditions for both devices #1 and #2.
At currents higher than 1.5 mA, when the PAGD
regime is fully active, the inverse phenomenon was observed:
i.e. the pulse rates increased with a decrease in the value
of the extinction voltage (Vx). They also increased
proportionally to the transduced pulse RMS current. This was
observed for both positive and negative polarizations of the
`vacuum`, with pulse generator 50 (device #1) Under these
conditions and with a 1 Mohm ballast resistor, rates of
113-124 pps were measured, the limiting factor being the
recovery time of the voltage regulation of the power supply
as the current drain increased. This phenomenon was
exaggerated when no ballast was employed and the largest
peak pulse currents were observed. With faster recovery
power supplies capable of delivering the same or higher
input currents (and having the same large value of
capacitance in parallel with the plates) much higher pulse
rates (greater than 1,000 pps) could be obtained, along with
larger peak pulse RMS currents.
EXAMPLE 8
Detection of the PAGD Region in the Pulse
Generator as a Function of Decreasing Pressure
Argon pumpdown tests were conducted to
determine whether and when the PAGD region of the discharge
was apparent utilizing comparably low voltages (up to 2.5
kv). These tests were performed with both the diffusion pump
off and on. FIG. 21 shows a typical curve of the variation
of the sustaining/extinction voltages at the plates with
decreasing pressure at the rotary pump, from breakdown (at
860 VDC) to glow extinction, for all four pulse generators
50 examined (device #'s 3 to 6), which were assembled with
H34 aluminum plates having different electrode areas: device
#3, 16 cm.sup.2 (small closed squares); device #4, 64
cm.sup.2 (open circles); device #5, 128 cm.sup.2 (open
squares); device #6, 128 cm.sup.2 (large closed squares).
Each pulse generator 50 had the same gap distance of 5.5 cm
and was assembled with the same volume of glass envelope.
Devices #3 to 5 were evacuated simultaneously and an
identical average direct current of 1 mA was applied to each
separately, using comparable power supplies ballasted with a
1 Mohm resistor. Device #6 was evacuated in a separate test,
under the same pumpdown conditions and at the same applied
potential of 860 VDC at breakdown, but was subjected to a
100-fold higher, average direct current of 500 mA. It is
readily apparent that the continuously varying,
sustaining/extinction voltage curves shown in FIG. 21 are
analogous to the Paschen gas breakdown voltage curve
and that throughout most of the voltage range all
three low current curves are parallel. Independent
determinations of the low current breakdown voltage curves
for all three pulse generators 50 (devices #3 to 5) showed
the exact same relation for all three curves as observed for
the sustaining/extinction voltage curves (results not
shown). The differences between the electrical discharge
regimes observed as a function of decreasing pressure are
most apparent in the larger plate area pulse generator 50
(device #5). The three regions of the discharge, the
transitional glow, the normal glow and the pulsed abnormal
glow, are clearly distinguishable for that device (see FIG.
21). In the transitional region discharge (TRD), the cathode
glow is of minimal point-like size and rapid oscillations of
the striations of the plasma positive column originate
quasi-sinusoidal, dampened sinusoids, ramp-like or
noise-like waveforms associated with sporadic, small
amplitude (2 to 15 volts), pulsed auto-electronic emissions.
In this region the voltage tends to fall, while oscillating
erratically at first. As the pressure further decreases,
there follows a stable normal glow discharge (NGD) region,
where conduction of different current across the vacuum
pre-empts the possibility of auto-electronic emission the
lowest voltages are observed in this region. After the
recession of the positive column and upon glow saturation of
the plate areas, just as the cathode glow is beginning to
recede (pre-Cooke's `post-cathodic` phase), the intense,
large amplitude (>100 V), pulsed auto-electronic emission
characteristic of the PAGD regime emerges. In this region,
the voltage tends to climb until extinction occurs before
the maximum voltage of 860 V is again attained. In the other
two devices, the borders of the discharge regimes are
blurred. In device #3, the low emissions intensity, small
amplitude auto-electronic develop into a few high intensity,
large amplitude emissions, as they decrease in frequency and
with considerable overlap; the PAGD and NGD regimes are also
mostly mixed, until lower pressures of the order of 0.01
Torr are attained, at which point the PAGD regime functions
alone at low frequency. In device #4, the NGD regime can be
better distinguished from the TRD, and the PAGD from the
NGD, but high intensity, large amplitude auto-electronic
emissions occur early on in the NGD region as the glow
saturates the plates faster than for device #5. There is a
dual effect on increasing the average applied direct current
100-fold (device #6, large closed squares, shown in FIG.
21): the entire ascending arm of the voltage curve is
displaced upward in the pressure scale and the distribution
of the voltage variation is compressed. The high applied
direct current also abrogates the two discharge regions
adjacent to the PAGD. From breakdown to extinction, the
regime of the discharge is solely that of the PAGD, the
positive column of the discharge weakening with the
decreasing pressure. However, if the cathode is hot enough,
a quasi-thermionic `post-cathodic` glow may also briefly
occur after the PAGD regime and before glow extinction.
FIG. 22 shows the pulse rates for the observed
intense large amplitude, auto-electronic emissions
characteristic of the PAGD regime, which correspond to the
voltage curves for devices #3 to 5 obtained above as
described for FIG. 21. In all three devices, the PAGD regime
first appeared mixed together with the NGD regime in the
form of pulses that perturbed the steady-state glow, the
pulses increasing in frequency with the decreasing pressure
until a maximum pulse rate was attained.
In FIG. 23, the effect on the PAGD regime of
increasing the current 500-fold (from 1 to 500 mA), while
keeping the potential constant using the same 128 cm.sup.2
plate area pulse generator 50 (device #6) during two other
separate evacuations with the rotary pump, is shown. The
higher current displaces the PAGD region upward in the
pressure scale, just as was observed in the ascending arm of
the voltage curve (see FIG. 21). The displacement inducted
by the applied high current occurs over a pressure range
where, at low current (1 mA) and with the same applied
potential at breakdown, some weak, low-amplitude, pulsed
auto-electronic emissions are observed during the TRD.
The effect of increasing the starting DC
voltage at breakdown by 1.75-fold (from 860 to 1507 VDC) was
observed using device #3 in two separate tests. The
increased current displaced the PAGD upper pressure limit
downward in the pressure scale, in opposition to the current
effect and it also increased the frequency of the intense,
large amplitude, auto-electronic emissions by a factor of
about 8.8.
Using the same applied low direct current and
potential magnitude at breakdown (860 VDC) described for the
tests represented in FIGS. 21 and 22, pumpdown of the three
different plate area pulse generators 50 (each having
interelectrode distances of 5.5 cm) was performed with the
oil diffusion pump on. While the effect of increasing the
plate area under these conditions remained the same, i.e.
lowering the pressure for the same sustaining/extinction
potential and displacing the PAGD region to regions of
higher vacuum, there was a noticeable difference compared
with the same test done with the rotary pumpdown: i.e. the
extinction pressure was greatly extended downward in the
pressure scale for all devices, and, consequently, the PAGD
region was greatly expanded into the medium to high vacuum
ranges. A 128 cm.sup.2 plate area pulse generator 50 with
5.5 cm gap, (devices #11 and 12) typically reached PAGD
extinction at 5*10.sup.-5 Torr, though its peak pulse rate
remained basically unchanged. This overall displacement of
the PAGD phenomenon to higher vacuum regions under
conditions of oil diffusion evacuation may well be due to
the migration of very low vapour pressure oil molecules to
the tube ends (despite the baffle and the cooling trap) and
their interaction with residual gas molecules in the
electrical field of the devices. With the diffusion pump on
and voltages progressively increasing up to 2.5 kV with
decreasing pressure, the PAGD regimes in these pulse
generators 50 operated from 10.sup.-3 to 10.sup.-5 Torr.
Typically a 128 cm.sup.2 H34 aluminum plate pulse generator
50 (5.5 cm gap) will operate in the PAGD regime at
2*10.sup.-5 Torr, with an applied voltage of 2.2 kV and at a
pulse rate of 30 pps. With higher vacua (<10.sup.-5 Torr)
and voltages, the `post-cathodic` PAGD gives way to the
production of cathode rays and very weak x-rays. From
several such diffusion pumpdown tests it was concluded that
the PAGD was facilitated by the use of Alzak electrode
material and, as it will be shown in Example 9, by larger
plate areas.
EXAMPLE 9
The Effect of the Plate Area on the PAGD
Characteristics during Pumpdown
The effect of increasing the plate area of the
cathode 54 and anode 56 of a pulse generator 50 was tested
by two methods: 1) using a pumpdown method of varying the
vacuum with a rotary pump (as explained below) and 2) using
sealed housings 52, 64 enclosing a vacuum of 2*10.sup.-6
Torr obtained with the diffusion pump (see Example 10).
The results from the first test is shown in
FIGS. 21 and 22, for the pulse generators 50 stimulated with
low (1 mA) direct currents, at the same starting potential
of 860 VDC at breakdown. A comparison indicates that the
effect of increasing the plate area in pulse generators 50
having the same gap distance, and thus the same pd value
(pressure, in Torr, multiplied by interelectrode gap
distance, in cm), and the same volume, is to depress the
voltage, particularly in the NGD and PAGD regions and to
displace the auto-electronic pulsed emission characteristic
of the PAGD regime to a higher vacuum range. The peak
frequency of PAGD for each given area is also attained, in
each case, at a vacuum that increases proportionately to the
order of increasing area (16.fwdarw.64.fwdarw.128 cm.sup.2)
as does the magnitude of the peak frequency of PAGD for a
given gap distance. The distribution of PAGD frequencies
also narrows its characteristic mode with the larger area
plates, by displacing an upper pressure limit to lower
pressure regions, the most significant shift in this respect
being from the 64 to the 128 cm.sup.2 devices (FIG. 12, open
circles vs. open squares). This distribution compression
shift corresponds to a better definition between the NGD and
the PAGD regimes afforded by the pulse generator 50 with the
largest plate area employed (128 cm.sup.2), as discussed
above in Example 8. Moreover, in accordance with Paschen's
law, the observed area-dependent voltage reduction effect
cannot be explained, inasmuch as the voltage is predicted to
remain the same as long as the product pd is constant even
if the plate area increases. Since the interelectrode gap
distance was constant for all devices and as the pumpdown
was also performed simultaneously, it is apparent that there
is an electrode plate area effect which is not accounted for
by Paschen's law. The observed plate area effect appeared to
have an effect opposite to current and in the same direction
of increasing potential, as it displaced the PAGD region
downward in the pressure scale and increased the PAGD
frequency. In addition, an increase in area also reduces the
magnitude of the potential. From the results obtained, it is
apparent that an increase of 1.75 fold for a given breakdown
potential of a 16 cm.sup.2 pulse generator yields the same
pulse rate (about 60 pps) as does an 8 fold increase in
plate area for the same volume housing (52, 64), but
requires a lower pressure.
A comparison of breakdown order and pressure,
as well as of peak pps values and peak pps conditions
carried out as a function of plate area for the pulse
generators 50 (devices #'3 to 5) represented in FIGS. 21 and
22, showed that the pulse generator 50 with the largest
plate area, which was the first to undergo breakdown (during
six separate tests) at the highest pressure of 3 Torr,
yields an 8 fold higher PAGD rate than the pulse generator
50 with the smallest plate area of 16 cm.sup.2, at the
lowest pressure (the pressure is 24 times lower than that of
the 16 cm.sup.2 device). This peak pps rate occurs, however,
at a voltage which is about 9.5% greater for the pulse
generator 50 with the largest plate area. These results
suggest that a larger plate area promotes breakdown at
higher pressures (i.e. the breakdown pressure decreases
inversely to the order of increasing plate area) and
supports lower sustaining/extinction voltages.
In conclusion, the effect of increasing the
plate area of pulse generators stimulated with the same
starting voltage and the same current is to: 1) shift the
breakdown pressure upwards, 2) depress the working voltage,
3) increase the pulse rate both in the TRD and the PAGD
regions, 4) shift the PAGD region downwards in the pressure
scale and segregate the discharge regimes more clearly as a
function of decreasing pressure. These observations also
explain why the pulse generators with smaller plate area
shift the PAGD up in the pressure scale, as an increase in
current does. Effectively, a smaller plate area not only
concentrates the lines of electrostatic force in a vacuum,
but it also increases the current density per unit area,
with the consequent glow saturation of the plates, necessary
for the abnormal glow discharge region to be attached,
occurring earlier on during pumpdown, than for pulse
generators with larger plate areas.
EXAMPLE 10
The Effect of Plate Area on the PAGD
Characteristics of Pulse Generators Enclosing a High Vacuum
The second method used to test the effect of
increasing the electrode plate area in the design of a pulse
generator 50 made use of glass housings 52 enclosing a final
vacuum of 2*10.sup.-6 Torr obtained with a diffusion pump
on. These tests were performed with high direct currents
(200 mA to 1 A). All pulse generators tested (devices #'s 7
to 13) had an interelectrode gap distance of 5 cm, enclosed
the same volume and the same vacuum, and were assembled at
H34 aluminum plates having plate areas which varied by an
area factor of k.sub.A =2, namely: 64, 128 and 256 cm.sup.2.
Originally the test was performed with a series with a
k.sub.A = 2.sup.2 factor, the plate areas being described by
2.sup.4, 2.sup.6, 2.sup.8 or 16, 64 and 256 cm.sup.2.
However, at a seal off vacuum of 2*10.sup.-6, the first two
pulse generators 50 of this series (16 and 64 cm.sup.2,
devices #'s 7 to 10) remained unresponsive (no signs of
discharge). Even when 3.3 kV was applied, one of the 64
cm.sup.2 pulse generators showed only a faint glow (also see
discussion of results for groups #1 and #4 of Table 5
below). The results for the k.sub.A =2 series indicate that
when the current, the interelectrode distance and the
pressure are all kept constant, the breakdown potential (Vb)
for the PAGD decreases with an increase in plate area. For
the largest plate area tested (256 cm.sup.2), the PAGD
breakdown (287 V) and extinction (Vx=284 V) voltages
practically coincide, suggesting that larger areas might
depress both Vb and Vx still further. These results were
recorded under identical conditions of applied direct
current (200 mA), of peak pulse RMS current and of pulse
frequency (20 pps) using an earth-grounded centertap power
supply with both positive and negative voltages applied
simultaneously to the respective plates. Under the same
conditions of applied total power same starting voltage, but
higher applied direct current because of their lower
sustaining/extinction voltage), three pulse generators 50
built with Alzak plates having areas of 64, 78 and 128
cm.sup.2 respectively were tested with the same power
supply.
These pulse generators conduct 5-fold higher
DC currents, transduce 3-fold higher peak pulse RMS currents
and yield a 20 to 30-fold increase in pps (from 20 to 600
pps) at similar field strengths, when compared with the
results obtained using hardened aluminum plates.
A comparison of pulse counts at the axial
probe 62 (see FIGS. 18 and 19) in pulse generators 50 and
the pulse counts at the cathode 54 showed that the axial
probe 62 accurately reflects interelectrode events. This
correspondence was confirmed using oscillographic analysis
of the probe waveform, which showed it to be functionally
equivalent to that measured at the cathode 54.
Typically, for a closed high vacuum pulse
generator 50 with a plate area of 128 cm.sup.2 and an
interelectrode gap of 5 cm, a breakdown voltage of 668
volts, an average applied current of 500 ma, and at 200 pps,
the pulse amplitude is more than 300 volts. Under rotary
pumpdown conditions and for an identical pulse generator,
the pulse amplitude (encompassing both positive and negative
components, the latter being the prominent value) increases
with decreasing pressure, from 60 volts at about 0.5 Torr
(with 5 mA DC) to >300 volts at 0.008 Torr. In the closed
high vacuum pulse generator with H34 plates having an area
of 128 cm.sup.2 (device #1), higher resolution oscillographs
taken at the axial probe 62, show that the negative
component precedes the positive reversal and has a typically
higher amplitude (140 V vs. 80 to 120 V, respectively, for
example). Clearly, upon an abnormal glow discharge pulse,
the recovery of the field strength within these pulse
generators overshoots a `closed switch state` (where the
current I.about.O) and results in a net flow of positive
charge past the probe, towards the cathode (which is the
floating ground reference level for these measurements).
EXAMPLE 11
Effect of Capacitance on PAGD Rate
Using the same breakdown voltage of about 668
VDC, the effect of varying the capacitance of the power
supply, set in parallel with the pulse generator (device
#1), on the frequency of PAGD production was determined
while maintaining all other variables constant
(interelectrode gap, plate area, applied voltage and current
levels). Linear regression shows that, under these
conditions, the PAGD frequency is increased by lower
capacitances. The log slope indicates that the pps rate is
doubled as the capacitance decreases by 2/3 rds.
Measurements were also taken of the `non-dynamic`
capacitances of pulse generators with H34 aluminum plates
having different plate areas. These were insignificant when
compared with the parallel capacitances used in the power
supply , used in the tests, and were observed to vary in
accordance with the dielectric law, i.e. doubling the plate
area doubled the capacitance. This can be seen in the Table
below:
______________________________________
Plate
area:
Capacitance:
______________________________________
64
cm.sup.2
1*10.sup.-12 F
128
cm.sup.2
2.05*10.sup.-12 F
256
cm.sup.2
4.1*10.sup.-12 F
______________________________________
Optimum Arrangement and Geometry:
Prolonged operation of the pulse generators 50
has provided the geometries for eliciting PAGD production
including:
1) It is advantageous if the discharge does
not wander to the back of the anode 56/cathode 54 and this
is facilitated by using semi-cylindrical anode 56/cathode 54
in cylindrical housings 52 and flat anode 54/cathode 56
(rectangular, square or circular) in parallelepiped-shaped
housings. However interelectrode gap tests are best done
with flat plates which assure an homogeneous potential.
Moreover, the semi-cylindrical electrodes are best made of
hardened aluminum, at least 0.5 to 1 mm thick, and this
requires forming them to the right curvature, given that
foil alternatives are not resistant to the deleterious
effect of high-current PAGD transduction at very high
frequencies and do not withstand disruptive VAD discharges.
Nonetheless, a semi-cylindrical electrode configuration in a
housing 52 makes the sheaths (where ionic recombination
occurs during glow discharge) near the electrodes and the
housing wall coincide, and this can be highly advantageous
for sustaining PAGD production. The same applies to flat
plates in flat surface parallelepiped housings.
2) The most effective axial probe 62 is either
a single half-length rigid rod or a pair of axial probes 62
separated at the center of the pulse generator 50 by a gap
of more than 1 cm, 4-6 cm being optimum. Whereas an axial
wire will perform satisfactorily as a probe 62, the rigid
rod has the advantage of not yielding to a direct mechanical
transduction of the electrodynamic force effected upon it by
the discharge or to force created by the acquisition of a
constant space charge. A split axial probe 62 facilitates
the exciter function and assures PAGD operation by
preventing a formation of a stable axial space-charge at
high-current operation.
3) A cooling coil (made of rubber, polymer,
glass or copper tubing) surrounding housing 52 is useful to
counterbalance the heating of the anode 56/cathode 54 which
promotes the production of semi-thermionic VAD channels and
even thermionic normal glow discharges, specifically at
applied currents of more than 200 mA during PAGD operation.
A coolant pipe system that weaves through the plates can
also be used for this purpose, in which case flat plates are
preferred.
4) Larger anode 56/cathode 54 surfaces are
required as the interelectrode gap is increased. And
inversely, larger anode 54/cathode 56 surfaces operate best
(i.e. require the lowest applied voltages) if larger
interelectrode gaps are used; however, the breakdown voltage
also increases with larger interelectrode gaps.
5) One of the limitations of these pulse
generators stems from their continuous operation at high
applied currents and from eventual slippage into the VAD
regime, both of which promote a deposit of sputtered metal
atoms on the inner walls of the housing 52 thereby making
them conductive. In order to minimize this problem,
electromagnets may be wound longitudinally over the housing
52 (one at each end), to limit the dispersion of the
discharge vortices.
Factors Affecting PAGD Production:
It is apparent that several factors affect
PAGD production namely: cold cathode work function, voltage,
current, parallel capacitance, gas fill, pressure, geometry
plate area and interelectrode gap distance. Except for
capacitance at the high end of the scale, each of these
factors affect the high and low limits of the PAGD, for any
given set of conditions. Heretofore, factors such as plate
area in vacuum tubes have not been previously identified as
factors which affect the breakdown field values and the
sustaining/extinction potentials of a glow or an arc
discharge. This suggests that the observed auto-electronic
field emission in the PAGD regime is a function of physical
factors which to date have been unrecognized. It further
suggests that field emission is not a property exclusive to
the VAD, i.e. that it is also a property of the pulsed
operation of an abnormal glow discharge in low to very high
vacua.
The present pulse generators 50 provide an
optimal design capable of transducing high peak pulse
currents at very low field strength, over a wide range of
frequencies with minimal slippage of the PAGD operation into
either the NGD or the VAD regimes.
In conclusion, we have disclosed a series of
low to very high vacuum pulse generators which support the
production of PAGDs. In testing these devices we have shown
that:
the low field strengths and typical low
emission current densities observed in the PAGD regime are
not predicted by any existing field emission or space-charge
theories;
the PAGD regime responds asymmetrically to the
polarity of the applied voltage at high applied currents;
at low applied currents, the PAGD pulse rate
increases with the applied voltage and the current up to an
observed plateau;
at mid to high applied currents, the PAGD
pulse rate increases with an increase in current and with a
lowering of the extinction potential;
the PAGD pulse rate also varies with the
composition of the cathode material (the pulse rate is
promoted by materials having a low work function) and
increases with a decrease in pressure, during pumpdown, to a
maximal peak rate, thereafter either diminishing to the
point at which the discharge extinguishes or gives way to
x-ray production (depending on the magnitude of the applied
potential);
larger area plates lower the field strength
values needed to elicit comparable PAGD production, displace
the PAGD region downward in the pressure scale and increase
the peak PAGD rate;
higher power supply capacitances slow down the
PAGD rate.
US Patent # 5,449,989
US Cl. 318/558 ~ September 12, 1995
Energy Conversion System
Paulo N. Correa & Alexandra N. Correa
Abstract ~
An energy conversion device includes a
discharge tube which is operated in a pulsed abnormal glow
discharge regime in a double ported circuit. A direct
current source connected to an input port provides
electrical energy to initiate emission pulses, and a current
sink in the form of an electrical energy storage or
utilization device connected to the output port captures at
least a substantial proportion of energy released by
collapse of the emission pulses.
Current U.S. Class: 318/558; 313/581;
315/111.21; 315/111.31; 315/171; 315/173; 327/533; 327/601
Intern'l Class: H03K 003/37
Field of Search: 318/558,727 313/306,581
315/84.51,111.01,111.21,111.31,160,171,173,187,188,193,200
R,207
328/59,60,61,69,70,85,208,219,220,225,249,250,251,260,264
363/116,117
References Cited ~
U.S. Patent Documents:
3,205,162 ~ Sep., 1965 ~ MacLean.
3,471,316 ~ Oct., 1969 ~ Manuel.
3,705,329 ~ Dec., 1972 ~ Vogeli.
3,801,202 ~ Apr., 1974 ~ Breaux.
3,864,640 ~ Feb., 1975 ~ Bennett.
3,878,429 ~ Apr., 1975 ~ Iwata.
4,009,416 ~ Feb., 1977 ~ Lowther.
4,128,788 ~ Dec., 1978 ~ Lowther.
4,194,239 ~ Mar., 1980 ~ Jayaram, et al.
4,443,739 ~ Apr., 1984 ~ Woldring.
4,489,269 ~ Dec., 1984 ~ Edling, et al.
4,527,044 ~ Jul., 1985 ~ Bruel, et al.
4,772,816 ~ Sep., 1988 ~ Spence
4,896,076 ~ Jan., 1990 ~ Hunter, et al.
5,126,638 ~ Jun., 1992 ~ Dethlefsen.
Other References:
Tanberg, R. "On the Cathode of an Arc Drawn in Vacuum",
(1930), Phys. Rev., 35:1080.
Kobel, E. "Pressure & High Vapour Jets at the Cathodes
of a Mercury Vacuum Arc", (1930), Phys. Rev., 36:1636.
Aspden, H. (1969) "The Law of Electrodynamics", J. Franklin
Inst., 287:179.
Aspden, H. (1983) "Planar Boundaries of the Space-Time
Lattice" Lettere Al Nuovo Cimento, vol. 38, No. 7, pp.
243-246.
Aspden, H. (1980) "Physics Unified", Sabberton Publications,
pp. 14-17, 42-45, 88-89, 190-193.
Pappas, P. T. (1983) "The Original Ampere Force and
Bio-Savart & Lorentz Forces", Il Nuovo Cimento, 76B:189.
Graham, G. M. & Lahoz, D. G. (1980) "Observation of
Static Electromagnetic Angular Momentum in Vacuo", Nature,
vol. 285, pp. 154 & 155.
Sethlan, J. D. et al., "Anomalous Electron-Ion Energy
Transfer in a Relativistic-Electron-Beam-Plasma" Phys. Rev.
Letters, vol. 40, No. 7, pp. 451-454 (1978).
Description ~
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to energy conversion
circuits utilizing discharge tubes operating in the pulsed
abnormal glow discharge (PAGD) regime.
2. Review of the Art
Such discharge tubes and circuits
incorporating them are described in our copending U.S.
patent application Ser. Nos. 07/922,863 and 07/961,531. The
first of these applications discloses discharge tube
constructions particularly suited for PAGD operation, and
the second discloses certain practical applications of such
tubes, particularly in electric motor control circuits. The
review of the art contained in those applications is
incorporated herein by reference, as is their disclosure and
drawings.
It is known that there are anomalous cathode
reaction forces associated with the cathodic emissions
responsible for vacuum arc discharges, the origin and
explanation of which have been the subject of extensive
discussion in scientific literature, being related as it is
to ongoing discussion of the relative merits of the laws of
electrodynamics as variedly formulated by Ampere,
Biot-Savart and Lorentz. Examples of literature on the
subject are referenced later in this application.
SUMMARY OF THE INVENTION
The particular conditions which prevail in a
discharge tube operated in the PAGD regime, in which a
plasma eruption from the cathode is self-limiting and
collapses before completion of a plasma channel to the anode
gives rise to transient conditions which favour the
exploitation of anomalous cathode reaction forces.
We have found that apparatus utilizing
discharge tubes operated in a self-sustaining pulsed
abnormal glow discharge regime, in a double ported circuit
designed so that energy input to the tube utilized to
initiate a glow discharge pulse is handled by an input
circuit substantially separate from an output circuit
receiving energy from the tube during collapse of a pulse,
provides valuable energy conversion capabilities.
The invention extends to a method of energy
conversion, comprising initiating plasma eruptions from the
cathode of a discharge tube operating in a pulsed abnormal
glow discharge regime utilizing electrical energy from a
source in a first circuit connected to said discharge tube,
and capturing electrical energy generated by the collapse of
such eruptions in a second circuit connected to said
discharge tube.
SHORT DESCRIPTION OF THE DRAWINGS
The invention is described further with
reference to the accompanying drawings, in which:
[ Figures open on a new page ]
FIG. 1
shows variation of applied DC current and pulse AC rms
currents characteristic of a low current PAGD regime, as a
function of decreasing pressure, for a 128 cm.sup.2 H34
aluminum plate pulse generator having a 5.5 cm gap length
and being operated in the single or plate diode
configuration of FIG. 11A, at .sup..about. 600 VDC.
FIG. 2
shows variation of applied DC current and AC rms currents of
a high current PAGD regime, as a function of the decreasing
pressure, for a device identical to that of FIG. 1, and
operated at the same potential.
FIG. 3
shows PAGD rate vs. pulse generator cathode temperature as a
function of the time of continuous PAGD operation, for a
pulse generator with 64 cm.sup.2 plates having a 4 cm gap
distance, operated at VDC = 555 (av) and R1 = 600 ohms (see
FIG. 9).
FIG. 4
shows PAGD frequency variation with time, for 18 successive
spaced one-minute PAGD runs for a pulse generator with 128
cm.sup.2 plates, and a 5.5 cm gap distance, operated at
VDC=560 (av) and R1 = 300 ohms.
FIG. 5
shows variation of the PAGD frequency in pulses per minute
(PPM) with increasing charge of a PAGD recovery charge pack
(see FIG. 9), as measured in terms of the open circuit
voltage following 15 minutes of relaxation after each one
minute long PAGD run, repeated 18 times in tandem, under
similar conditions to FIG. 4.
FIG. 6
shows volt amplitude variation of continuous PAGD at low
applied current, as a function of decreasing air pressure,
for a 128 cm.sup.2 plate area device, gap length=5 cm; (DCV
at breakdown = 860).
FIG. 7
shows volt amplitude variation of continuous PAGD at high
applied current as a function of the decreasing air
pressure, for a 128 cm.sup.2 plate area device, gap length=5
cm; (DCV at breakdown = 860).
FIG. 8
is a schematic diagram of a first experimental diode
(without C6) or triode PAGD circuit.
FIG. 9
is a schematic diagram of a preferred diode or triode PAGD
circuit in accordance with the invention.
FIGS.
10A, 10B and 10C are
fragmentary schematic diagrams showing variations in the
configuration of the circuit of FIG. 9.
FIG.
11 is a modification of FIG. 9, in which an
electromagnetic machine, in the form of an electric motor,
is connected into the circuit as an accessory
electromechanical arm.
FIG.
12 shows a further development of the circuit of
FIG. 9, permitting interchange of driver pack and charge
pack functions.
FIG.
13 shows open circuit voltage relaxation curves
for battery packs employed in tests of the invention,
respectively after pre-PAGD resistive discharge (DPT1 and
CPT1), after a PAGD run (DPT2 and CPT2) and after post-PAGD
resistive discharge (DPT3 and CPT3).
FIG.
14 shows an example of negligible actual power
measurements taken immediately before or after a PAGD run,
showing both the drive pack loss and the charge pack gain in
DC Watts; DP resistance = 2083 ohms; CP resistance = 833
ohms.
FIGS.
15A and 15B
show resistive voltage discharge curves for two separate
lead-zero gel-cell packs utilized respectively as the drive
and the charge packs; load resistances employed were 2083
ohms across the drive pack (FIG. 15A) and 833 ohms across
the charge pack (FIG. 15B).
FIG.
16 shows resistive discharge slopes for a drive
pack before and after a very small expenditure of power in
providing energy input to a PAGD run; R = 2083 ohms.
FIG.
17 shows resistive discharge slopes for a charge
pack before and after capturing energy from the collapse of
PAGD pulses in the same test as FIG. 15; R = 833 ohms.
FIG.
18 shows resistive discharge slopes for a drive
pack before and after a very small expenditure of power in
providing energy input to a PAGD run in a further
experiment; R = 2083 ohms.
FIG.
19 shows resistive discharge slopes for a charge
pack before and after capturing energy from the PAGD run of
FIG. 18; R = 833 ohms.
FIG.
20 shows an example of operational measurements
taken videographically during a 10 second period for both
the power consumption of the drive pack (PAGD input) and the
power production captured by the charge pack (PAGD output);
the two values are also related by the expression of percent
breakeven efficiency.
FIG.
21 shows variation of PAGD loaded voltage of a
drive pack (in squares) compared with the PAGD charging
voltage of the charge pack (in circles), during more than 1
hour of continuous PAGD operation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The basic PAGD function and the construction
of discharge tubes specifically designed for PAGD operation
are described in our corresponding copending applications
Nos. 07/922,863 (the '863 application) and 07/961,531 (the
'531 application). For purposes of the experiments described
below four aluminum H34 plate devices (one with 64 and three
with 128 cm.sup.2 plate areas) and three aluminum (H200)
plate devices (one with 64 and two with 128 cm.sup.2 plate
areas), with interelectrode gap lengths of 3 to 5.5 cm, were
utilized at the indicated vacua, under pumpdown conditions
and with either air or argon (ultra high purity,
spectroscopic grade 99.9996% pure) constituting the residual
gas mixture. The pumpdown conditions were as described in
the '863 application. Some experiments were performed with
the tubes under active evacuation, at steady-state
conditions, while others utilized sealed devices enclosing
the desired residual gas pressures.
The circuit designs utilized in the various
experiments to be described are set out further below, and
represent further developments and extensions of the
circuits set forth in the '531 application.
Test equipment utilized was as follows:
An Edwards (trade mark) thermocouple gauge
(TC-7) was employed for the determination of pressure down
to 1 micron of mercury (0.001 Torr).
Banks of Beckman (trade mark) rms multimeters
225 and 330 (30 and 100 kHz bandwidths, respectively) were
utilized for all current measurements.
Frequency meters capable of discriminating
events up to 0.1 nanosecond apart, and having adjustable
amplitude windows, were used. Direct analysis on a Tektronix
(trade mark) dual-trace, storage scope (Model 549) was also
carried out for both parameters.
Split-phase, single-phase and two-phase motors
were employed, of the synchronous, induction and universal
types, as previously described in the '531 application, in
the accessory electromechanical arm that may be coupled to
the power producing circuit described in the present
application.
Large banks of 12 V, 6 Ah lead-acid gel cells
(Sonnenschein (trade mark) A212/6S) were utilized either as
power sources (designated as drive packs) or as accumulators
of the energy (referred to as charge packs) captured by the
test circuits. Charge packs made of rechargeable 9 V NiCad
or of nominally nonrechargeable C-Zn or alkaline batteries
were also utilized.
PAGD emission areas were determined by
metallographic examination of a series of craters produced
by PAGDs in clean H34 cathodes, under a metallurgical Zeiss
(trade mark) standard 18 microscope equipped with an
epi-fluorescent condenser, very high power apochromatic
objectives and a 100 W mercury lamp. For best results a
focusable oblique source of light (12 V halogen) was also
added to the incident light.
Following our low and high applied current
studies on PAGD production as set forth in the '863
application, we noticed that the AC rms value of the
component associated with each abnormal glow discharge pulse
varied nonlinearly with the magnitude of the applied
current. We originally noted the existence of a current
induced shift of the entire PAGD region upward in the
pressure scale: while the PAGD regime became more clearly
defined as the applied constant DC was increased, the
pressure required to observe the PAGD increased two to three
orders of magnitude. In the course of these rarefaction
studies we found that, at applied currents of 1 mA or less,
the rms value of the different AC waveforms associated with
the consecutive regimes of the discharge
(TRD.fwdarw.NGD.fwdarw.AGD+PAGD) was, by more than half log,
inferior to the value of the applied DC current, during the
first two regimes (TRD and NGD) and reached a value
equivalent to the applied current with the onset of
spontaneous PAGD, at pressures <0.1 Torr (see FIG. 1);
however, in the downward tail of the PAGD regime (down to
3*10-3 Torr), the AC rms current component of each PAGD
again decreased to more than half log of the intensity of
the applied DC value, in a manner proportional to the log of
the decreasing pressure. In stark contrast, at high applied
currents of .sup..about. 500 mA, and aside from the high
current-induced upward shift in pressure of the PAGD regime
(to the point that the compression of the previous regimes
on the pressure scale results in their suppressing, as was
the case in the present example), the AC rms component
associated with each pulse (see closed circles, FIG. 2) is,
from onset of the discharge at .sup..about. 8 Torr, greater
in magnitude than the value of the applied current (open
circles, FIG. 2). Under the conditions described, the
distribution of the field current associated with each
pulsed abnormal glow discharge approached (on a linear Y
axis; not shown) an unimodal gaussian distribution with the
pressure peak at .sup..about. 1 Torr, and a corresponding
observed maximum of 7.5.times. higher AC rms values than the
applied DC values.
We have previously described in the '863
application how the PAGD frequency is affected by several
factors, namely: the magnitude of the parallel discharge
capacitance, the value of the negative pressure for the
relevant vacuum PAGD range, the magnitude of the applied
potential, the magnitude of the applied direct current, the
interelectrode gap distance and the area of the parallel
plate electrodes. In the '531 application we have also
described how the wiring configuration (plate diode versus
triode) affects the PAGD frequency by adding tungsten
autoelectronic emissions from the axial electrode, to those
emissions from the plate. There are other factors which
limit the PAGD regime of discharge and have also been
discussed in the '863 application. The following data
indicates their specific effect upon PAGD frequency.
In the data presented in Table 1, control of
the frequency parameter for the circuit shown in FIG. 9 is
by a ballast resistance R1 within a specific range of
interest (.sup..about. 800-150 ohms, for Table 1
experimental conditions), and this in turn increases the
applied current which, at "high current" values (i.e.
>100 mA, as for Table 1 conditions), will drive the PAGD
frequency up, as previously reported in the '863
application.
Table 2 shows the effect of the progressive
displacement of a given frequency, chosen as 200 PPS, with
the cumulative pulse count of the same device, in the plate
diode configuration. This displacement of the same frequency
(cf. group #'s 1-3, Table 2) onto higher pressure regions is
shown to be promoted by the alteration of the work function
of the PAGD emitting cathode, such as this is caused by the
cumulative pulse count and resultant crater formation on the
electrode surface. After the first million pulses, the anode
facing cathode surface is completely turned over by emission
sites, and this corresponds well to the threshold crossed by
group #2, Table 2. Once the cathode surfaces are broken in,
the rates shown in groups #3 and 4, Table 2, tend to remain
constant. Originally we wondered whether this might be
caused by the alteration of the electrostatic profile of the
plasma sheaths at the periphery of the envelope, due to the
mirroring deposits that result from the sputter of ions and
trapped neutral atoms (from air gases or metallic vapor)
associated with the autoelectronic emission mechanism (and
from further emissions triggered in turn, by secondary ionic
bombardment of the cathode with molecular species present in
the plasma ball formed over the primary emission site).
However, reversal of the plate polarity (firing the ex-anode
as a crater-free cathode) for over a million counts,
followed by re-reversal to the original polarity, the entire
operation being performed in air as the residual gas
substrate, led to the partial recovery of the original work
function for as long as the test was run (1.5*10.sup.4
pulses), as shown by a comparison of groups #2,4 and 5,
Table 2. From a metallographic examination of the surfaces
of plates used solely as anodes, we have also concluded that
prolonged PAGD operation has the effect, not only of
cleaning the anode surface from surface films and adsorbed
gases, as ionic bombardment promoted by electromagnetic
induction coils does, but it also does more--it polishes the
target surface and smooths it by a molecular erosive action.
Observations of the surface of reversed cathodes, shows the
same smoothing and polishing effects observed in exclusive
anodes. Thus the recovery of the PAGD rates promoted by
polarity reversal of the plates is not a function of the
sputter-promoted mirroring deposits on the envelope wall,
but a function of the actual work-function of the emitting
cathode.
Another variable that interacts with the PAGD
frequency is the molecular nature of the residual gas: Table
3 shows the differential frequency response of air with a
halogen quencher, argon, for the same pulse generator
employed in the tests of Table 2. It is apparent that argon
obtains much higher rates of AGD pulsation for the same
range of negative pressure, for the same "broken in"
cathode, than does the air mixture. All these measurements
were taken at cathode support-stem temperatures of
35.degree. C.
Time of operation is also a variable affecting
the frequency and operating characteristics of the cathode,
as it becomes expressed by the passive heating of the
cathode, an effect which is all the more pronounced at the
higher pressures and at the higher frequencies examined.
Utilizing the triode circuit discussed in the next section,
the pulse rate of a PAGD generator with 64 cm.sup.2 plates
can be seen (see FIG. 3) to decrease, at a negative pressure
of 0.8 Torr, from 41 PPS to the operating plateau of 6 PPS
within 15 minutes of continuous operation, as the
temperature of the cathode support increased from 19.degree.
to .sup..about. 44.degree. C. As the temperature plateaus at
.sup..about. 51.degree..+-.1.degree. C., so does the pulse
rate at 6 PPS, for the remaining 48 minutes of continuous
operation.
However, in order to confirm this
time-dependent heating effect and threshold, we also
performed the same experiment, utilizing the same circuit
and the same negative air pressure, with twice as large a
cathode area (128 cm.sup.2, which should take nearly twice
as long to heat), being operated for 18 one-minute long
continuous periods equally spaced apart by 15 minutes of
passive cooling, with the cathode stem always at
19.7.degree. to 21.degree. C., room temperature at the start
of each period. The results surprised us, inasmuch as they
showed that for a larger area tube which takes longer to
heat to the same temperatures at comparable rates of PAGD
triggering, one could observe a much earlier frequency
reduction (by half, within the first 5 minutes or periods of
interrupted functioning) in the absence of any significant
heating effect (<1.5.degree. C.) of the cathode (see FIG.
4). Repetition of these experiments has led us to conclude
that, as shown in FIG. 5, the variable responsible for this
repeatedly observed reduction in the PAGD frequency, when
the PAGD operation sequence is systematically interrupted,
is the state of charge/discharge of the battery pack (the
charge pack) at the output of the triode circuit in
question: the PPM rates in FIG. 5 decrease rapidly with the
steepest rate of charging of the charge pack and the fastest
recovery rate of its open circuit voltage; above a given
state of charge, when the open voltage of the charge pack
climbs more slowly (>340 V), in a log fashion, the PPM
rate stabilizes at its plateau values.
Confirmation of the importance of the charge
pack in the PAGD function of the present circuitry here
considered, comes from the fact that the size (the number of
cells) and the intrinsic capacitance of the charge pack
affect the PAGD frequency dramatically (see Table 4):
increasing the charge pack size of 29 cells to 31, by 7%
leads to a 10-fold reduction in frequency; further increases
in the number of charge pack cells extinguishes the
phenomenon. On the upper end of the scale, this effect
appears to be tied in to restrictions that it places on the
ability of the larger charge packs to accept the discharge
power output once the charge pack voltage exceeds the PAGD
amplitude potential. All of these measurements were
conducted with the same 128 cm.sup.2 plate PAGD generator,
at a pressure of 0.8 Torr and in the triode configuration
(see FIG. 9).
Other factors can also affect the frequency:
the motion of external permanent magnetic fields oriented
longitudinally with the interelectrode gap, external pulsed
or alternating magnetic fields, external electrostatic or
electromagnetic fields, specific connections of the earth
ground, and the presence of a parallel capacitative,
capacitative-inductive or self-inductive arm in the circuit,
such as we have described for our electromechanical PAGD
transduction method as described in the '531 application.
Analysis of the modulation of PAGD amplitude
is simpler than that of its frequency, because fewer factors
affect this parameter: (1) magnitude of the applied
potential, (2) interelectrode gap distance and (3) the
negative pressure, as shown in the '863 application, for
"low" applied currents. As the magnitude of the applied
potential itself is limited by the gap and the pressure, to
the desired conditions of breakdown, the important control
parameter for the PAGD amplitude is the pressure factor.
This is shown in FIGS. 6 and. 7, respectively for "low" (5
mA) and "high" (.sup..about. 500 mA) applied currents and
for the same plate diode configuration of a H34 Al 128
cm.sup.2 plate PAGD generator (5 cm gap), in the simple
circuit described in the '863 application; it is apparent
that both positive and negative components of the amplitude
of these pulses in the oscillograph, are a function of the
pressure, but the maximum cut-off limit of our equipment,
for the negative component (at 240 volts for the "low"
current experiment and at 120 volts for the "high" current),
precluded us from measuring the peak negative voltage of
these pulses. However, rms measurements of the pulse
amplitude at the plates and DC measurements at the circuit
output to the charge pack indicate that the negative
component increases with decreasing pressure to a maximum,
for a given arrangement of potential and gap distance; no
pressure-dependent bell shape variation of the pulse
amplitude, as that seen for the positive component at "high"
applied currents (FIG. 7) is observed with the negative
amplitude component. For the typical range of 0.8 to 0.5
Torr, the rms value for pulse amplitude varies from 320 to
480 volts, for a 5.5 cm gap distance and applied DC voltages
of 540 to 580. PAGD amplitude is a critical factor for the
design of the proper size of the charge pack to be utilized
in the optimal circuit.
The development of the circuits to be
described stemmed from fundamental alterations to the
principles implicit in our previous methods of
electromechanical transduction of AGD plasma pulses as
described in the '531 application. Whereas this
electromechanical coupling (capacitative and
self-inductive), utilized directly, energizes the AGD pulses
inverted from the DC input by the vacuum generator, the
purpose of the development that led to the presently
described experiments was to capture efficiently, in the
simplest of ways, most of the pulse energy in a closed
circuit, so that power measurements for the energy
transduction efficiency of the observed endogenous pulsation
could be carried out. Ideally, comparative DC power
measurements would be performed at both the input and output
of the system, taking into account the losses generated
across the components; this would obviate the measurement
problems posed by the myriad of transformations implicit in
the variable frequency, amplitude, crest factor and
duty-cycle values of the PAGD regime, and necessitated some
form of rectification of the inverted tube output. From the
start our objective was to do so as simply as possible.
Early circuits utilizing half-wave rectification methods
coupled in series to a capacitative arm (for DC isolation of
the two battery packs), with the charge pack also placed in
series, showed marginal recoveries of the energy spent at
the PAGD generator input. Attempts at inserting a polar
full-wave rectification bridge led, as shown in FIG. 8, to
the splitting of the capacitor into capacitors C3 and C5, at
the rectification bridge input, and capacitor C4 in series
with both capacitors, all three being in a series string in
parallel with the PAGD generator. Under these conditions a
DC motor/generator could be run continuously in the same
direction at the transversal output (U1 and U2) of the
bridge; but if this inductive load was replaced with a
battery pack CP (charge recovery pack), either the parallel
capacitor C4 had to remain in the circuit, for the diode
configuration or, less desirably, a further capacitor C6
could replace C4 and connect one electrode, preferably the
cathode C, to the axial member of the discharge tube T, thus
resulting in a first triode configuration as actually shown
in FIG. 8. Energy recovery efficiencies of the order of 15
to 60% were obtained utilizing C6 in this manner, but
measurements of the potential and currents present at the
output from the rectifier bridge were substantially lower
than those obtained using optimal values of C4. Effectively,
under these conditions, much of the power output from the
tube was never captured by the output circuit formed by the
second, right hand arm of the system and, being prevented
from returning as counter-currents to the drive pack DP by
diodes D1 and D4, was dissipated and absorbed by the
interelectrode plasma, electrode heating and parasitic
oscillations.
Solutions to this problem were explored using
the circuit shown in FIG. 9, which still maintains the
necessary communication link for the quasi-sinusoidal
oscillation of the capacitatively stored charges at the
input and outputs of the rectification bridge, but
integrated the functions of capacitor C4 into the single
rectification circuit, in the form of an asymmetric
capacitative bridge C7a and C7b placed transversally to the
capacitative bridge formed by C3 and C5 and in parallel with
the charge pack CP at the output from the rectification
bridge D5, D6, D2, D3. This second capacitative bridge is so
disposed as to have its centre point connected to the anode
A through capacitor C5. If the axial member of the Tube T
were to connect to the junction of D2 and D3 instead of at
the junction D5-D6, the function of bridge C7a and C7b would
be connected to the cathode C through capacitor C3. The
capacitative bridge is insulated from the charge pack whose
voltage it stabilizes, by rectifiers D7 and D8, which also
prevent leakage of charge across C7a and C7b. The anode and
cathode oscillations generated by the electrostatic charge
transduction through C3 and C5 into the poles of the charge
pack are trapped by the transversal transduction of the C7
bridge, at the outputs from the rectification bridge, of
which the oscillation has to become split between the bridge
inputs into half-waves, for electrostatic transduction and
full wave rectification to occur. In fact, under these
conditions, removal of the C7 bridge will suppress the PAGD
phenomenon, unless other circuit variables are also altered.
The transversal bridge is thus an essential piece of this
novel circuit. Variations in the circuit as shown in FIG. 10
were then studied, the first two being selectable utilizing
switch S2 (FIG. 9).
The presence of the capacitative bridge
effectively reduces the dynamic impedance of the charge pack
CP so that the output circuit approximates to a
characteristic in which it presents a very high impedance to
the tube T at potentials below a certain level, and a very
low impedance at potentials above that level.
With this modified circuit, more effective
recovery of the energy produced by collapse of the PAGD
pulses is possible, with more effective isolation from the
input circuit utilized to trigger the pulses. Under these
conditions, the energy captured by this circuit at the
output, is not directly related to that utilized in
triggering the pulses from the input. The attainment of this
condition critically depends on the large capacitance of the
transversal bridge being able to transfer the output energy
from the tube T into the charge pack CP. Under these
conditions, we have found, as will be shown below, that the
large peak pulse currents released by collapse of the PAGD
pulses released more energy than is used to trigger them,
and these findings appeared to tally with other observations
(abnormal volt-ampere characteristics and anomalous pulse
currents, etc.) associated with the anomalous cathode
reaction forces that accompany the auto-electronic
emission-triggered PAGD regime. Experiments so far indicate
that the power output can be increased proportionately to
the series value of C3, C5 and the two identical C7
capacitors.
The circuit of FIG. 10 can be integrated with
a circuit such as that disclosed in the '863 application as
shown in FIG. 11, in which a part of the energy recovered
can be shunted by the switch S4 into an induction motor M1
having rotor R, to a degree determined by the adjustment of
potentiometer R4 and the value selected for C4.
The circuit of FIG. 11 can be further
developed as exemplified in FIG. 12 to include
configurations which provide switching permitting
interchange of the functions of charge packs and the drive
packs, it being borne in mind that the nominal potential of
the drive pack must be substantially higher than that of the
charge pack, the former needing to exceed the breakdown
potential of the tube at the beginning of a PAGD cycle, and
the latter to be less than the extinction potential.
FIG. 12 essentially represents a duplication
of the circuit of FIG. 11, the two circuits however sharing
two identical battery packs BP1 and BP2, and being provided
with a six pole two way switch, the contact sets of which
are identified as S1, S2, S3, S4, S5 and S6. When the
contacts are in position A as shown, battery pack BP1 acts
as a drive pack for both circuits, with the upper half (as
shown) of the battery pack BP2 forming the charge pack for
the upper circuit, and the lower half forming the charge
pack for the lower circuit. When the pack BP1 is at least
partially discharged, the switch is thrown so that contacts
move to position B, which reverses the function of the
battery packs thus allowing extended operation of the motors
in each circuit each time the switch is thrown.
Based on the manufacturer's data, and using
current values within the range of our experimentation as
discussed in the next sections, an optimal discharge cycle
for a fully charged 6.0 Ahr battery pack at 0.300 A draw is
20 hours, as claimed by the manufacturer, and this
corresponds to a cycling between 100% (12.83 V/cell open
circuit and load start voltage) and <1% (10.3 V/cell load
voltage) of the battery's absolute charge capacity. Even
though the discharge mechanism is a time cumulative process
with a log function, the discharge can, within 4 to 5 hour
time segments (or periods with 20-25% of the full range), be
regarded as practically linear with time. This trait, or
linearization of the discharge slope, becomes more marked
with advancing age and decreasing absolute storage capacity
of the cells.
The proportionality between open circuit
voltage and the percentage of residual relative capacity for
these cells when new (uncycled and not yet aged) is uniform
over 98% of the permissible charge capacity withdrawal; in
practice this translates into a slope that becomes steeper
with time, while the absolute storage capacity diminishes.
In turn, this decreasing absolute capacity of the cells
results in shorter load discharge times and their further
linearization.
A circuit in .general accordance with FIG. 9,
employed in the studies reported in this and the following
sections, utilizes a drive pack of 46*12 V Lead acid
gel-cells each with a 6.0 Ah rating, and a charge pack with
28 or 29*12 V identical cells. The charge pack was cycled
anywhere from 11.2 V to 12.8 V/cell (open circuit voltages),
within the proportional region of the relative capacity
slope, to yield a capacity increment in the order of 50%
(e.g. from 20 to 70%), anywhere within the range of 2 to
100% of its total charge capacity, assumed for now as
invariant. The charging process, hereinafter referred to as
a PAGD run, took about 20-30 minutes under optimal
conditions. The drive pack typically consumed, in the same
period of time, 4 to 11% of its initial total capacity , its
open circuit voltage typically falling 0.1 to 0.2 V per cell
after a PAGD run, within the open circuit range of 12.8
V/cell (100% relative capacity) and 11.2 V/cell
(.sup..about. 2%). At the 100% capacity benchmark, the drive
pack would theoretically have 20 h*46 cells*12.83 V/cell*0.3
A=3.5 KWh, and the charge pack, for example, 20 h*29*12.83
V/cell*0.3 A=2.2 KWh. Since the capacity per cell is linear
with the open circuit voltage within the proportional range,
as claimed by the manufacturer, we projected the open
circuit voltage intercepts on the manufacturer's
proportional curve in order to determine the residual
percentage of the total relative capacity and the standard
hours of operation left, from any experimental open circuit
voltage measurements.
Three pulse generators (2*128 cm.sup.2 and
1*64 cm.sup.2 plate areas) were employed in these studies;
they were operated in PAGD runs at 1-120 pulse/second rates,
within a negative pressure range of 0.2 to 0.8 Torr and with
applied direct currents of 0.2 to 0.6 A.
Both drive and charge packs utilized cells
which were bought new at the same time and had initial
charge values of 12.4 to 12.55 V/cell (open circuit). These
batteries are capable of energy densities of 33-35 Whr/kg.
However, the experiments shown in Table 5 are selected from
a series that spanned nearly 12 months, beginning 6 months
after purchase; hence, loss of absolute storage capacity by
the batteries had occurred in the intervening time, as a
function of both age and charge/discharge cycle life.
Measurements of the open voltage of either
drive (D) or charge (C) (see column 2, Table 5) packs for 8
separate experiments, all utilizing the triode
configuration, were performed before (b) and after (a) a
PAGD run (see columns 3 and 4), at either 15 or 30 minutes
(see column 26) of the open circuit voltage relaxation after
a PAGD run was terminated. Corresponding open circuit
voltages per cell are shown in column 5, and the percentages
of the predicted total relative charge capacity resulting
from the intercepts on the manufacturer's proportional curve
are shown in column 6, Table 5. Equivalent maxima for the
theoretical hours of operation left are shown in column 7,
the percentage change in relative capacity arising as a
consequence of either charge pack charge capture (capacity
gained) or of drive pack output (capacity lost) is shown in
column 8. Translating the intercepts into power units yields
the values shown in column 9, Table 5, for total kWh left in
each pack before and after PAGD production, those shown in
column 10 for the actual power gained and lost during the
periods of operation (presented in column 12) and those
shown in column 13 for the power predicted to be gained or
lost per hour of PAGD production. On the basis of the
experimental open voltage values and their intercepts, the
predicted net kWh values per hour of PAGD energy production
(after deduction of measured losses) and the corresponding
experimental breakeven efficiencies (where breakeven=100%)
are presented, respectively, in columns 14 and 15. The PAGD
frequency per second is shown in column 11; the number of 12
V cells, in column 16; the tube ID, in column 17; the
cathode (and anode) area (s), in column 18; the plate
material, in column 19; the input ballast utilized (R1, FIG.
9), in column 20; the size of each capacitor (C3 or C5) of
the tube output bridge, in column 21; the size of each
capacitor (C7a or C7b) of the transversal capacitative
bridge, in column 22; the status of S4 and thus, of the
parallel and auxiliary electromechanical arm (see FIG. 11),
in column 23; the negative air pressure in column 24; the
gap distance between the plates, in column 25; and columns
27,28 and 29, show the status of the elements of the
switched on parallel electromechanical arm of the
circuit--the parallel C4 capacitor, the motor input resistor
R4 and the motor revolutions per minute (measured
stroboscopically), respectively.
From these figures of Table 5, and utilizing
the data for the two first examples shown, we calculated the
predicted performance of the system based on the open
voltage measurements. In the first example, where the system
was run continuously without interruption, the charge pack
increased the percentage of its total capacity by 43% (a
two-fold increase in capacity) and, during the same period,
the driver pack decreased the percentage of its total
capacity by 7% (a .sup..about. 10% decrease in capacity
relative to the percentage of residual total capacity at the
start, i.e. 77%) (cp. columns 6 and 8, Table 5). Subtracting
the predicted initial total energy (0.835 KWh) available to
the charge pack before the experimental run (first line of
column 9, Table 5) from the predicted total energy (1.823
KWh, second line of column 9) available to the charge pack
after the PAGD charge run, gives us the total energy gained
by the charge pack: 0.988 KWh (column 10) in 21.5 minutes
(column 12) of continuous PAGD performance. Conversely,
subtracting the predicted final total energy (2.4 KWh)
available to the driver after the experimental run (fourth
line of column 9, Table 5) from the predicted total energy
(2.66 KWh, third line) available to the driver before the
PAGD charge run, gives us the total energy lost by the drive
pack: 0.26 KWh in 21.5 minutes. If we divide the total
available energy gained by the charge pack, by the total
energy lost by the drive pack, we obtain a surplus factor of
3.9.times., or 388% of the breakeven point (column 15). The
same values result from dividing the charge pack % of total
capacity gain by the drive pack % of total capacity lost,
and then downscaling this value by multiplying it by the
typical scale factor for the two packs, 29/46=0.63.times..
In an analogous fashion, we analyzed the
results for the second example shown in Table 5. Here, the
charger increased the percentage of its total capacity by
45.5% (a 22.75 fold increase in estimated total relative
capacity) and, during the same period, the driver decreased
the percentage of its predicted total capacity by 7% (a
.sup..about. 17.5% decrease in capacity relative to the
percentage of residual total capacity at the start, i.e.
40%). By dividing the predicted total available energy
gained by the charge pack (0.962 KWh/18 minutes) by the
expected total energy lost by the driver pack (0.246 Kwh/18
minutes) we obtain a surplus factor of 3.9.times., or 391%
of the breakeven point. This corresponds to an interrupted,
total sequential run of 18 minutes, each minute-long run
being separated by a cooling and voltage relaxation period
of 15 minutes before the next run is carried out, at an
average PAGD frequency of 61 PPS.
Analysis of the remaining results illustrates
how a number of PAGD controlling parameters interact to
determine conditions for effective maintenance of a PAGD
regime. The lower gain and higher loss per unit time
registered for the third run of Table 5, which results in
the lower breakeven efficiency of 230% and a smaller net
power production rate than before (power estimates of 1.396
kWh/h of PAGD operation vs 2.387 kWh/h, for the second run,
Table 5) illustrate, for example, the combined effect of
lowering the pressure (0.8 to 0.7 Torr) and running the PAGD
continuously (the heating effect), both of which depress the
PAGD frequency. The fourth run of Table 5 identifies the
continuous performance of a "broken in" softer grade of
aluminum (column 19), having a lower work-function (as
determined from the higher PAGD frequency spectrum) than the
harder H34 plates of the previous examples, and shows that,
despite the series value of the total capacitance being
higher (5,333 mfd vs 4,030 mfd for runs one through three),
and despite the higher vacuum (0.2 Torr), the lower
work-function results in a higher frequency; however, even
though this run registers a predicted higher breakeven
efficiency (310%) than the previous experiments, these
conditions result in a 4/5-fold lower estimate of net power
produced, when compared to the previous three PAGD runs.
PAGD runs 5 and 6, Table 5, illustrate the
effect of switching on the auxiliary electromechanical arm
of the circuit shown in FIG. 11. Increasing the amount of
charge capacitatively shunted into the electromechanical arm
by higher C4 values (column 27), and increasing the current
that feeds the squirrel cage induction motor utilized by
lowering R4 (column 28), results in a power capture by the
charge pack that registers an energy loss (predicted to be
96% efficient, falling short 4% of breakeven recovery), as
most of the tube output power is spent in the
electromechanical arm and its motor effect. Furthermore,
under the conditions of maximum electromechanical action,
the drain imposed on the drive pack becomes considerable
(see loss in columns 10 and 13), even if the C3 and C5
values are reduced, column 21, Table 5). These runs also
illustrate how the motor appears to function as an
electrical induction generator having rpm values much higher
than the synchronous values prescribed by the frequency of
the PAGD (column 29, Table 5).
The extremely large breakeven efficiency of
PAGD run 5, Table 5, indicates that with selected values of
C4 and R4, it is possible to operate the motor in the
auxiliary arm and still accumulate excess energy from the
PAGD production in the charge pack.
Runs 7 and 8 illustrate results obtained for
64 cm.sup.2 plates, and a shorter interelectrode gap
distance, for two pressures (0.8 and 0.5 Torr), the device
being open to a rotary pump manifold in the first instance
and sealed from the pump, in the second case. Despite the
lower vacuum, the higher pulse frequency (32 vs 5 PPS) and
breakeven efficiency (906% vs 289%) registered by run 8 when
compared to run 7, are a consequence of the method of run 8,
which was interrupted systematically by 5 passive cooling
periods, as in the case of run 2, whereas run 7 was
continuous. This again resulted in higher average PAGD
frequencies (at lower pressures), a predicted two-fold
greater gain and a predicted two-fold smaller loss (columns
13 and 14) for run 8.
FIG. 13 shows curves representing the slopes
of the open circuit relaxation voltages, which are linear
with the log of time elapsed from cessation of discharge,
for both drive and charge packs, in the same run 8 set out
in Table 5. The experiment in its entirety consisted of
preliminary resistor-loaded measurement discharges and their
corresponding open circuit voltages from the moment of
cessation of the resistive discharge (illustrated,
respectively, by the open squares of DPT1 for drive pack
relaxation time 1, and by the open circles of CPT1 for
charge pack relaxation time 1), followed by their relaxation
rates in the wake of the PAGD production (the hatched
squares of DPT2 for drive pack relaxation time 2, and the
hatched circles of CPT2 for charge pack relaxation time 2),
and finally, by the relaxation rates from the final
resistor-loaded measurement discharges (the black squares of
DPT3 for drive pack relaxation time 3, and the black circles
of CPT3 for charge pack relaxation time 3). Discharge
resistances were 833 ohms for the charge pack, and 2083 ohms
for the drive pack in all cases, corresponding to resistors
R3 and R2, respectively, of FIG. 9. This methodology will be
examined in greater detail below. It is apparent that, after
every load period, be this resistive (CPT1, DPT1, CPT3 and
DPT3) or due to PAGD operation (DPT2), the relaxation slope
is positive; as shown from slopes CPT1 and DPT1, the log
time proportionality of the open circuit voltage relaxation,
under these conditions, tends to plateau after .sup..about.
30 minutes. The exception to this general behaviour lies in
the voltage relaxation slope CPT2, which is negative and
reflects the charge accumulation occurring in the charge
pack and obtained by capture of energy produced during PAGD
operation, triggered by the energy drawn from the drive pack
during load time 2.
As a first approximation of electrical power
generated and consumed by the energy conversion system of
the invention, the previous open circuit voltage method is
of significance in showing the basic trends involved in
interaction of the operating parameters. However, in all
likelihood, it overestimates the actual values of electrical
power consumed and generated, for a variety of reasons.
First, it assumes that the relative capacity scale of the
batteries in the drive and charge packs is an absolute
charge capacity scale with an invariant maximal charge
retention, which it is not; in fact, the absolute charge
capacity is itself a variable subject to several factors,
such as the cycle life, overcharging or undercharged
conditions, cell age, residual memory and the rate of charge
and discharge. Hence, the inference of a uniform time scale
on the basis of the open circuit voltage/capacity intercepts
may not be warranted. Finally, it does not integrate the
open voltage decrease over time, and utilizes the
specification load current as the average current over time.
In order to obviate these problems, we
resorted to a variety of other measurement methods. First,
we proceeded to compare the closed circuit, preliminary,
resistive-load discharge measurements for either charge or
drive pack, under conditions of negligible loss of power, as
these measurements were statistical means (n=9) taken, at
equal intervals, during the first 90 seconds of the load
discharge, and obtained both just before the PAGD production
runs (but separated from each PAGD run by an open circuit
voltage relaxation of 30 minutes) and just after the runs
(but equally separated by a relaxation of 30 minutes). As an
example of the data generated by such an approach, FIG. 14
illustrates the shift of the slopes indicating marginal
power loss for the drive pack (from the closed squares to
the open squares) and those indicating gain of power for the
charge pack (from the open circles to the closed circles),
in actual total load power values.
Integration of these power measurements over
the projected load discharge time, taken from the family of
curves generated on the basis of the manufacturer's load
voltage over discharge time specifications, led to a direct
comparison of the new values, as shown in Table 6, with the
values presented in Table 5, for the first three instances
introduced. All values of Table 6 were obtained by resistive
measurements of power that entailed a negligible power loss.
Table 6 confirms the fundamental equivalence of runs 1
through 3, as already seen from their corresponding analysis
using the open voltage method (see runs 1 to 3, Table 5).
This new power estimation method also confirms the lower
loss encountered in run 2 utilizing interrupted PAGD
operation. While the breakeven efficiencies sensibly doubled
using this method, the estimates of actual electrical power
consumption recovery decreased by a 2 to 3-fold factor. Thus
this direct load voltage/amperage measurement method of
estimating actual power losses or gains, is a check upon the
open voltage method previously utilized.
Direct, instantaneous measurements of the
voltage and current characteristics of the PAGD production
and capture phenomena being discussed, were also performed
during PAGD runs for diverse sets of conditions, including
all those described in the two previous sections. In Table 7
we show these results for two PAGD generators having an
identical electrode area (128 cm.sup.2) and connected to
electrical energy capture circuits of three separate
configurations as set forth in FIGS. 10A, 10B and 10C and
column 2, Table 7. In the configuration of FIG. 10C, or
double diode configuration, both electrode plates act as
cathodes and the axial member as the anode collector
(experiments 1-4, for the H220 device and 13-14, Table 7,
for the H34 device). In the configuration of FIG. 10B, or
triode configuration, one plate acts as the cathode, the
axial member as an auxiliary cathode and the other plate as
a collector (experiments 5-9, Table 7). In the configuration
of FIG. 10A or single (plate to plate) diode configuration,
the axial member is disconnected, and the polarity of the
plates remain as in the triode configuration (experiments
10-12). All measurements were taken after 1 minute of PAGD
operation of the devices, which were, at the start of each
run, at room temperature. All cathodes had been previously
broken in with >2*10.sup.6 AGD pulses. The open circuit
voltage of the charge pack was, for all cases, at 359 to 365
volts, before each test. The direct measurements of the PAGD
input and output DC voltages and currents were obtained as
statistical means of 10 second long measurements, and at no
time did the standard error of the plate voltage mean exceed
35 volts.
The air pressure within the tube during these
tests is shown in column 3, Table 7, the drive pack DC
voltage (X), in column 5, the DC voltage across the plates
(Y), in column 6, the drive pack output current (PAGD input
current), in column 7, and the drive pack total watts output
is shown in column 8. Columns 9 and 10 show the PAGD voltage
(PAGD V=(X-Y)/I.sub.av) and the value of the PAGD extinction
potential in V/cm. The recovery co-ordinates (ie the PAGD
output energy) found at the U1-U2 output (FIG. 9), are shown
in columns 11 to 13, as the charge pack's E1-E2 input DC
voltage, amperage and power watts, respectively. The
calculated resistance of the entire circuit is given in
column 14, the registered PAGD frequencies in column 16, and
running conditions in columns 17 to 18. The breakeven
efficiency obtained by direct comparison of the electrical
power figures for the drive and charge packs, respectively,
is given in column 15. This assumes, for purposes of a
generalization of power production rates over time, that the
quasi-instantaneous, direct measurements here obtained can
be translated to outputs obtained per unit time, and thus
into direct Watt-hour measurements.
Data from runs 1 through 4 demonstrate that,
at these PAGD frequencies, there is no difference between
using fast switching (32 nanoseconds) MUR 860 diodes, or
regular 40HFR-120 silicon diodes, in the rectification
bridge of the electrical energy capture circuit, and that
the PAGD frequency varies as a function of decreasing air
pressure.
Runs 5 to 14 show that, in general, for the
same tube, the single and double diode configurations are
the most efficient, for the same pressure, the diode
configuration typically yields .about.1.5-2x larger
breakeven efficiencies (cp runs 10-11 and 13-14, with runs
5-9, Table 7). The largest accumulations of power are also
registered in the diode mode(s). This trend appears to be a
function of the much lower cathodic work-function of the
aluminum plates, than of the tungsten of the axial member
utilized as an auxiliary cathode in the triode
configuration. A feature of the data from these 14 different
runs is the consistent excess power outputs (column 15,
Table 7) and their narrower range (218 to 563%), when
compared to those observed with the previous two methods of
experimental analysis.
Run 12, Table 7, shows that the switching on
of the electromechanical arm can be performed without
entailing a power loss in the PAGD capture circuit, as
previously found for run 5, Table 5, utilizing the open
circuit voltage method. In fact, with C4=8 .mu.F and R4=500
ohms, the AC induction motor behaves as an electrical
flywheel (eg. 2800-3000 rpm for 10 PPS inputs), while the
electrical energy capture circuit still registers a sizeable
excess electrical power production (compare runs 11 and 12,
Table 7). Runs 13 and 14 illustrate how the charge pack's
state of charge and its inherent capacitance affects both
the PAGD frequency and the power producing efficiency of the
entire system: as the charge pack is reduced from 29 to 19
cells, the PAGD generator adjusts by reducing its frequency
logarithmically and, while the charge pack input current is
greater than before, the drive pack loss becomes still
larger and the breakeven efficiency much lower (by >1/2,
from 563% to 228%). This is because the circuit must
translate the naturally larger PAGD amplitude into a larger
surplus of output current, and in this process becomes less
efficient.
If the first measurement method employed (the
open circuit method) had to make too many theoretical
assumptions about the system's performance under load
conditions and hence about its effective charge capacity,
the second approach still had to suppose an invariant
discharge time and thus an invariant absolute charge
capacity on the part of the battery systems (charge packs)
employed for capture which it approximated by an operation
of integral calculus. With the third method described above,
theoretical assumptions were avoided except that, in these
measurements, the actual performance of a given battery in
terms of time, time of delivery and time of capture, was
also ignored; no account is taken of the time-dependent
modulation of the PAGD frequency, as effected by certain of
the parameters analyzed, namely the charge pack state of
charge, the method of sequencing the PAGD runs (continuous
vs interrupted) and its concomitant heating effects, and the
state of charge (load voltage and current capacity) of the
drive pack. A simple, non-negligible, resistive measurement
of power lost by the drive pack, and an identically
non-negligible measurement of the power gained by the charge
pack, for the same experiment and the same singular time of
PAGD production, were performed repeatedly to corroborate
the previous three approaches. For this purpose, all
experiments were designed as a continuous series of
sequential phases:
1) before a PAGD run, a resistive discharge
was measured across either pack over periods of 1 to 3 hours
(utilizing the DP and CP resistances previously reported in
the open voltage section) and followed by a 15 to 30 minute
open circuit voltage relaxation;
2) then, the PAGD runs were performed, either
continuously or as interrupted, composite sequences, and the
corresponding open circuit relaxation voltage(s) were
measured, after the cessation of the integral PAGD run;
3) finally, resistive discharge measurements,
obtained under identical conditions to those recorded before
the PAGD run, were carried out for either pack, followed by
concomitant battery voltage relaxation rate measurements.
Under these experimental conditions, exact
power measurements could be taken from an analysis of the
actual battery discharge curves before and after the PAGD
run. Based on a comparison of the curve trends of the
pre-run resistive discharge of the drive pack with those of
the post-run resistive discharge, the effective power drawn
(.DELTA.E.sub.c) from the withdrawable power capacity of the
drive pack incurred during a PAGD run, was ascertained. This
represents the power consumption during the run, and the
experimental value thus recorded constitutes the actual
power figure that must be matched for breakeven () to occur.
Hence, the breakeven value equals, by definition, the
electrical energy input to the system. Similarly, a
comparison of the charge pack pre-run and post-run resistive
discharge curve trends identified the effective power
(.DELTA.E.sub..rho.) added to the withdrawable capacity of
the charge pack. This quantity represents the electrical
energy recovered during the run. The relation for the two
quantities is expressed by the breakeven efficiency (BE
= %) equation:
%=.DELTA.E.sub..rho. /.DELTA.E.sub.c*100
If the breakeven efficiency is less than
%=100, then the apparatus registers a net loss in electrical
energy in the CP with respect to the DP. Conversely, if
%>100, then there is a net gain in electrical energy in
the CP, as compared to that lost in the DP. For purposes of
this analysis, a limit to the minimum withdrawable capacity
was placed, from experiment and in agreement with the load
current curves of the manufacturer, at 115 W for the driver
pack (average current of 0.250 A, minimum current of 0.230
A), and at 90 W for the charge pack (average current of
0.375 A, minimum current of 0.334 A), as a function of both
their total cell size (respectively, 46:29) and the
difference in the resistive loads employed for the discharge
measurements. All cathodes had been broken in, as described
before.
The results obtained with this fourth method,
for six selected experiments with three diverse types of
devices (using different electrode plate areas, gap lengths,
and electrode work-functions), configured both in the triode
or the (single) diode (e.g. FIG. 10B) arrangements, at the
indicated pressures, are presented in Table 8. In all cases,
a net excess of combined battery pack charge, expressed as
electrical watt hours, is registered (columns 8 and 10,
Table 8) and the breakeven efficiencies are all >100%
(column 10). Experimental groups #1 and #2 again demonstrate
that, for the same cathode, the interrupted PAGD sequence
method of group #2 (1 minute of PAGD function, followed by a
15 minute relaxation, and so on) yields a higher breakeven
efficiency because of the lower losses registered with this
minimal plate heating method (column 10, Table 8). Group #3,
Table 8, shows that the PAGD power production efficiency is
also higher for a lower work-function cathode material (H220
vs H34), being subjected to PAGD auto-electronic conditions
at a 4-fold lower pressure than the control groups #1 and
#2; however, the lower pressure depresses the frequency and,
together with the interrupted PAGD sequencing method, it
also lowers the loss, causing an actually much larger
breakeven value than registered for the previous two groups.
Groups #4 and 5 exemplify the dual effect of lowering both
the plate area and the gap distance: the former affects the
PAGD event frequency, whereas the latter affects the PAGD
amplitude, and thus the capture efficiency of the charge
pack. Despite a cathodic work-function practically and
operationally identical to that of groups #1 and 2, these
smaller plate area and shorter gap devices utilized in
groups #4 and 5, yield 3- to 6-fold lower net power outputs,
as well as lower breakeven efficiencies, than the former
groups, at the same pressure. Finally, group #6 exemplifies
the results obtained for the plate diode configuration,
where the frequency is lower (no triggering role for the
axial member), and a higher loss leads to the lower
breakeven efficiency, comparable to that of the lower area
and shorter gap groups #4 and 5.
In order to verify the discharge curve lengths
employed in these analyses and experimentally establish the
actual charge capacity of the battery packs, calibration
resistive discharges, between the maximum charge state and
the minimum limits chosen, were performed for each pack with
their respective discharge resistances R2 and R3 (see FIG.
9). These discharge calibration curves were plotted for half
maximal charge values shown in FIGS. 15A and 15B, and from
the curve produced, we have determined the total half-charge
capacities of each battery pack to be 1.033 kWh (100% =
2.066 kWh) for the drive pack and 660 Wh (100% = 1.320 kWh)
for the charge pack. Based upon the corresponding maximal
(100%) capacity values, we determined the actual percentages
of the relative charge capacities shown in column 5, Table
8, which correspond to the experimental values obtained. We
also noted that the curves plotted showed two quite distinct
time linear slopes, the slope of the delivery of power per
time unit steepening very markedly at the approach to the
limits of the permissible withdrawable capacity, occurring
at 115 W into R2, and 90 W into R3.
The pre-PAGD run and post-PAGD run, drive and
charge pack discharge curves corresponding to groups #3 and
#6, respectively for triode and plate diode configurations,
in Table 8, are shown in FIG. 16 (drive pack) and 17 (charge
pack), for group #3, and in FIG. 18 (drive pack) and 19
(charge pack), for group #6. In all cases, the open symbols
represent the pre-PAGD run discharge curves, whereas the
closed symbols represent the post-PAGD run discharge curves.
As a further check on these values, a
videographic, millisecond analysis of the singular power
simultaneities occurring at both ends of the system (drive
and charge packs) was performed for various 10 second
samples of diverse PAGD runs. A typical example is shown in
FIG. 20, which is a sample of the PAGD run designated as #6
in Table 8. Whereas the drive pack DC wattage spent as input
to PAGD production varied from 36.6 to 57.82 watts, by a
factor of 1.6x, the DC wattage entering the charge pack as
captured PAGD output varied more pronouncedly by a factor of
2.7x, from 146.4 to 399.6 watts (all meters were in the same
selected ranges of voltage and current) with the
semi-periodic, intermittent character of each singular
emission, though within specific, ascertainable ranges for
both amplitude and current outputs. Assimilation of the
singular behaviour of the PAGD in this sample, by a
statistical treatment of its variation (n = 64), indicates
that the operational breakeven efficiency observed during
this sampled period lies at 485.2%.+-.18% with projected
48.3Wh drive pack loss and 221.7Wh charge pack gain. This
matches rather closely the observed 483% breakeven
efficiency, and the 37.7Wh loss as well as the 182.2 kWh
gain for the overall PAGD run reported in group#6, Table 8,
and indicates how close are the values obtained by the
operational and extensive non-negligible resistive discharge
power measurement methods employed.
Finally, an example of the correlation between
the drive pack PAGD load voltage and the charge pack PAGD
charging voltage, as a function of the duration of the
intervening PAGD run between resistive discharge
measurements, is shown in FIG. 21, for the PAGD run
corresponding to group #4, Table 8.
Using the same pulse generator with H200 AL
128 cm.sup.2 plates, in a double diode configuration, and
the same circuit values (but with CP=23 cells), three
experiments were conducted at different PAGD frequencies, as
a function of varying air pressure. Analysis of driver pack
losses and charge pack gains by the extensive load discharge
measurement method, as described before, led to the
determination of the gross and net gains (respectively,
without and with losses included) per pulse, in
milliwatt-hour, for each frequency, as well as of the gross
and net power gains per second of PAGD operation. The
results are shown in Table 9. Even though the gross and net
gains of power per pulse were observed to increase with
decreasing frequency, the gross power gain per unit time
increased with increasing frequency. However, this last
trend does not necessarily translate into a higher net gain
per unit time, because the losses in the driver pack (not
shown) also increase significantly with PAGD frequency.
These losses are in all probability related to more energy
retention by the plasma at higher frequencies when plasma
extinction becomes incomplete. We expect net gains to reach
optimal thresholds for any given type of circuit
configuration set of values and pulse generator dimensions.
Certain additional observations made during
experiments with the double diode configuration of FIG. 10A
may assist in understanding of the invention.
1) Replacing residual air with argon gas leads
to higher PAGD frequencies, as noted by us when utilizing a
128 cm.sup.2 H200 AC plate pulse generator in the double
diode configuration (V=575). At 1 Torr, the pulsation rate
went from 20 PPS in air to 1300-400 PPS in argon. With 29*12
v cells in the charge pack, input currents ceased to flow
into it. Under these conditions, the tube potential across
the plates decreased and the drop across the input resistor
increased. The value of E( = V/d) became smaller (gap size=3
cm from plate to axial anode collector), as the extinction
voltage decreased.
2) With frequencies of 400 PPS, the currents
flowing into the charge pack fell to zero. Replacing a
fast-recovery type HFR 120 (1200v, 40A) diode bridge by a
type MUR 860 (600v, 8A) diode bridge had no effect. When the
amplitude of plate potential oscillations falls below the
potential of the charge pack, there is also a tendency to
produce arc discharges. For output currents from the vacuum
pulse generator to enter the charge pack, the number of
cells must be reduced so that the potential of the charge
pack is low enough to admit the transduced currents. A
reduction from 29 to 23 cells allowed currents of 250 mA to
enter the CP, and further reduction to 19 cells doubled
these currents (per polarity arm).
3) Our observations show that it suffices
under these conditions (CP = 19 cells) to increase the
vacuum, so that the frequency decreases, and the plate
potential and the charge pack input currents increase. At
0.1 Torr, the currents reached 1A D.C. per plate, and at
0.05 Torr, 2A D.C.
The interconnection between these factors
indicates that the extinction voltage is a function of the
PAGD frequency: the higher the PAGD frequency, the lower the
extinction voltage, until empirical (in distinction from
predicted) VAD field values are reached. As a consequence,
the start voltage of the charge pack must be adjusted, by
varying the number of cells composing it, so that it lies
below the lowest extinction voltage of the PAGD, for any
given geometry and gap distance.
Secondly, as the ion plasma is made more
rarefied, the frequency of the emissions decreases, but the
peak values of the output voltage and current per pulse
increase. The slower the PAGD and the more rarefied the
atmosphere, the higher is the output energy produced by the
system relative to the input energy.
Autographic analysis of PAGD-induced cathode
craters in H34 plates was performed, and their average inner
diameter and maximal depth were determined. Similar studies
were performed for PAGD-induced craters in Alzak (trade
mark) plates. The secondary craters characteristically found
in Alzak plates, along fracture lines irradiating from the
main crater, are absent in H34 plates; instead, in H34
plates, one observes a roughened surface surrounding the
emission crater, quite distinct from the original rough
aspect of the pulled finish of these hardened aluminum
plates. Also unlike the Alzak main craters, the H34 craters
often have a convex center occupied by a cooled molten metal
droplet, whereas the Alzak craters had a concave, hollowed
out aspect. Eventually, as the pitting resulting from PAGD
cathodic emissions covers the entire cathode, the metallic
surface gains a very different rough aspect from its
original appearance. In this process, craters from earlier
metal layers become progressively covered and eroded by
subsequent emissions from the same cathode. Altogether
different is the surface deposition process occurring at the
anode; here, the surface appears to become more uniform,
through the mirroring and possibly abrasive actions of
cathode jets. Macroscopically, with increased periods of
PAGD operation, the anode surface appears cleaner and more
polished.
With the data obtained by the metallographic
method of crater measurement, we estimated the volume of
metal ejected from the cathode, by assuming that the crater
represents a concavity analogous to a spherical segment
having a single base (1/6.pi.*H [3r.sup.2 +H.sup.2 ], where
H is the height of the spherical segment and r the radius of
the sphere), while disregarding the volume of the central
droplet leftover from the emission. The following are mean
.+-.SEM crater diameters (D), crater depths (H) and maximum
volumes (V) of extruded metallic material for two types of
aluminum cathodes, Alzak and H34 hardened aluminum, subject
to a high input current PAGD:
1- Alzak: D-0.028 cm.+-.0.003; H-0.002
cm.+-.0.0002; V-6.2*10.sup.-7 cm.sup.3 ;
2- H34: D-0.0115 cm.+-.0.0004;
H-0.0006.+-.0.0001; V-3.1*10.sup.-8 cm.sup.3 ;
Accordingly, utilizing plates composed of
either material with 3 mm of thickness, and thus with a
volume of 38.4 cm.sup.3 per plate and considering that only
2/3rds of the cathode shall be used (a 2 mm layer out of the
3 mm thickness), the total number of pulses per plate total
(TLT) and partial (PLT) lifetimes is theoretically:
1- Alzak: TLT: 6.2*107 pulses; PLT:
4.1*10.sup.7 pulses;
2- H34: TLT: 1.2*10.sup.9 pulses; PLT:
8.1*10.sup.8 pulses.
Typically, an H34 device can produce
.sup..about. 0.25 kWh per 10,000 pulses. The corresponding
value for a PLT is thus a minimum of 1.0 MWh/Alzak cathode
and of 20 MWh/H34 cathode. As the cathode for each
combination is only 66.7% consumed, the vacuum pulse
generator may continue to be used in a reverse
configuration, by utilizing the other plate in turn as the
cathode; thus, the estimated minimal values become,
respectively, 2.0 MWh/Alzak pulse generator and 40 MWh/H34
pulse generator. The same rationale applies for the double
diode configuration of FIG. 10C.
We have created a two-ported system for the
production of the singular discharge events which we have
previously identified in the '863 application as an
endogenous pulsatory abnormal glow discharge regime where
the plasma discharge is triggered by spontaneous electronic
emissions from the cathode. We have examined the functioning
of this two-ported system in order to determine what were
the electrical power input and output characteristics of a
sustained PAGD regime. Despite the wide (10-fold) variations
in net power and breakeven efficiencies measured by the four
different methods employed (open voltage measurements, time
integration of negligible power measurements, operational
power measurements and real time non-negligible power
measurements), all methods indicate the presence of an
anomalous electrical transduction phenomenon within the
vacuum pulse generator, such as can result in the production
at the output port of electrical energy measured and
directly captured which is greater than would be anticipated
having regard to the electrical energy input at the input
port. With the most accurate of the methods employed we have
found typical PAGD power production rates of 200 Wh/hour of
PAGD operation, and these may reach >0.5 kWh/h values.
The discrepancies between the methods utilized
have been extensively examined in the preceding section. Our
systematic approach demonstrates that the most frequently
employed method of measuring the charge capacity of
batteries by the open voltage values is the least reliable
approach for the determination of the actual net power lost
or gained by the battery packs used in the system: when
compared to all three other methods, it overestimates net
power consumed and produced by up to 10 fold, as well as
distorting the breakeven efficiencies, particularly at the
extremes of operation. All this results from the grossly
diminished (50-60% of manufacturer's theoretical estimate)
effective charge capacity of the lead acid gel cells
employed, as determined experimentally from FIGS. 18 and 19,
when compared to the theoretical maximal charge capacity
values that serve as scale for the open voltage
measurements. In other words, the effective energy density
of the batteries during these experiments was in fact
approximately half of the manufacturer's estimated 30 Wh/kg.
Under these actual conditions of battery
performance, the third and fourth methods (respectively,
operational and real-time non-negligible power measurements)
of power consumption and production proved to be the best
approach to measure both PAGD electrical power input and
output, as the results of both methods matched each other
closely, even though the former is a statistical treatment
of simultaneous events and the latter is a real time
integration of their cumulative effects. The second method
is clearly less reliable than either the third or the fourth
methods, and this stems from the fact that the power
consumption slopes of negligible resistive discharges not
only are very different from the quasi-steady state
discharge slopes (beginning at >5-15 minutes) of
extensive resistive discharges, but also their
proportionality may not reflect the real time
proportionality of equivalent prolonged resistive
discharges.
The main advantage of the fourth method is
that it effectively takes into account the actual time
performance of the batteries comprised by the overall PAGD
production and capture system we have described. As such,
the method may have the main disadvantage of reflecting more
the limitations of the batteries employed (their high rate
of degradation of the absolute value of total effective
charge capacity, and limited efficiency in retaining charge
derived from discontinuous input pulses) than indicating the
actual power output. There are a number of possibilities for
fine tuning of the system introduced by the present work,
beginning with the utilization of secondary batteries or
other charge shortage or absorption devices that have less
variable or more easily predictable actual charge capacity.
In this respect, there are two major shortcomings to the
batteries used to form the drive and charge packs; (1) their
significant memory effect and (2) their design for constant,
rather than discontinuous, DC charging. Recently developed
Nickel Hydride batteries are an example of an electrostatic
charge-storage system that lacks a substantial charge memory
effect, and their experimental batteries are being developed
currently for higher efficiency intermittent charging
methods. Electrostatic charge retention systems having
better energy densities, better charge retentivities and
insignificant memory effects will probably be more efficient
at capturing and holding the energy output by the circuit.
In practical embodiments of the invention, effectiveness in
charge utilization will be more important than
measurability, and any device that will use the energy
effectively whilst presenting an appropriate back EMF to the
system may be utilized.
The effect of the performance characteristics
of the drive and charge packs is only one amongst many
parameters affecting operation of the invention. As shown by
our extensive investigation of the diverse PAGD phenomenon
the recovery of energy from it by electromechanical
transduction as in the '531 application, or electrostatic
capture as described above, the factors involved in
modulating the frequency, amplitude and peak current
characteristics of the PAGD regime are complex. Manipulation
of these factors can improve electrical energy recovery, or
reduce it or even suppress PAGD. We have so far noted
numerous factors that affect PAGD frequency and some amongst
those that also affect the PAGD amplitude. Aside from these
factors, the circuit parameters of the output port portion
of the circuit, in addition to the nature and chemical
characteristics of the battery cells already discussed, the
charge potential of the charge pack, the characteristics of
the rectifiers in the recovery bridge in relation to the
period of PAGD superesonant frequencies, and the effective
values of the parallel and transversal capacitance bridges
can all influence the results achieved. Certain factors
however have a radical effect on PAGD operation, such as the
gap distance and the charge pack potential. Too small a gap
distance between the cold emitter (cathode) and the
collector will result in an increasing reduction in energy
recovery. The potential presented by the charge pack must be
less than the voltage amplitude developed by the PAGD, as
specified by a given gap distance at a given pressure. Too
large a charge pack size with respect to PAGD amplitude and
the gap length will preclude PAGD production or result in
extremely low PAGD frequencies. In brief, the energy
absorption rate and the counter potential presented by the
charge pack or other energy utilization device are important
factors in the operation of the circuit as a whole, and
should either be maintained reasonably constant, or changes
should be compensated by changes in other operating
parameters (as is typical of most power supply circuits).
Since our test results indicate that the
electrical power output of the circuit can be greater than
the electrical power input to the circuit, the circuit
clearly draws on a further source of energy input. Whilst we
do not wish to be confined to any particulary theory of
operation, the following discussion may be helpful in
explaining our observations. These observations have been
discussed in some detail so that the phenomenon observed can
be reproduced, even if the principles involved are not fully
understood.
In the '863 and '531 applications we have
identified a novel, cold-cathode regime of vacuum electrical
discharge, which we have termed the pulsed abnormal glow
discharge (PAGD) regime. This regime, which occupies the
abnormal glow discharge region of the volt-ampere curve of
suitable discharge tubes, has the singular property of
spontaneously pulsing the abnormal glow discharge in a
fashion which is endogenous to the tube and its circuit
environment that constitutes a vacuum pulse generator
device, when it is operated under the conditions we have
identified. In fact, when stimulated with continuous direct
current, in such conditions, such a circuit responds with
spontaneous abnormal glow discharge pulses that enable
effective segregation of input and output currents. We have
demonstrated electrically, metallographically,
oscillographically and videographically, how the pulsed
discontinuity results from a self-limiting, autoelectronic
cathode emission that results in repeated plasma eruptions
from the cathode under conditions of cathode saturated
current input. The auto-electronic triggering of the PAGD
regime is thus akin to that of the high-field emission
mechanism thought to be responsible for vacuum arc
discharges (VAD regime). However, under the PAGD conditions
we have defined, this mechanism is found to operate in the
pre-VAD region at very low field and low input average
direct current values, with very large interelectrode
distances and in a self-limiting, repetitive fashion. In
other words, the PAGD regime we have identified has mixed
characteristics: its current versus potential (abnormal
glow) discharge curve is not only distinct from that of a
vacuum arc discharge, but the electrical cycle of the PAGD
regime itself oscillates back and forth within the potential
and current limits of the abnormal glow discharge region, as
a function of the alternate plasma generation and collapse
introduced by the discontinuous sequencing of the
auto-electronic emission process. Accordingly, the
intermittent presence of the abnormal glow, as well as the
observed segregation of the current flows, are due to the
diachronic operation of these spontaneous cathode emission
foci. The micro-crater and videographic analyses of the PAGD
have demonstrated the presence of an emission jet at the
origin of each pulse, a phenomenon which VAD theory and
experiment has also identified. Metallic jets originating at
the cathode spots of VADs have been known to present
velocities up to, and greater than 1000 m/sec.
In light of the above, the energy graft
phenomenon we have isolated would have to be operated, at
the micro-event scale, by the interactions of the cathode
emission jet with the vortex-formed impulse-transducing
plasma in the interelectrode space. Several aspects can be
approached in terms of the complex series of events that
constitute a complete cycle of operation, on a micro-scale.
There are interactions within the cathode, interactions at
the cathode surface, interactions between the emission jet
and the plasma globule close to the cathode, and finally,
interactions of the resulting electron and ion distributions
in the interelectrode plasma, within parallel boundaries.
In general, in the presence of an electrical
field, the distribution of potential near the cathode forms
a potential barrier to the flow of electronic charge, as
this barrier is defined by the energy that the most
energetic electrons within the metal, the Fermi energy
electrons, must acquire before freeing themselves from the
cathode surface potential to originate an emission jet.
Before any free electrons become available for conduction in
the space adjoining the cathode, they must cross the
boundary posed by the potential barrier. With a weak applied
field, classical electron emission from a metal can only
occur if an energy practically equal to the work-function of
the metal is imparted in addition to the Fermi energy. Under
thermionic conditions of emission, the heating of the
cathode provides the needed energy input. However, the
cold-cathode Fowler-Nordheim quantum-field emission theory
predicted the existence of a finite probability for an
electron to tunnel through the potential barrier, when the
applied field is high. Cold-cathode electron emissions are
thus possible, under these conditions, at practically Fermi
energy levels, as the high field would catalyze the
tunnelling through the potential barrier by narrowing the
barrier width for the Fermi energy electrons. The exact
localization of the emission would then depend on the
randomized fluctuations of high fields at the cathode, which
were produced by positive space charges sweeping in
proximity to it. For most purposes, this theory has been the
working hypothesis of the last 60 years of field emission
studies, which have centered upon the VAD mechanism, despite
the fact that observed field gradients are evidently
inadequate to explain breakdown as a function of the
theoretical high field mechanism. The Fowler-Nordheim theory
has therefore suffered major revisions and additions, mostly
to account for the fact that it postulates, as a condition
for cold-cathode field emission in large area electrodes,
the presence of enormous fields (>10.sup.9 V/m) and
extremely low work functions, neither of which are borne out
by experimental VAD investigations. Some researchers have
found that the breakdown responsible for the VAD field
emission is promoted by Joule heating and vaporization of
microscopic emitter tips, and that this requires a critical
current density (10.sup.12 A/cm.sup.2), while others
emphasized that this explanation and these thresholds did
not hold for large area emitters and that a space charge
effect of concentrating the ion distribution near the
cathode promoted breakdown under these circumstances, when
the field reached a critical value; large field enhancement
factors (>1000-fold) have been postulated to explain the
discrepancy between theoretical predictions and experimental
findings regarding the critical breakdown field values, and
others have demonstrated how this critical field value
effectively varies with work-function and electrode
conditioning.
The PAGD regime and its self-extinguishing
auto-electronic emission mechanism stands as an exception to
the high field emission theory as it currently stands with
all its modifications, especially given that in this
phenomenon we are confronted.. with a cathode emission that
spontaneously occurs across the large gaps in large plate
area pulse generators, at very low field values (down to
<1*10.sup.4 V/m), as shown above and in the '863
application. Moreover, a Fowler-Nordheim plot (in the form
Log.sub.10 (I/V.sup.2) vs 1/V) of the PAGD volt-ampere
characteristic exhibits a positive slope, rather than the
Fowler-Nordheim negative slope characteristic of VAD field
emission. However, current density values obtained from
correlations of autographic analysis of the cathode with an
analysis of event-oscillogram (peak pulse currents),
indicate that the PAGD current density J may reach values of
10.sup.5 to 10.sup.7 A/m.sup.2 during the emission process
(the larger Alzak craters have an associated lower J value),
values which, at the upper end, do not reach the 10.sup.9
A/m.sup.2 current density threshold required by the
Fowler-Nordheim theory. Considering these two distinct
observations with regards to field strength and current
density, we have to admit the existence of a low field,
large area cold-cathode auto-electronic emission endowed
with high current densities, which is not predicted by
current field emission theory.
Unlike the typical VAD regime, the PAGD is
neither a high frequency oscillation, nor does it occur in a
random fashion. It constitutes a semi-regular,
quasi-coherent, periodic energy transduction which cycles
between cathode drop limits that are higher by a factor of
2-15 than typical vacuum arc cathode drops. The intermittent
cathode emission responsible for the low frequency, pulsed
behaviour of the abnormal glow, is also self extinguishing
and self-starting, under the conditions we have defined.
Furthermore, we have also identified a novel and unexpected
dependency of the periodic pulse rate upon the cathode area.
This indicates the presence of field emission control
parameters heretofore unsuspected. It is likely that field
fluctuations of the polarized pre-breakdown field is
responsible for eliciting the particular localizations of
the auto-electronic emission foci, as well as what imparts,
in a lens-like fashion, the distorted field energy needed
for electron surface release. In this sense, external,
electrical or magnetic field fluctuations (e.g. motion of
static charges or of constant magnetic fields) induced by us
at pre-breakdown potentials, provoked PAGD emissions and
breakdown at these levels.
In general, VAD studies have shown that, for
large area electrodes, microgeometry, adsorbed gas layers
and gas impurity contents of the cathode play a role in
modulating field emission. In our PAGD studies, the
interactions at the cathode surface and across the cathode
potential drop are clearly modulated by: (1) the nature of
residual gases, as shown by our air vs Argon studies; (2)
their pressure, (3) electrode conditioning, (4)
work-function and (5) cumulative pulse count, amongst
others.
The plasma, in leak-controlled or low pressure
PAGD devices, has both residual gas and metallic vapor
substrates. In devices initially closed at high to very high
vacua (diffusion pump pressures), the major residual
substrate, whose presence increases with time of operation,
is the metallic vapor released from the cathode and not
impacted onto the envelope walls or the anode. It has been
previously shown for externally (magnetically or
electrostatically) pulsed plasma accelerators, that the
amount of residual gas or vapor left in the interelectrode
space diminishes with increasing number of consecutive
discharges and a growing amount of electrode-insulator
absorption of gas. The effect of such removal of residual
gas or vapor is to decrease the vacuum of a sealed envelope.
With high vacuum sealed PAGD generators we have observed
that prolonged operation and sputter-induced mirroring of
the envelope causes a progressive disappearance of the
discharge, as the voltage potential needed to trigger it
also increases. At the thermocouple, low frequency pulsed
abnormal glow discharges can also be seen to increase the
vacuum significantly. These results suggest instead the
presence of a pumping mechanism in the PAGD which is
somewhat analogous to that of sputter ion pumps, where
collision of ionized gas molecules with the cathode is
responsible for the sputtering of cathode material that
either combines with the gas substrate (`gettering` action)
or `plasters over` the inert gas molecules onto the anode (a
process known as `ion burial`). These are the two basic
pressure reducing actions of sputtered getter atoms, in ion
pumps. However, in ion sputter pumps, the initiation of the
cycle is a function of the presence of high velocity
electrons in the high field plasma of the glow discharge,
which are necessary to ionize the gas substrate molecules;
also, the getter material typically has a high work-function
for field emission. Hence, the sputtering is due to the
secondary impact of plasma positive ions at the cathode,
after plasma ionization has occurred in the interelectrode
space. Altogether different is the mechanism of spontaneous,
primary electron emission from the cathode, which is
characteristic of the low field PAGD: here, the sputtering
is caused by the electronic emission itself and attendant
metallic vaporization processes. By artificially confining
the firing foci to a part of the cathode, we have shown in
the single diode configuration how the PAGD induced
sputtering is associated with the cathode autoelectronic
emission mechanism, rather than with the abnormal cathode
glow per se, given the localization of sputtering onto the
emission region of the plate, despite its overall cathode
glow saturation.
These observations would thus seem to
corroborate the hypothesis of a progressive vacuum increase
with the cumulative number of emitted pulses, were it not
for the fact that experiments performed with leak controlled
devices (reported here and in previous studies) show that,
when the negative pressure is maintained by balanced leak
admission of air or argon, pulse rates still decrease with
cumulative pulse count, and do so neither as a function of
an increase in vacuum, nor as a function of envelope
mirroring (unless this is so extensive as to establish
envelope conduction), but rather as a function of processes
(generally referred to as conditioning) inherent to the
electrodes, specifically, to the cathode. We have further
shown that, for such altered emitter states, the pressure of
the vessel must be increased, not because of an increasing
vacuum (precluded by the controlled gas leak), but because
of the effect that residual gases may have in modulating the
low field PAGD emission.
PAGD electrode conditioning is a
cathode-dominant process resulting from the cumulative
emission of high numbers of pulses by a cathode, and has
been shown to be a factor independent of the nature and
pressure of the residual gas and partially reversible only
by operation with reversed plate polarity, unlike reports of
copper cathode-dominant conditioning. It is thought that
electrode conditioning and the accompanying increase in VAD
breakdown potential are due to the progressive adsorption of
residual gases, though cathode-dominant conditioning
processes, such as subjecting the vacuum gap to consecutive
discharges, have been shown to correlate the decrease in
plasma impulse strength with electrode outgassing of
absorbed or adsorbed gases. Moreover, given the pitting
action of crater formation at the cathode by the PAGD
regime, and, as we shall see below, the metallic plating of
the anode, the PAGD cathode-dominant process of conditioning
we have observed with respect to decreased pulse frequency
and increase in potential, suggests that the apparent
increase in cathode work function is not due to gas
adsorption or absorption. These processes are more likely to
occur on the plated anode. It is likely that, given the
observed PAGD pressure reducing effect caused by the
cathodic jet, a certain outgassing of the cathode is in fact
occurring during PAGD function. One might also expect that
the anode, if plated by sputtering atoms, would increase its
gas content in the formed surface film. However, controlled
leak experiments suggest instead that some other type of
alteration of the cathode work function is occurring, which
is, as we shall examine below, independent of the adsorbed
gas state of the electrodes, as well as independent of the
PAGD ion pump-like effect. Nonetheless, even at the level of
the anode, the PAGD sputtering action may have contradictory
effects: it may impact interelectrode gap molecules onto the
collector, as well as release, by ionic bombardment and
vaporization, gases adsorbed to, or contaminating the anode.
If we assume that gas adsorption by impact on the collector
is the predominant mechanism, one could explain the increase
in the number of breakdown sites per unit time, as observed
by us for a re-reversed cathode, if the number of PAGD
breakdown sites depended on the quantity of adsorbed gases,
eg oxygen, on the cathode being tested. Recovery of the
cathode work-function would depend on the electronic charge
recovery of the positively charged, adsorbed or occluded gas
layer at the cathode- either by reversal or as a function of
time of inactivity. The surface film theory of `electrical
double layer formation at the cathode` in fact contended
that, low field flash over is a photocathodic effect
dependent upon the presence of a glowingly positively
polarized gaseous film at the cathode; this film would lower
the cathode emissivity by decreasing the field between the
cathode surface and the leading edge of the cathode glow,
across the cathode drop. However, even though the surface
film theory of `electrical double layer formation at the
cathode` predicts the lowering of the emission breakdown
potential and the increase in flash over rate when the
electrodes are reversed--as the anode would have acquired a
surface charge capable of affecting the breakdown potential,
it acknowledges nevertheless, that the anodic surface charge
hardly explains the observed intensity of the polarization
effects. Moreover non-reversed, conditioned cathodes
retained their lower PAGD frequencies in a time independent
manner, for as long as reversal was avoided (excluding a
PAGD frequency recovery effect due to plate cooling, which
may be as short as 15 minutes). PAGD conditioning was
independent of idle time and increased with cumulative pulse
count. Moreover, the AGD pulses are not UV photocathodic
Townsend discharges, liberating secondary electrons via
positive ion impact at the cathode. Nor could photocathodic
emissions generate currents of the magnitude observed in the
PAGD. Lastly, the PAGD discharge and breakdown thresholds
appear to be unaffected by UV, though they may be somewhat
depressed by visible light, and the emission mechanism in
the PAGD is the primary process.
Removal or flattening of protuberances and
tips from the emitting cathode by the action of the
discharge, is a process also thought to play a role in
hardening the cathode or increasing its field emission
work-function. However, this explanation may not be adequate
for the PAGD emission process, if we consider our
metallographic findings of a smoothing action of the
discharge at the collector. In fact, it would appear that
the flattened, smoother, plated, mirrored and cleaner
surfaces subjected to PAGD bombardment are the explanation
for the observed increased emission ability of re-reversed
cathodes: mirrored Alzak surfaces emit at higher frequencies
than do dull H34 and H220 surfaces; new, polished surfaces
emit at a higher frequency than do pitted, broken in
surfaces; anode surfaces, never before utilized as cathodes
but subjected to prolonged PAGD action, emit at higher
frequencies when employed as cathodes, than do new,
identical cathode surfaces; and ex-cathodes, employed for
prolonged periods as anodes, regain a higher emission
frequency upon re-use as cathodes. The better PAGD emission
performance of smoother cathodes, compared with the worse
VAD emission performance of the same, when pitted cathodes
(lacking protuberances) are used, requires explanation.
Rakhovsky has put forth a VAD model for
cathode spots, that distinguishes between Type I spots
(quickly moving spots, far from steady state and responsible
for crater formation), and Type II spots (quasi-stationary
and near steady-state, but leaving an itinerant track with
no sign of crater formation). Whereas the former would obey
the Fowler-Nordheim requirement for high fields
(>10.sup.9 V/m), the latter could hardly be expected to
do so with typical arc voltage drops in the order of 10 V.
Once again, autographic analysis of the PAGD emission aspect
indicates mixed characteristics: the PAGD cathode spot is a
hybrid. It behaves as an intermittent instability that
leaves single (e.g. in H34) or clustered (e.g. in Alzak)
craters, which are both qualities of Type I cathode spots;
and it exists under low field conditions (<10.sup.5 V/m),
with cathode drops of 20 to 150 V, in a quasi-coherent mode,
leaving an itinerant track of successive craters when
operating at the higher frequencies, all of which are
properties approaching those of a VAD Type II cathode spot.
Furthermore, the macroscopically visible metal sputtering
(due to the explosive action of the PAGD emission
phenomenon) occurring at the upper end of the permissible DC
current input scale, and the presence of large solidified
molten metal droplets in and around the craters, suggest
models which have been proposed for explosive electronic
emission. Explosion models propose that the creation of a
residual plasma ball in front of a microprotuberance
provokes the large potential drop at the prospective
emission focus and sufficiently high resistive and
Nottingham heating to reach >10.sup.7 A/cm.sup.2 current
densities during the explosive consumption of these
microemitters. Whether the explosive action associated with
cathode spots is an auxiliary effect that applies solely to
the vaporization of the emitting microprotrusion, or an
integral emission and vaporization explosive process, it
does not appear that it can be restricted to high-field VAD
Type II cathode spots, given that it can be equally made to
occur with the low field PAGD hybrid cathode spot, and be
macroscopically observed. Indeed, in the plate diode
configuration, it is easy to visualize the metallic particle
explosions that surround and accompany the plasma jets, near
to upper current limit conditions. However, if we are to
assume that any of these models apply to the emission
mechanism, we would, in all likelihood, have to conclude
that the PAGD initial emission sites must be submicroscopic
(100 to 10 nm), rather than microscopic. Resolution limits
to our own metallographic examination of the smoothing
action of the PAGD discharge on the collector would thus
have precluded us from detecting formation of such
submicroscopic protrusions, as well as their presence in a
`soft` cathode- and thus infer their disappearance from a
pitted, hardened cathode; but if the disappearance of such
submicroprotuberances were responsible for the observed
alteration of cathode work function, one would also thereby
have to postulate the existence of a mechanism for
microroughness regeneration (eg. tip growth) at the anode,
in order to explain the observed increased emission upon
cathode re-reversal. Furthermore, this regeneration would
have to be actively promoted by operation with reversed
polarity, and this is problematic. Focusing of the distorted
or magnified field upon alumina inclusions on pure iron
electrodes has been demonstrated to degrade breakdown
voltage for field emission, but the effect was greater for
larger microscopic particles. If we were to apply this
concept to our work, it would require the existence of
unmistakably abundant microscopic heterogeneities in the
quasi-homogeneous electrode surfaces employed, which we did
not observe; on the contrary, their absence suggests that
either the microroughness responsible for the low field PAGD
emission is submicroscopic, or that the field distortion
responsible for eliciting the PAGD is independent of the
presence of these protuberances. This last possibility must
be taken all the more seriously, in light of the fact that
PAGD functioning is able to cover with craters the entire
surface of an emitter.
Whereas the discharge potentials observed in
the PAGD have been shown to be relatively independent of the
kind of gas present, there is a gas effect in the PAGD
phenomenon, particularly in what concerns its frequency,
observed when the same `run down` cathode was capable of
much higher emission rates when exposed to argon, than to
air. Utilizing the technique of bias sputtering, it has been
demonstrated that the number of charge symmetric collisions
(dependent upon sheath thickness d and the ion mean free
path) in the plasma sheath, which are responsible for lower
energy secondary peaks in ion energy distribution N(E), at
pressures of 0.2 Torr, is substantially greater in argon
than in argon-nitrogen mixtures, and thus that, under these
conditions, mostly Ar.sup.+ and Ar.sup.++ ions impact the
negatively biased electrode. In non-equilibrium RF
discharges, greater ion densities have also been attained
with argon, than with air. With respect to field emissions,
one would expect a gas effect only with regards to changes
on surface conditions, though such studies have shown
contradictory effects of argon upon cathode work function.
In light of the foregoing, and given that the PAGD is an
emission discharge and not a sputtering discharge per se, in
the strict sense, we can conceive of the role of inert gas
atoms in increasing, as compared to air or nitrogen, the ion
energy density distribution at the PAGD cathode spot
interface with the cathode surface emitter, and thus elicit
increased emission rates from the cathode, by pulling
electrons from the metal via the field effect. While this is
consistent with the concept of focused distortions of
space-charge field fluctuations inducing localization of the
emission foci, the argon effect can be observed in the PAGD
regime over the entire range of the Paschen low vacuum
curve, and into Cooke's mid to high vacuum curve, at low
fields and without negative biasing. Thus, it is not simply
a high pressure (nor a gas conditioning) effect, even if the
gas effect in question applies to the description of a local
pressure rise at the emission site/cathode spot interface,
which may play a role in enhancing the local field.
Considered together, the PAGD emission-derived
sputtering, the observed metallic plating of the anode and
the explosive aspect of the discharge, suggest the presence
of a jet of metallic vapor present in the discharge and
running, contrary to the normal flow of positive ions, from
the cathode to the anode. This jet appears to have
properties similar to the high speed vapor ejected from the
cathode in a VAD, as first detected by Tanberg with his
field emission pendulum (Tanberg, R. (1930), "On the cathode
of an arc drawn in vacuum", Phys. Rev., 35:1080) In fact,
the VAD high field emission process is known to release,
from the cathode spot, neutral atoms with energies much
greater than the thermal energy of the emission discharge.
This anomalous phenomenon brings into play the role of the
reported cathode reaction forces detected in vacuum arc
discharges (Tanberg, as above, also Kobel, E. (1930),
"Pressure and high vapour jets at the cathodes of a mercury
vacuum arc", Phys. Rev., 36:1636), which were thought to be
due to the counterflow of neutral metallic atoms, from the
cathode onto the anode (charged metallic ions are normally
expected to target the cathode). In absolute units of
current, this current quadrature phenomenon has been shown
to reach, in the VAD regime, proportions of the order of
100*I.sup.2 (see also the Aspden papers referenced below).
Early interpretations attributed this to the cathode
rebounding of <2% of gas substrate-derived plasma
positive ions hitting the cathode and being charge
neutralized in the process, but having kept most of their
thermal energy. Tanberg held instead that the counterflow of
neutral particles responsible for the cathode reaction force
was cathode derived, effectively, that it constituted a
longitudinal interaction acting in the direction of the
metallic arc jet. However, even though secondary high energy
distributions of neutral atoms emanating from the cathode do
not have thermal energies, their modal distribution does
(Davis, W. D. and Miller, H. C. (1969) J. Appl. Phys.,
40:2212) furthermore, the major anomalous atomic counterflow
that accompanies the high energy electron flow toward the
anode, was shown mass spectrographically to consist
predominantly of multiply ionized, positively charged ions
of cathode metal, rather than neutral atoms. If this made it
easier to abandon the primacy of the rebounding model, it
was now more difficult for field emission theorists to
accept and explain the observed high energies (ion voltages
in excess of the discharge voltage drops) and the high
ionization multiplicity associated with these counterflowing
positive ions. This field of investigation has indeed been
one of the mounting sources of evidence suggesting that
there is something amiss in the present laws of
electrodynamics. The anomalous acceleration of
counterflowing ions, and the energy transfer mechanisms
between high speed or `relativistic` electrons and ions in a
plasma (Sethion, J. D. et al, "Anomalous Electron-Ion Energy
Transfer in a Relativistic-Electron-Beam-Heated Plasma"
Phys. Rev. Letters, Vol. 40, No. 7, pages 451-454), in these
and other experiments, has been brilliantly addressed by the
theory of the British physicist and mathematician, H.
Aspden, who first proposed a novel formulation of the
general law of electrodynamics capable of accounting for the
effect of the mass ratio factor (M/m') in the parallel (and
reverse) motion of charges with different masses, (Aspden,
H. (1969) "The law of electrodynamics", J. Franklin Inst.,
287:179; Aspden, H (1980) "Physics Unified", Sabberton
Publications, Southampton, England). The anomalous forces
acting on the counterflowing metallic ions would stem from
their out of balance interaction with the emitted high speed
electrons, as predicated by the electrodynamic importance of
their mass differential. This results in a fundamental
asymmetry of the plasma flow between electrodes, localized
onto the discontinuous interfaces of the plasma with the
electrodes, namely, in the cathode dark space and in the
anodic sheath: on the cathode side, electrons act upon ions,
as the emitted electrons having less than zero initial
velocities, drift against the incoming ion flux and in
parallel with the ion and neutral counterflows; on the anode
side of the discharge, positive ions flowing toward the
cathode confront mainly the incoming counterflow of positive
ions and neutral atoms, as the high speed electrons have
abnormally transferred their energy to counterflowing, high
speed, cathodic metal ions. An out of balance reaction force
thus results at the cathode, to which the leaving metallic
atoms impart a force of equal momentum but opposite
direction, a force which is added to the cathode momentum
generated by impacting, normal flowing positive ions.
Moreover, Aspden confirmed theoretically the fundamental
contention of Tanberg's experimental findings that an
electrodynamic force will manifest itself along the
direction of the discharge current flow, and thus, that the
atomic counterflow is a metallic jet. Aspden further
demonstrated that this asymmetry of plasma discharges does
not imply any violation of the principles of conservation of
energy and charge equivalence, given that there will be no
out-of-balance force when such anomalous forces are
considered in the context of the whole system of charge
which must, perforce, include the local electromagnetic
frame itself. Such discharges must be viewed as open energy
systems, in balance with their electromagnetic environment:
their apparatuses may constitute materially closed or
limited systems, but they are physically and energetically
open systems. Current work on Aspden's formulation of
Ampere's Law indicates that both classical electromagnetism
and special relativity ignore precisely, in circuits or in
plasma, the longitudinal interactions that coexist with
transverse ones. Standing longitudinal pressure waves, of a
non-electromagnetic nature, have been previously shown in
plasma electrons, which did not conform to the Bohm and
Gross plasma oscillation mechanism (Pappas, P. T. (1983)
"The original Ampere force and Bio-Savart and Lorentz
forces", I1 Nuovo Cimento, 76B:189; Looney, D. H. and Brown,
S. C. (1954) "The excitation of plasma oscillations" Phys.
Rev. 93:965)
The present theoretical approach to the novel
regime of electrical discharge which we have isolated in
specially designed devices, and to its mixed glow-arc
characteristics, suggests that a similar, out-of balance
current quadrature phenomenon occurs in the discharge plasma
during the low field, autoelectronic emission-triggered
PAGD, and is responsible for the observed surplus of energy
in the experimental system described in this report.
Clearly, all the evidence we have adduced indicates that
there is a powerful longitudinal component to the
emission-triggered PAGD, ie that the discharge pulses
characteristic of this pre-VAD regime are longitudinally
propelled jets of cathode-ejected high speed electrons and
high speed ions. We have performed experiments, in the PAGD
regime of operation, with very thin axial members that bend
easily when placed in the path of the discharge, or with
Crooke radiometer-type paddle-wheels, and both show the
presence of a net longitudinal force in the plasma discharge
acting in the direction of the anode, which confirms the
magnitude of the atomic counterflow (ionized and neutral)
present during the PAGD, very much like Tanberg's pendulum
did for the VAD. These observations also tally with the
explosive action of the emission mechanism, such as we have
examined it above. In this context, two aspects of the PAGD
are remarkable: the fact that a phenomenon akin to field
emission occurs at low field values, for large area
electrodes across large gaps, and the conclusion that the
PAGD must deploy an excessively large counterflow of, in all
probability, both ionized and neutral cathodic particles.
The observation of ion current contributions to the cathode
current on the order of 8 to 10%, in VADs, can hardly apply
to the PAGD mechanism responsible for the anomalous currents
and counterflows observed. Hence, we should further expect
that the characteristically intermittent, or chopped current
regime of the PAGD, is a major factor in the generation of
disproportionately high energy longitudinal pulses and in
allowing our system to capture most of the electrical energy
output from the device. In all probability, field collapse
at the end of discharge favours the nearly integral
collection of the plasma charge, and ensures the
transduction of most of the plasma energy of the pulse
(blocked, as it is, from flowing back through the input port
to the drive pack) to the output port, through the parallel,
asymmetric capacitance bridge that interfaces with the
charge recovery reservoir (the charge pack). Collapse of the
field of the discharge may also be a contributing factor to
the anomalous acceleration of ions, and to the observed
anode plating effect. It is equally possible that such
abnormally large longitudinal pulses may never be
observable, for a given arrangement and scale, above
threshold frequencies of the oscillation; we have, in this
sense, presented data that indicates that for a given
geometry, above specific PAGD frequencies, the capture of
surplus energy decreases steadily in efficiency until it
ceases altogether, for a given arrangement. The point at
which this surplus begins to decrease coincides with the
setting in of frequency-dependent irregularities in the
discharge sequence and, most importantly, it coincides with
a reduction of the peak pulse current for each PAGD pulse.
We have further remarked that increasing the PAGD frequency
above the zero surplus point, for a given arrangement, by
manipulating any of the frequency control parameters,
provokes the slippage of the PAGD into a full fledged VAD
regime, while input currents greatly increase and output
peak currents greatly decrease (to comparable peak input
levels of 10 to 15A). The transition between the two modes
of emission-triggered discharge, PAGD and VAD, thus appears
to be tied in to adjustable thresholds in the frequency of
the emission discontinuities; in this sense, it is rather
likely that the plasma field collapse plays a major role in
regularizing and optimizing the anomalous energies of field
emissions, as in the PAGD regime. At low frequencies of low
field emission, the emission regime is highly discontinuous,
diachronic and regular, for it has time to fully extinguish
the discharge; hence the PAGD singularity, in which the
phases of each discharge pulse are well defined and
sequential. Above a given high frequency, when ion and
electron recombination will happen more often, before each
can be collected at the electrodes, the stream of emitted
discontinuities merges into a noisy, randomized continuum,
where simultaneous emissions become possible and the plasma
field no longer has time to collapse and fully resolve the
longitudinal pulses. Any anomalous energy generated is then
minimized and trapped in the plasma body and, in these
conditions, the VAD regime eventually sets in. Such model
would easily explain why the high field VAD experiments
performed to date have never detected such extraordinarily
large anomalous forces.
On the other hand, the quasi-coherent aspect
of the discharge suggests that the vacuum gap, in
functioning during the PAGD regime both as an insulator and
as a conductor with capacitative and self-inductive
properties, is periodically altered by large and intense
polarizations which are resolved by the discrete emission of
longitudinal pulses from the cathode. It is possible that
these nonlinear oscillations resulting from sudden
depolarization of the vacuum gap by high speed explosive
emissions elicited at the convection focus of the distorted
field, might be in resonance or near resonance with the
external circuitry, but the most apparent effect of
increasing the capacitance in all bridge members is to
increase the jet current and the transduced current flowing
into the charge pack. The PAGD amplitude variation also
presents, after the large negative discontinuity, a growing
oscillation at very high resonant frequencies, which are
typical of inductive chopping currents in a VAD, before
extinction occurs. Unlike the VAD inductive case, in the
absence of any coils other than the wire wound resistors,
the PAGD relaxation oscillations which follow each pulse
only extinguish the discharge when the voltage potential of
the amplitude curve rises above the applied voltage, just as
the plasma potential drops the most. Given the entirely
non-inductive nature of the external circuit utilized in
many instances, the inductive properties in evidence are
those of the vacuum device itself. It also suggests that, in
the absence of any need of an applied external magnetic
field for the PAGD discharge to occur coherently, it is
possible that the magnitude of the currents generated
produces by itself a significant self-magnetic field. Thus,
we cannot rule out the possibility of a self-organization of
the plasma discharge, which may, in Prigogine's sense,
constitute a dissipative structure (Prigogine, I. and
George, C. (1977), "New quantization rules for dissipative
systems", Int. J. Quantum Chem., 12 (Suppl.1):177). Such
self-ordering of the PAGD plasma jet is suggested by the
experimentally observed transition of these pulses from the
current saturated limit of the normal glow discharge region,
into the PAGD regime, as a function of increasing current:
smaller foci of discharge can be seen to discontinuously
agglutinate into larger emission cones, or into jets with a
vortex-like appearance, when the input current reaches a
given threshold. It is possible that, under these
conditions, the distribution of the charge carriers and
their sudden fluctuations may render any steady state plasma
boundary conditions ineffective and provoke a singularity in
the discharge mechanism; this nonlinear behaviour, together
with any self-magnetic effects, might provide radial
coherence of the plasma flow along the longitudinal path of
the discharge. This concept is akin to what has been
proposed for periodically evanescent solution structures
referred to as instantons, that represent self-organizing
transitions between the two states of a system. The PAGD may
well be an instance of an instanton type structure bridging
the open, or conductive, and the closed, or insulating,
states of the vacuum gap. An analytical formulation of the
problem of the plasma flow from the cathode spot to the
anode, which would take into account the self-magnetic and
self-organizing properties of the PAGD plasma channel, would
be extremely difficult, given the out of balance
longitudinal force, its abnormal energy transfer and
associated counterflow, as well as the competition between
collisional and inertial exchanges.
The plating observed at the anode most likely
results from the impact of counterflowing ions (and possibly
neutral atoms), whereas the pitting of the (locally molten)
cathode results from the emission of vaporized metallic
material and electrons, as well as, secondarily, from
bombardment by incident positive ions. The first action
smooths the surface by mirroring it (deposition of
cathode-derived atoms) and abrading it, whereas the latter
smooths it in places by rounding concavities and by forming
molten droplets upon local cooling, while simultaneously
roughening it on the crater peripheries. One might think
that this cathode roughening should lower the work function
and facilitate the discharge, but the facts indicate that
just the opposite must be happening in view of changes in
the PAGD according to the nature and state of the cathode
surface. The observed alterations of electrode work function
for PAGD low field emission must thus be related to the
molecular and charge effects of these different actions at
the two electrodes. It appears that for large parallel plate
electrodes, the PAGD low field emission is modulated by the
nature and, most likely, by the molecular structure of the
metallic surface layer of the emitter.
We have thus devised a system for the capture
as electricity of the energy of anomalously energetic
longitudinal pulses sequentially triggered by spontaneous
emissions of high speed electrons and ions generated from
low work function cathodes, during the low field and
singularly mixed PAGD regime of electrical discharge in
vacuo. To confirm the above interpretation of the anomalous
flux in the observed PAGD phenomenon, the cathode jet
composition, as well as time- and usage-dependent changes
occurring in the tubes, with diverse sealed negative
pressures and after submission to prolonged PAGD operation,
must be analyzed mass spectroscopically. In any event, the
excess energy present in the anomalous counterflowing force
appears to stem from a discharge mechanism that effectively
pulls high speed electrons and constituent atoms out of a
metal surface, at low fields and with high current
densities, and is modulated by a complex multiplicity of
parameters. The system described appears to transduce
efficiently the observed nonlinear longitudinal pulse
discontinuities of the plasma field, under conditions of
current saturation of the cathode, because the
self-extinguishing and self-limiting properties of the
discharge allows the energy from the collapse of the
discharge to be captured. The particular design of the
circuitry, which couples a rectification bridge to the
asymmetric bridge quadrature of large capacitances, placed
at the output of the PAGD generator, permits effective
capture. Our findings constitute striking evidence for
Aspden's contention of a need to revise our present
electrodynamic concepts. The dual ported PAGD discharge tube
circuits which we have described are the first electrical
systems we know of which permit effective exploitation of
anomalous cathode reaction forces and allow for the recovery
of electrical energy from systems exhibiting this effect.
Any apparent imbalance in the electrical energy input to the
system and withdrawn from the system by its operator must be
considered in the context of the entire continuum in which
the system operates, within which it is anticipated that
accepted principles of energy balance will be maintained.
Moreover, the energy conversion system of the
invention has substantial utility as an electrical inverter
accepting direct current, and providing one or more of a
direct current output at lower voltage and higher current,
variable frequency input to alternating current motors, and,
by suitable combinations of discharge tube systems, more
flexible DC to DC conversion systems.
As an alternative to the batteries used in the
experiments described, a DC power supply may be utilized or,
more advantageously from the viewpoint of entailing less
transformation losses, a DC generator to provide the
electrical energy input to the system. As a DC motor can be
run directly from the rectified output of the circuit of
FIG. 9 at El-E2, in place of a battery charge pack, DC
motor/generator sets of suitable characteristics (in terms
of back E.M.F. and circuit loading) can be used to charge
the batteries of the drive pack, utilizing the rectified
PAGD output to drive the DC motor component of the set. This
provides a simple, one battery pack solution, where the PAGD
input and output circuits are electrically separated by the
DC motor/generator interface: the drive pack is
simultaneously being discharged to drive PAGD production,
and charged by the DC generator output which, in turn, is
being driven by the electromechanical transformation of the
rectified PAGD output that would typically accrue to a
charge pack in the experiments already described. The main
limitations to such an arrangement lie in the efficiency of
the motor and generator transformations utilized.
A pulsed DC source could be used to provide
input to the circuit if suitably synchronized, but care is
needed not to interfere unduly with the autoelectronic
mechanism of the field induced cathode emissions.
TABLE
1
______________________________________
Results for the ballast resistance (and
current) dependent PAGD
frequency utilizing an H34 aluminum pulse
generator with
128 cm.sup.2 plates at 5.5 cm distance,
in the triode configuration,
at a pressure of 0.8 Torr. The circuit
employed is that of the
present invention, as described in the
third Results Section.
DCV = 560.
Regime
of Pulse Rate
R in .OMEGA.
Discharge
>100 V
______________________________________
5,000
NGD
0
(Cold
Cathode)
600
PAGD
10 PPS
300
PAGD
40 PPS
150
PAGD
180 PPS
100
VAD
0
50
VAD
0
______________________________________
TABLE
2
______________________________________
128 cm.sup.2 H220 Al; 570 volts DC; 300
.OMEGA. = R1; Diode
Configuration
PPS
p(Torr) Cumulative Pulse Count
______________________________________
1)
200
0.08 .about.2.4 .times.
10.sup.5
2)
200
0.5 .about.1.5 .times.
10.sup.6
3)
200
0.8-1 .about.2.5 .times. 106
4)
25
0.5 3 .times. 10.sup.6
pulses
5)
200
0.5 1.5 .times. 10.sup.6
(after
first electrode reversal)
______________________________________
TABLE
3
______________________________________
RESIDUAL GAS EFFECT
pressure
PPS
in
Torr in
AIR in ARGON
______________________________________
0.45
ND
10
0.5
1.8 .+-. 0.3 ND
0.55
4.8 .+-. 0.9 16.7.+-.1.8
1.0
11.4 .+-. 0.8 448 .+-. 27.4
1.25
214.5 .+-. 14.3
ND
2.0
36.2 .+-. 2.6 206 .+-. 19.6
158.7
.+-. 24
2.5
1.36 .+-. 0.3 0
______________________________________
TABLE
4
______________________________________
Charge pack
No. of
cells PPS
PAGD
______________________________________
36
0
-
31
1
+
29
10
+
19
1
+
9
0
-
______________________________________
TABLE
5
__________________________________________________________________________
1
2
4
6 7
8 9
10 11
Expt.
Battery
3
Open 5 % total
Max.
%
rel. cpty
Total
.DELTA.kWh
PAGD
No. Pack
Position
Voltage
V/cell
rel.
cpty.
hr.
left
gained
lost
kWh
gain
loss
per
sec
__________________________________________________________________________
1 Charge
start
348
12.0
40
8
0.835 8
Charge
end
366 12.62
83
16.6
43
1.823
0.988
Driver
start
576
12.52
77
15.4 2.660
Driver
end
572 12.43
70
14 7 2.402 0.258
2 C
b 331 11.41
2
0.4
0.040 61
C
a 351 12.1
47.5
9.5 45.5 1.002
0.962
D
b 553 12.02
40
8
1.327
D
a 546 11.9
33
6.6 7 1.081 0.246
3 C
b 345 11.9
32.5
6.5
0.673 3
C
a 361 12.45
72.5
14.4
40
1.559
0.886
D
b 559 12.15
51
10.2 1.710
D
a 552 12.0
40
8 11 1.324 0.386
4 C
b 360 12.41
70
14
1.512 32
C
a 373 12.86
103
>20 33 2.238
0.726
D
b 562 12.22
54.5
10.9 1.838
D
a 557 12.11
48
9.6 6.5
1.604
0.234
5 C
b 340 11.7
20
4
0.408 2
C
a 365 12.59
83
16.6
63
1.818
1.440
D
b 527 11.45
3.2
0.6 0.101
D
a 517 11.24
1.8
0.4 0.2
0.056
0.045
6 C
b 340 11.72
21.5
4.3
0.438 8
C
a 367 12.66
87.5
17.5
66
1.927
1.489
D
b 589 12.8
100
20 3.530
D
a 564 12.26
58.5
11.7 41.5
1.979
1.551
7 C
b 318 10.97
1.2
0.24
0.023 5
C
a 359 12.38
67.5
13.5
66.3
1.454
1.431
D
b 575 12.5
77
15.4 2.656
D
a 567 12.32
63.5
12.7 13.5
2.160
0.496
8 C
b 328 11.71
20
4
0.393 32
C
a 350 12.5
76.5
15.3
56.5
1.606
1.213
D
b 582 12.65
87.5
17.5 3.055
D
a 579.5
12.60
84
16.8 3.5
2.921
0.134
__________________________________________________________________________
1
2 12
13 14
15 16
18
Expt.
Battery
3
Exptl.
rel.
kWh/h
net
kWh/h
Breakeven
Cell
#/
17
Cathode
19
No. Pack
Position
time
gain
loss
production
efficiency
pack
tube
Area
Plate
__________________________________________________________________________
1 Charge
start
21.5'
2.071 388% 29 A26
128
cm.sup.2
H34
Charge
end
2.791
Driver
start
46
Driver
end
0.720
2 C
b 18'
2.387 391% 29 A26
128
cm.sup.2
H34
C
a 3.207
D
b
46
D
a
0.820
3 C
b 21.5' 1.396
230% 29 A26
128
cm.sup.2
H34
C
a 2.473
D
b
46
D
a
1.077
4 C
b 63.5' 0.465
310% 29 A28
128
cm.sup.2
H220
C
a 0.686
D
b
46
D
a
0.221
5 C
b 80'
1.064 6,750%
29
A26
128
cm.sup.2
H34
C
a 1.080
D
b
46
D
a
0.016
6 C
b 21.5' -0.173
96%
29 A26
128
cm.sup.2
H34
C
a 4.155
D
b
46
D
a
4.328
7 C
b 64.5' 0.870
289% 29 A45
64
cm.sup.2
H34
C
a 1.331
D
b
46
D
a
0.461
8 C
b 28.5' 2.272
906% 28 A45
64
cm.sup.2
H34
C
a 2.554
D
b
46
D
a
0.282
__________________________________________________________________________
1
2 20 21
22 23 25
26 27 28 29
Expt.
Battery
3
R1 C3/C5
C7a/C7b
Motor
24
Gap
OV
rlx.
C4
R4 Motor
No. Pack
Position
ohm
mfd
mfd arm Pressure
cm
time mfd
ohms
rpm
__________________________________________________________________________
1 Charge
start
300
20,700
3,300
off
0.8 Torr
5.5
30'
NA NA NA
Charge
end
Driver
start
Driver
end
2 C
b 300
20,700
3,300
off
0.8 Torr
5.5
30'
NA NA NA
C a
D b
D a
3 C
b 300
20,700
3,300
off
0.7 Torr
5.5
15'
NA NA NA
C a
D b
D a
4 C
b 300
34,700
5,500
off
0.2 Torr
5.5
30'
NA NA NA
C a
D b
D a
5 C
b 150
34,700
3,300
on
0.8 Torr
5.5
15'
8 500
1,200
C a
D b
D a
6 C
b 300
20,700
3,300
on
0.8 Torr
5.5
15'
16 0 2,000
C a
D b
D a
7 C
b 600
34,700
3,300
off
0.8 Torr
4
30' NA NA NA
C a
D b
D a
8 C
b 600
34,700
5,500
off
0.8 Torr
4
30' NA NA NA
C a
D b
D a
__________________________________________________________________________
TABLE
6
__________________________________________________________________________
Expt.
Battery
Load Watts/ Total
.DELTA.kWh
rel.
kWh/h
net
No. Pack
Position
Voltage
cell
Hr.
left
kWh
gain
loss
gain
loss
kWh/h
B.
Eff.
__________________________________________________________________________
1 C
s 335.7
4.445
4
0.516
3.014
776%
C
e 357.5
5.05
12
1.757
1.241
3.46
D
s 568.0
3.20
13
1.766
D
e 564.6
3.175
11
1.606 0.16 0.446
2 C
s 315.5
3.93
1
0.114
1.012
504%
C
e 327.8
4.25
4.5
0.502
0.387
1.225
D
s 540.7
2.91
4
0.535
D
e 535.3
2.87
3.5
0.462 0.073 0.243
3 C
s 328 4.23
2
0.245
1.175
703%
C
e 351.7
4.91
7
0.737
0.492
1.370
D
s 546 2.95
5
0.680
D
s 545.5
2.90
4.5
0.610 0.070 0.195
__________________________________________________________________________
TABLE
7
__________________________________________________________________________
1
3 5
6 7 8
9 10 11
Expt.
2
Pressure
4
DP Plates
DP
DP PAGD
PAGD
CP
No. Config.
Torr
Tube
DCV
DCV DCA Watts
Volts
V/cm
DCV
__________________________________________________________________________
1 dd 0.8 A29 562
350 0.65 137.8
212
77.1 375
2 dd 0.09 A29 562 402
0.60 96 160 58.2 378
3 dd 0.8 A29 560
371 0.59 111.5
189
68.7 374
4 dd 0.09 A29 563 409
0.49 75.9
154
56 379
5 t 1.5 A28
561 439 0.41 49.9
122
22.2 377
6 t 1.5 A28
560 425 0.51 68.9
135
24.5 375
7 t 1.0 A28
556 398 0.48 75 158 28.7 376.5
8 t 0.5 A28
559.5
398
0.68 109.8
161.5
29.4
377.5
9 t 0.5 A28
563 390 0.75 112.45
173
31.5 373
10 sd 0.5 A28 565 422
0.47 67.2
143
26 376
11 sd 0.5 A28 561.5
415
0.50 73 146.5
26.6
380
12 sd 0.5 A28 562 413.5
0.55
81.7
148.5
27
380
13 dd 0.25 A28 553 438 0.35
40 115 41.8 381.5
14 dd 0.25 A28 549 325 0.70
156.8
224
81.5 263
__________________________________________________________________________
1
12 13 14
15 17 18 19
Expt.
2
CP CP Total Breakeven
16
Bridge
Input
Motor
20
No. Config.
DCA
Watts
Resistance
Efficiency
PPS
diode
diode
status
FIG.
3
__________________________________________________________________________
1 dd 1.25
468.8
326
340% 450
M860
HFR
off +
2 dd 0.70
264.6
%
270 276% 92 M860
HFR
off
3 dd 0.65
243.1
243
218% 500
HFR
HFR off
4 dd 0.76
288
314 379% 77 HFR HFR off
5 t 0.58
219
298 439% 52 HFR HFR off
6 t 0.69
259
265 376% 100
M860
HFR
off
7 t 0.57
213.1
329
284% 355
M860
HFR
off
8 t 0.67
252.9
238
230% 92 HFR HFR off
9 t 0.65
280
266 249% 118
M860
HFR
off +
10 sd 1.03
387.3
286
530% 25 M860
HFR
off
11 sd 0.73
277.4
293
379% 11 HFR HFR off +
12 sd 0.71
269.8
270
330% 10 HFR HFR on +
13 dd 0.59
225.1
329
563% 10 HFR HFR off
14 dd 1.36
257.7
320
228% 1 HFR HFR off
__________________________________________________________________________
TABLE
8
__________________________________________________________________________
1
2
4 5
7 8
9 10
Expt.
Battery
3
Total
Rel.
6
Limit
.DELTA.kWh
Exptl.
abs.
kWh/h
11
No. Pack
Position
Wh
Cap.
Torr
in
W gain
loss
time
gain
loss
net
BE
__________________________________________________________________________
1 C
b 159 12% 0.8
90
21.5'
+664
846%
C
a 428
32%
269 753
D
b 1764 85% 115
D
a 1732
84%
32 89
2 C
b 118 9% 0.8
90
18'
+616
2,667%
C
a 303.5
23%
192
640
D
b 542.3
26%
115
D
a 535
25.9%
7.3 24
3 C
b 950.4
72%
0.2
90
70'
+186
3485%
C
a 1,161
88%
210.9
191.7
D
b 660 32% 115
D
a 654
32%
6.5 5.6
4 C
b 15.8 1.2%
0.8
90
64.5'
+53.7
406%
C
a 81.9
6%
65 60
D
b 181 8.7% 115
D
a 165
8%
16
14.7
5 C
b 34.5 2.6%
0.8
90
28.5'
+169.1
436%
C
a 138.8
10.5%
104.3
219.6
D
b 1,114
54%
115
D
a 1,089
53%
24
50.5
6 C
b 55.4 4.2%
0.8
90
74'
+117
483%
C
a 237.6
18%
182.2
148
D
b 669.3
32%
115
D
a 631.7
30.6%
37.7
30.6
__________________________________________________________________________
1
2
14
15 17 18
19 21 22
Expt.
Battery
3
12 13 Cathode
gap
16
PAGD seq.
R1
Plate C3/C5
C7a/C7b
No. Pack
Position
Config.
Tube
area
cm PPS
method
ohms
material
20
mfd
mfd
__________________________________________________________________________
1 C
b Triode
A26
128
cm2
5.5
8
Continuous
300
H34
20,700
3.300
C a
D b
D a
2 C
b Triode
A26
128
cm2
5.5
61
Interrupted
300
H34
20,700
3,300
C a
D b
D a
3 C
b Triode
A28
128
cm2
5.5
32
Interrupted
300
H220
34,700
5,500
C a
D b
D a
4 C
b Triode
A46
64
cm2
4.0
5
Continuous
600
H34
34,700
5,500
C a
D b
D a
5 C
b Triode
A46
64
cm2
4.0
32
Interrupted
600
H34
34,700
5,500
C a
D b
D a
6 C
b Plate
A29
128
cm2
5.5
8
Interrupted
300
H220
34,700
5,500
C
a Diode
D b
D a
__________________________________________________________________________
TABLE
9
______________________________________
Utilizing:
Al H200, 128 cm.sup.2 plates
DP = 46 cells
CP = 23 cells
CP
Gain
Net
Gain
CP
Gain Net Gain per per
per
pulse
per
pulse
second
second Pressure
PPS in
mWh mWh
mWh mWh in Torr
______________________________________
#1 1.5
22.3 11.7 33:45
17.55 0.2
#2
8
5.6 4.4
44.8 35.2 0.8
#3 110
0.78 0.27
85.8 29.7 2.0
______________________________________
US Patent # 5,502,354
US Cl. 315/111/01 ~ March 26, 1996
Direct Current Energized Pulse
Generator Utilizing Autogenous Cyclical Pulsed
Abnormal Glow Discharges
Paulo N. Correa & Alexandra N. Correa
Abstract ~
A cold cathode vacuum discharge tube is used
in a circuit for generating pulsed autoelectronic emissions
which are particularly intense and frequent in the abnormal
glow discharge region, and involve much lower current
densities than predicted by the Fowler-Nordheim vacuum arc
discharge region law. The discharge tube is characterized by
a large electrode area at least of the cathode, and a large
interelectrode gap. The electrodes are preferably spaced at
least 2 cm apart in a parallel relationship. A probe may be
introduced between the electrodes to reduce still further
the field required to generate the emissions. In another
configuration the probe forms the anode and two plates form
cathodes. The circuit is driven from a direct current source
of having an impedance sufficient to prevent establishment
of a vacuum arc discharge.
Current U.S. Class: 315/111.01; 315/339;
315/349
Intern'l Class: H01J 007/24
Field of Search:
315/111.11,111.21,111.01,111.71,111.91,56,61,63,339,349
References Cited ~
US Patent Documents
3,471,316 ~ Sep., 1969 ~ Manuel 117/93.
3,821,580 ~ Jun., 1974 ~ Alexandrovich et al. 313/56.
4,733,530 ~ Mar., 1988 ~ Beattie et al. 315/111.
Primary Examiner: Pascal; Robert J. ~
Assistant Examiner: Ratliff; Reginald A.
Attorney, Agent or Firm: Ridout & Maybee
Description ~
FIELD OF THE INVENTION
This invention relates to cold cathode vacuum
discharge tubes and in particular to their use in a field
emission, cold cathode vacuum tube circuit, hereinafter
referred to as a pulse generator, having a large cathode
area and large interelectrode gap which, if properly
triggered, will generate pulsed auto-electronic emissions in
the abnormal glow discharge region.
BACKGROUND OF THE INVENTION
As the current passed through a gas discharge
tube is increased beyond the levels at which normal glow
discharge takes place, such normal gas discharge being
characterized by a negative resistance characteristic
leading to decreasing potential between the cathode and
anode electrodes of the tube, a region of abnormal glow
discharge is entered in which the negative resistance
characteristic changes to a positive resistance
characteristic leading to increasing potential between the
elecytrodes. Typically this increased potential rapidly
leads to breakdown into vacuum arc discharge between the
electrodes, again characterized by a negative resistance
characteristic. Accordingly, gas discharge tubes have been
operated in the normal glow discharge or vacuum arc regimes
in which stable operation can be achieved by appropriate
ballasting of the tube, the former regime being suitable for
low current applications and the latter for high current. It
is possible to utilize a normal glow discharge tube in a low
frequency oscillator circuit by placing capacitance in
parallel with the tube and in series with the ballast
because such a tube is characterized by a comparatively high
striking potential at which discharge is initiated, and a
lower but still high extinction potential at which discharge
ceases. Operation in such a mode with vacuum arc devices is
difficult because, in order to turn off the device
effectively, the arc must be extinguished or otherwise
interrupted or divested for long enough to disperse the
intense ionization formed in its path. On the other hand,
the current densities of normal gas discharges are too
limited for use in applications requiring relatively large
currents.
Devices operating in the vacuum arc regime
have other problems, particularly in terms of ensuring
adequate electrode life, which have led to gas diodes and
triodes (thyratrons) being superseded by semiconductor
devices in most applications. A further limitation of such
devices is that the great difficulty in turning them off,
except by terminating current flow through the device for a
finite period, limits their usefulness as control devices to
rectification, current turn-on and low frequency alternating
current applications.
The only prior art of which we are aware which
successfully exploits the abnormal glow discharge regime is
the process described in U.S. Pat. No. 3,471,316 (Manuel)
issued Oct. 7, 1969, which we understand is commercially
utilized in forming organic coatings on metal cans. It
relies on the application of externally generated current
pulses to force a discharge tube temporarily into the
abnormal glow discharge region, the pulses being
sufficiently short that no vacuum arc is established. There
is no disclosure of any endogenous pulsed abnormal glow
discharge, the apparatus is dependent upon an external pulse
generator to operate, and its utility is completely
different from the present invention because it uses
externally generated pulses rather than generating such
pulses. U.S. Pat. No. 3,471,316 uses externally generated
and limited current pulses to project operation of a
discharge tube in a transient manner into the abnormal glow
discharge region, thus achieving a higher average current
density and accelerating the polymerisation process beyond
the rate attainable using a normal glow discharge.
SUMMARY OF THE INVENTION
The problems associated with the operation of
vacuum arc devices are typically associated with the
establishment of a continuous channel of low resistance
ionized plasma between the electrodes of a device operating
in this mode, accompanied by intense heating of the
electrodes. Such a channel is difficult to interrupt in
rapid and predictable manner once established. We have
discovered that it is possible to set up a stable endogenous
pulsed abnormal glow discharge regime which is characterized
by no such continuous channel having been established, and
predominantly cold-cathode auto-electronic field emission
rather than thermionic emission, these characteristics
providing the ability to control and extinguish the
discharge readily.
We have found that, by use of a suitable
design of a low pressure gas discharge tube, we can
sufficiently inhibit transition from the abnormal glow
discharge regime into the vacuum arc discharge regime that
we can successfully exploit characteristics of the abnormal
glow discharge regime to provide a device having valuable
and controllable characteristics as a high power, pulse
generator when fed from a current source. Such a pulse
generator has useful applications in for example motor
control and other applications requiring high current
pulses. It is a valuable characteristic that the pulse
repetition frequency can be varied over a range, the extent
of which itself varies according to the physical
characteristics of the tube and the environment in which it
is operated. According to circumstances, the frequency may
range as low as 10 pulses per second or range as high as
10.sup.4 pulses, these figures being exemplary only and not
limitative.
Most prior art vacuum arc discharge has been
performed with devices having short interelectrode gap
lengths and small electrode areas. Prior art devices require
the application of large kilovoltages and amperages, vacuum
arc discharges in those devices being initiated by contact
and separation of the electrodes. We have established that
vacuum devices equipped with cathodes having large surface
areas and having large interelectrode distances will support
field-emission discharges (either of the pulsed abnormal
glow or the vacuum arc type) at low DC voltages (ie. low
field strengths) and low applied currents. This indicates
that the cold-cathode emissions observed (pulsed abnormal
glow discharge and the vacuum arc discharge) in this new
class of vacuum pulse generator are a function of parameters
heretofore ignored or undiscovered.
The present invention provides a pulse
generator and a method of pulse generation as set forth in
the appended claims.
DESCRIPTION OF THE DRAWINGS
The invention will be further explained by way
of example only and with reference to the following
drawings, wherein:
FIG. 1
is a graph illustrating the current to voltage relationship
exhibited by a notional vacuum discharge tube;
FIG. 2
is a graph illustrating the current to breakdown, extinction
(PAGD) and sustaining (VAD) voltages of a particular vacuum
discharge tube;
FIG. 3
illustrates a discharge tube for a pulse generator having a
glass housing and tetrode geometry;
FIG. 4
illustrates a tube having a polymer housing and a triode
geometry;
FIG.
5 illustrates central cross sections of two
glass housings (FIGS. 5A and 5B) and a polymer housing (FIG. 5C);
FIG. 6
illustrates volt-ampere linear characteristics of two
distinct cold-cathode discharge regimes, PAGD and VAD, in
the same tube providing the curves of FIG. 2;
FIG. 7
illustrates a Fowler-Nordheim plot of the Vx or Vs values
for the PAGD and VAD regimes, respectively, again in the
same tube;
FIG. 8
illustrates the pulse per minute rate variation observed as
a function of low current, anode-supplied constant DC
voltage for two pulse generators
FIG. 9
illustrates the continuous variation of the pulse per minute
rate as a function of anode-supplied or cathode-supplied DC
voltage;
FIG.
10 illustrates an increase in the pulse
frequency per minute as a function of the peak pulse RMS
current;
FIG.
11 illustrates a continuous variation of NGD
sustaining/PAGD extinction voltages, from breakdown to glow
extinction, with decreasing pressure, in 4 discharge tubes
having different plate areas;
FIG.
12 illustrates a continuous variation of PAGD
frequency with decreasing gas pressure in 3 discharge tubes
having different anode and cathode plate areas;
FIG.
13 illustrates a shift of the PAGD regime to
higher pressure regions during pumpdown with a rotary vacuum
pump;
FIG.
14 illustrates a shift of the PAGD regime to
lower pressure regions and higher frequencies during
pumpdown;
FIG.
15 illustrates the observed reductions in device
pressure (FIG. 15A) and in voltage (FIG. 15B) as
a function of the increase in plate area factor, for the
three discharge tubes having different plate areas
stimulated with low direct current during argon pumpdown
under the conditions described in FIGS. 11 and 12;
FIG.
16 illustrates observed effects of plate area
upon the PAGD breakdown (Vb) and extinction (Vx) voltages
for 7 separate discharge tubes;
FIG.
17 illustrates the effect of plate area upon
input DC and transduced RMS currents in 7 discharge tubes;
FIGS.
18A, B and C are oscillograms depicting AGD
pulses in different regions of a circuit as shown in FIG.
20B;
FIG.
19 illustrates an effect of varying the
capacitance of a power supply in parallel with the tube, on
the frequency of PAGD production;
FIGS.
20A and B show two typical wiring diagrams of
pulse generators in accordance with the invention; FIG. 20A
illustrates the circuit used in the tests that supplied data
for FIGS. 5 to 15, and 19; FIG. 20B illustrates the circuit
used for test results illustrated in FIGS. 16 to 18; and
FIGS.
21A and 21B show alternative configurations in
which the tubes described can be incorporated into a pulse
generator.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The context of the invention in terms of
vacuum discharge phenomena will first be discussed with
reference to FIGS. 1 and 2. Referring to FIG. 1, which plots
the potential between the principal electrodes of a vacuum
discharge tube with increasing current, potential being
shown on a linear but arbitrary scale of voltage, and
current on a logarithmic scale in amperes, curve A, below
its intersection with curve B, represents a typical
relationship between current and voltage for cold cathode
discharges, including auto-electronic emissions, whilst
curve B represents a typical relationship for thermionic
glow discharges, including thermionic emissions. The
high-current intersection of the two curves at point E
represents a transition into the vacuum arc discharge (VAD)
region (curve C) with the establishment of a continuous low
resistance plasma channel between the electrodes.
It will be noted that curve A exhibits, with
increasing current from very low levels, an initially rising
voltage or "positive resistance" characteristic, through the
Townsend discharge (TD) region, a flat characteristic
through the constant discharge (CD) region, a falling
voltage or "negative resistance" characteristic through the
transitional region discharge (TRD) and normal glow
discharge (NGD) regions, to a minimum, before once again
rising to a peak of F and then falling to an even lower
minimum, equal to the sustaining voltage for a vacuum arc
discharge, through the abnormal glow discharge (AGD) region.
The rising potential over the first portion of the AGD
region is believed occasioned by saturation of the
electrodes by the glow discharge, which causes the potential
to rise until auto-electronic emission sets in allowing the
potential to fall again as the current rises further. In
practice, the increasing interelectrode potential-following
saturation, and other factors such as electrode heating,
leading to thermionic emission, will tend in conventional
tubes to result in a premature transition from the AGD into
the VAD regime, following a curve similar to curve D shown
in FIG. 1.
The present invention relies on the use of gas
discharge tubes designed to avoid premature transition from
the AGD to the VAD regimes, and capable of being operated in
a stable manner in that region of the characteristic curve
of FIG. 1 extending between points E and F. FIG. 2, which
plots test results for just such a tube, constructed as
described below, shows, again on similar coordinates to FIG.
1 (except that the potential units are defined), the
extinction or sustaining potentials of the tube (the same
information as plotted in FIG. 1), together with the
breakdown potential (i.e. the potential required to initiate
the autoelectronic discharge). It will be noted that the
breakdown curve shows two discontinuous portions X and Y,
corresponding to the vacuum arc and abnormal glow discharge
regimes respectively. The intersection of curve X, and curve
Z representing the sustaining or extinction potential is
illustrative of the difficulties inherent in extinguishing a
vacuum arc discharge, since a decrease in current is
accompanied by a decrease in breakdown voltage until it
equals the VAD sustaining voltage which does not vary
greatly in this region. On the other hand, the combination
of a fairly high and constant breakdown voltage (curve Y)
combined with an extinction potential which rises with
decreasing current in the region E-F (see FIG. 1) of the
pulsed abnormal glow discharge regime means that the pulsed
abnormal glow discharge will be extinguished if the current
source during the tube operation ceases to be able to
sustain the increasing current required to maintain the
discharge as the potential between its electrodes drops, at
some current below the intersection of curves X and Z.
If the effective internal resistance of the
source is above some critical level, then as the current
through the tube rises, the proportion of the source
potential developed across the tube will fall until it
intersects the curve Z at a current below the intersection
with curve X, at which point the abnormal glow discharge
will self extinguish, and the current flow through the tube
will drop abruptly until the current through the tube
combined with the potential between its electrodes again
intersects the curve A in FIG. 1. This permits
reestablishment of a rising current through the tube
traversing the abnormal glow discharge region as the
potential across the tube rises to the peak F and then again
falls to a point short of E. Accordingly, under these
circumstances, a pulsed abnormal glow discharge will be
exhibited, accompanied by high amplitude current pulses
through the tube. It should be understood that the curves of
FIG. 1 are indicative of the static behaviour of a nominal
discharge tube under particular current and voltage
conditions, and are not fully indicative of the behaviour of
the tube under dynamic conditions in which tube current and
inter-electrode potential vary with time, nor with changes
of the many other factors which may influence tube
behaviour. In particular, the plasma effects generated in
various phases of tube operation require finite time to
form, reform or dissipate as the case may be, and in the
case presently under consideration this time factor,
combined with time constants of the external circuit in
which the tube is placed, are determinative of the pulse
frequency of the discharge.
The definition of any regime of electrical
discharge in a vacuum is usually presented as dependent upon
the major operational parameter being considered, i.e. upon
the variation of direct current passing between the primary
electrodes. For a given optimal vacuum (which must
necessarily be less than perfect) all gas electrical
discharge regimes can be presented as dependent upon this
parameter. FIG. 1 is such a presentation and the peak that
characterizes the abnormal discharge region means that
within this region, as the applied current is increased
linearly, the resistance of the vacuous medium in the tube
first increases with increasing current, only to
subsequently decrease, still with increasing applied
current, down to the minimum resistance value corresponding
to the sustaining potential of a "vacuum" arc (which is
somewhat above the ionization potential of the gas, or in
fact of the metal vapour, in the enclosure). As the
transition from a normal glow discharge into a "vacuum" arc
discharge is made either directly (in thermionic devices) or
indirectly, in cold-cathode conditions, via an abnormal glow
discharge that may be more or less precipitous, it is only
in the ideal diode and the ideal vacuum that both linear
functions (corresponding to the regimes that have a
sustaining potential) and nonlinear functions (corresponding
to the transition regions, such as the TRD and the AGD)
appear to depend exclusively upon the input current. In
fact, many factors affect the AGD, foremost amongst them,
pressure, plate distance and plate area. Hence the peak in
the curve of FIG. 1 is an idealized view of events.
Experimental observations show that
auto-electronic emissions characteristic of the pulsed
abnormal gas discharge (PAGD) regime emerge from the NGD, as
the current is increased beyond the point when the cathode
glow has reached plate saturation (if the current is not too
low and the plate area not too large).
The same effect occurs when the pressure is
reduced and the current is kept constant at a suitable level
(neither too high nor too low, exact figures depending on
other factors such as gap distance and plate area, etc.).
If the current is increased further, in either
case, the PAGD regime fully emerges (in other words, in
pumpdown tests, the applied current also has to be
sufficient). In this regime the plate is not so much
saturated with a negative glow (which remains, but is
attenuated), as it exhibits local concentrations of the
plasma that arise in a given area of the cathode as a
function of the auto-electronic emission mechanism. If the
applied current is increased in steps, a stage is reached at
which the extinction potential of the PAGD falls until it
meets the minimum potential of an arc discharge, as
demonstrated in FIG. 2. With reference to FIG. 1, this means
that the current-dependent variation of the PAGD in these
devices passes from a high to a low extinction potential or
from a high to a low electrical resistivity of the medium,
and is thus localized on the descending slope of the peak in
FIG. 1. Expressed in terms of resistance characteristics,
the regime of the pulsed abnormal glow discharge spans, as a
function of applied current, a subregion in which a positive
resistance characteristic changes into a leading negative
resistance characteristic. The pulsed regime of the AGD is
only sustainable when the intensity of the applied current
is greater than that needed to rapidly saturate the plates
(but not so great as to set up a VAD), the result being
development of auto-electronic emission with its associated
inverted cone-like discharge and a residual, faint glow of
the entire cathode (rather than a saturated glow discharge).
Each PAGD cycle begins as a singular emission
and performs a cycle of functions whose electrical
characteristics vary accordingly with time. During a
charging process (which eventually leads to emission), the
plate potential rises to a maximum at F (see FIG. 1), while
being limited by the maximum virtual value of the applied
current. Any substantial increase in the applied current is
blocked by the insulating properties of the intervening
medium (as if a very large resistance characterized the
device); in the discharge process, beginning with the
initiation of auto-electronic emission at F, conditions for
conduction across the (operational) vacuum are established
and, as a consequence, the resistance characteristic of the
device becomes increasingly negative until the extinction
potential is reached, at which point the glow discharge
ceases. This endogenous on/off behaviour is exactly what
characterizes the PAGD cycle.
Two boundary conditions arise. In the first
case, the available current is not quite enough to sustain
the PAGD. In this instance, full escape from the NGD regime
and the characteristics associated with its sustaining
potential will not occur, while any heating of the cathode
will eventually lead to the establishment of a
semi-thermionic cathode glow. In the second instance, there
is a risk of degeneration into a thermionic NGD or a VAD if
the available current is too high or sustained too long.
This degeneration will set in during the second phase of the
PAGD unit cycle, and may lower the resistance of the device
to the point of constant conduction of current across the
vacuum; the result is that the auto-electronic emission is
not quenched, as spontaneously happens in the PAGD.
Thereafter, extinction of the resulting VAD, which may be
promoted by a variety of factors is an unpredictable event;
if the current is available, the arc will burn for as long
as there is energy supplied and as long as there is cathode
material available to consume. A VAD in no way resembles a
regular, cyclic oscillator, which is the outstanding aspect
of the PAGD. Whilst an arc discharge is, like the PAGD, an
auto-electronic emission phenomenon characterized by
intermittences (the apparent constancy of an arc is the
result of the very high frequency of these intermittences),
such an arc does not exhibit the regular or quasi-regular
cyclical nature of the PAGD, nor its inherent current
limiting characteristics.
In order that a stable pulsed abnormal glow
discharge (PAGD) as discussed above may be obtained, the
discharge to be utilized must be capable of repeated
excursions into the region E to F of FIG. 1. This entails
that the tube be constructed so that, as the tube operates
and the current through it rises, the potential across the
tube can reach the peak F in FIG. 1 and beyond, without the
pulsed abnormal glow discharge degenerating into a vacuum
arc discharge. This will be influenced, among other factors,
by the extent of thermionic emission from the cathode which
will itself be influenced by resistive heating of the
electrodes and their work function, as well as by their
separation and configuration, and the nature and pressure of
gas within the tube, as well as the presence of auxiliary
electrodes or probes. The influence of these various factors
is extensively exemplified below. Whilst the present
invention is exemplified with reference to its
implementation using certain exemplary tubes, it should be
understood that the invention may be implemented utilizing
any tube capable of sustaining a stable PAGD discharge
without rapid self destruction whether or not of a structure
specifically disclosed. Thus we have been able to sustain
PAGD utilising tubes of diverse configuration; for example
high voltage thermionic diodes with the anode connected as
cathode, the cathode as anode, and the heater unused. Even
fluorescent lighting tubes can be operated briefly in the
PAGD regime although they are unsuitable for practical use
and fail very rapidly since their electrodes cannot
withstand the current densities involved. Even tubes having
electrode structures that can withstand the currents invoved
will not be suitable if they become heated to a point at
which thermionic emission promotes dgeneration of a PAGD
into a VAD.
FIGS. 3 through 5 of the drawings illustrate
the construction geometry of presently preferred embodiments
of tubes for use in pulse generators in accordance with the
invention. The discharge tubes are assembled using accepted
techniques which are well known to those skilled in the art
of vacuum tube technology.
FIG. 3 shows a discharge tube, generally
referred to by reference 50, having a cylindrical housing 52
which is preferably a glass material. Depending on the
interelectrode spacing of the discharge tube, which in
accordance with the invention may range from about 2 cm to
about 20 cm or more, the glass housing 52 is preferably
Pyrex (trademark), or #7740 borosilicate (Corning, N.Y.).
Such cylindrical housings 52 are commonly available in
diameters of about 6 to about 11 cm and a variable thickness
of about 0.2 to about 0.3 cm. Other borosilicate glass,
quartz glass or ceramic housings can be employed as suitable
alternatives to Pyrex glass and in sizes outside these
commonly available ranges.
The discharge tube 50 further includes two
parallel, spaced-apart electrodes comprising a cathode 54
and an anode 56, hereinafter often collectively referred to
as "plates" for brevity and convenience. As noted above, the
anode and cathode in discharge tubes according to the
invention are spaced 2 to 20 cm or more apart. The cathode
54 and the anode 56 may be either flat or curved and are
preferably made of 0.5 to 2.0 mm thick aluminum, nickel or
nickel alloy, zinc or iron. The thickness of the cathode 54
and the anode 56 is not critical and any thickness within a
reasonable range apparent to those skilled in the art may be
used. The surface areas of the cathode 54 and the anode 56
are preferably quite large in comparison to the surface area
of an anode/cathode in prior art vacuum tube devices.
Surface areas which range from 16 to 256 cm.sup.2 have been
tested, as described in the examples hereinafter. Although
the scope of the invention is not believed to be limited by
this range of surface area of values, it was generally
observed that the larger the surface area of the
anode/cathode tested, the more readily the discharge tube 50
elicited PAGD discharges providing other conditions such as
plate material, vacuum, residual gas fill, voltage and
current remained constant.
A preferred material for the cathode 54 and
the anode 56 is aluminum. Two specific types of aluminum are
preferred: namely, H34 rolled aluminum available from the
Alcan Company and Alzak (trademark) aluminum available from
the Alcoa company. Other types of aluminum are assumed to
constitute suitable material for cathode 54 and anode 56.
Aluminum is a preferred material because of its low work
function for field emission as well as for its other
qualities such as relative freedom from sputtering, except
when subjected to vacuum arc discharges, and its electrical
conductivity. In all instances, the aluminum used for
cathode 54 and anode 56 were degreased and rinsed in
accordance with published methods familiar to those skilled
in the art.
Each of the cathode 54 and anode 56 are
suspended within housing 52 by a support member 58 which
passes through hermetic seal 60 on opposite sides of the
housing 52. The support members 58 are preferably rigid rods
of substantially pure tungsten in a diameter of 1/16th to
3/32nds of an inch, or any suitable diameter. The material
of choice is round finished PureTung (trademark) available
from Union Carbide.
The discharge tube 50 also includes at least
one axial probe 62 and the discharge tube 50 shown in FIG. 3
has a tetrode geometry with two spaced-apart axial probes
62. Substantially pure tungsten rod is also the preferred
material for constructing the axial probe(s). All tungsten
rods used in assembling discharge tubes in accordance with
the invention were repeatedly cleaned with sodium nitrate
and fused with a beaded sleeve of uranium glass #3320
available from the Corning Company or Nonex (trademark)
glass #7720. These glasses are graded seals designed for
high vacuum tungsten/Pyrex junctions. Before the metal
components of the discharge tube 50 are introduced into the
glass housing 52, the housing is annealed at a temperature
of 565.degree. C. After the discharge tube was assembled, it
was connected by a glass constriction tube to the glass
manifold of a vacuum system (not illustrated).
FIG. 4 illustrates a further geometry for a
discharge tube 50 in accordance with the invention. The
discharge tube includes a parallelepiped shaped housing 64
which is assembled using a suitable plastic polymer sheet.
Polymer housings are preferably made from polycarbonate
resin, preferably ultraviolet resistant. The joints of the
rectangular panels are sealed for example with a low vapor
pressure resin Torr Seal (trademark) available from the
Varian Corporation which is applied along the mating edges
to glue the panels, or another adhesive system suitable for
withstanding the implosive forces of very high vacuum. For
very large housings 64 the walls are also preferably screwed
together at spaced-apart intervals. Non-metallic internal
braces can also be used to reinforce very large housings 64.
The polycarbonate housings are cleaned as per manufacturer's
instructions and all metal to polymer support interfaces,
such as the hermetic seals 60 where electrodes 58 and
probe(s) 62 pass through a side wall of the parallelepiped
shaped housing 64, are preferably epoxy resin joints made
with Torr Seal resin. The single axial probe 62 is made of
substantially pure tungsten rod.
FIG. 5 shows transverse cross-sections of
exemplary constructions of discharge tubes in accordance
with the invention. FIG. 5A illustrates a cylindrical
housing 52 with a flat plate anode 56 and cathode 54. As
shown in FIG. 5B, the anode 56 and the cathode 54 may be
elongated, transversely curved sections which are
substantially semi-cylindrical in shape. This anode/cathode
geometry is actually preferred for cylindrical housings. The
curved electrodes may be made from laser quality reflective
aluminum foil about 200 microns in thickness. Such
electrodes have a current tolerance of approximately 100 mA
of direct current in the PAGD regime and are easily
destroyed by current induced disruptive slippage into arc
discharge. Curved electrodes of press-formed aluminum plate
are therefore preferred over curved electrodes made from
aluminum foil.
Processing of the Vacua
An oil diffusion/rotary pump combination
(EO2/E2M2, Edwards High-vacuum, using Silicone 705 diffusion
oil), equipped with thermocouple and Penning gauges (for
rotary and diffusion vacua, respectively), was used to
pumpdown a large bore glass-metal vacuum system equipped
with a baffle valve, desiccating and cold traps, down to
10.sup..about.7 Torr (=mm Hg) pressures. At 10.sup.-3 to
10.sup.-4 Torr, the rotary pump was bypassed, and 500 mm Hg
of UHP (ultra high purity, spectroscopic grade 99.9996%
pure) argon was admitted into the system. The system was
then evacuated back to 10.sup.-4 Torr and the operation was
repeated three more times except the third time a tension of
25 kV (10 mA) DC was applied to the plate electrodes when
the pressure reached .sup.- 10 mm Hg. Cold cathode normal
glow discharge (NGD) currents of 10 mA were used to liberate
all adsorbed gases remaining in the electrodes and the inner
face of the housing (52,64), while the pressure fell to
10.sup.-4 Torr. Flame heating of the housing 52 was also
performed throughout and most intensely at the constriction
joint. Two external, water-cooled copper RF coils were then
applied at each end of the housing 52 and operated at 450
KHz, at calibrated temperatures of 400.degree. C. to further
facilitate the liberation of occluded gases, excessive
heating being strictly avoided. Alternatively to the RF
induction heater, an electrical tape (eg. Briskheat
(trademark)) controlled at a temperature of 400.degree. C.
can be applied to the glass housing. After about 30 minutes,
the RF induction heater was turned off and a 100 Kc 30 kV
Tesla coil was applied unipolarly to the probe(s). Then,
once more, 500 mm Hg of UHP argon were admitted into the
system and the cycle of evacuation, heating and bombardment
was repeated, except this time the diffusion pump was
connected to the system and the electron bombardment was
carried out to pressures of 5*10.sup.-5 Torr. At this point,
and with the 25 kV DC still on, weak x-ray production
occurred at the plate edges and this could be detected with
a sensitive, mica-window Geiger-Muller tube counter set at a
5 cm distance from the discharge tube housing 52, 64. This
x-ray production can be sustained indefinitely at these
kilovoltages and at a pressure of 10.sup.-6 Torr, without
degenerating into a glow discharge (ie. without evolution of
gas and a rise in pressure). The tube was then considered to
be practically clean (`hard` or x-ray vacuum). It was then
pumped down to the 10.sup.-7 Torr range until all discharge
ceased and maintained at that vacuum for a further 8 hrs.
Seal-off at the constriction joint involved slowly heating
the joint such that the pressure never rose above 10.sup.-6
Torr. The end-processed discharge tubes 50 were all closed
at different values of `hard` vacua (10.sup.-6 Torr or
higher vacua). For discharge tubes 50 closed at lower vacua
(medium vacuum), ie. at pressures higher than 10.sup.-6 Torr
but lower than 10.sup.-4 Torr, the desired pressure was
achieved by reintroducing controlled amounts of UHP argon
and adjusting with the diffusion pump on, after thorough
processing, as described above. For discharge tubes 50
closed at low vacuum to medium vacuum (5 to 10.sup.-4 Torr),
the diffusion pump did not need to be turned on and the
procedures of heating and electron bombardment were followed
at the maximal rotary pump vacuum of .sup.- 7.5 to
5*10.sup.-4 Torr. The desired final pressure was achieved by
an identically controlled re-admission of small quantities
of UHP argon.
Discharge tubes 50 built with polymer-type
housings 64 cannot withstand the heating step during
pumpdown (nor do they require annealing). Accordingly, only
the electron bombardment procedure was performed while
processing the vacuum for those discharge tubes, and for
suitably longer periods (up to 1 hour each cycle). Pumpdown
times were also extended under those conditions.
During and after vacuum processing, the vacua
were constantly tested at the electrodes and at the probes
with a unipolar 30 kV Tesla coil, when all other electrical
apparatus were off. At pressures near 10.sup.-4 Torr only a
faint local bluish fluorescence could be detected, and at
pressures greater than 5*10.sup.-5 Torr no discharge could
be observed (so-called `black` vacuum).
The following examples of tests conducted with
pulse generators incorporating discharge tubes 50 illustrate
the character and performance of such pulse generators. The
disharge tubes utilised are listed in Table 1.
For test purposes, the tubes were utilised in
test circuits as shown in FIGS. 20A and 20B. The circuit of
FIG. 20A was used for most tests, the additional features of
FIG. 20B being used only for the tests described with
reference to FIGS. 16-18.
In FIG. 20A, a low impedance DC power supply
PS had terminals connected to plate electrodes of a
discharge tube 50, in the case of a first terminal through a
ballast resistor R, of a resistance which is selected
according to the test being performed, and an ammeter
capable of measuring DC current or RMS AC current. The other
terminal was grounded. A DC voltmeter was connected across
the tube 50, and a probe electrode of the tube 50 was left
unconnected.
TABLE
1
______________________________________
List of all the devices utilized
Plate
Vacuum
# Area, cm.sup.2
material
d, cm in Torr
FIG.S
______________________________________
1
128 H34 Al.
5 10.sup.-6
5,
6, 7, 8, 9,
18,
19
2
128
Alzak 5 10.sup.-6
8
3
16 H34 Al.
5.5 Variable
11,
12, 14
4
64 H34 Al.
5.5 Variable
11,
12
5
128 H34 Al.
5.5 Variable
11,
12, 13
6
128 H34 Al.
5.5 Variable
11
7
16 H34 Al.
5.0 2 * 10.sup.-6
16,
17
8
16 H34 Al.
5.0 2 * 10.sup.-6
16
9
64 H34 Al.
5.0 2 * 10.sup.-6
16,
17
10
64 H34 Al.
5.0 2 * 10.sup.-6
16
11
128 H34 Al.
5.0 2 * 10.sup.-6
16,
17
12
128 H34 Al.
5.0 2 * 10.sup.-6
16
13
256 H34 Al.
5.0 2 * 10.sup.-6
16,
17
14
64
Alzak 5.0 2 * 10.sup.-6
17
15
77
Alzak 5.0 2 * 10.sup.-6
17
16
128
Alzak 5.0 2 * 10.sup.-6
17
17
64
H34 3.6 2 *
10.sup.-6
(Table
5)
______________________________________
In FIG. 20B, the first terminal was grounded
so that a current waveform developed across the ballast
resistor R could be monitored by an oscilloscope OSC1,
voltage variations across the tube being monitored by the
oscilloscope OSC1 through a capacitor C1. The potential at
the probe electrode was monitored through a further
capacitor C2 by a further oscilloscope OSC2.
It should be understood that the above
circuits are designed for the purpose of testing the
invention, and in many practical applications of the pulse
generator of the invention, it will be necessary to couple
the plate electrodes to a further circuit arm driven by the
pulse generator, the coupling typically utilising capacitors
and/or diodes. The real and imaginary components of any load
applied through such a coupling will influence the operating
conditions of the pulse generator, and it may also be
necessary to include diodes in series with the connections
to the power supply as shown in FIGS. 21A & B in order
to help isolate the load from the supply, thus turning the
pulse generator into a double ported device.
EXAMPLE 1
Volt-ampere Characteristics of a Pulse
Generator
The tests described in this example were
conducted with a discharge tube 50 (device #1) constructed
with H34 aluminum flat plates (128 cm.sup.2 area) set 5 cm
apart, and equidistantly from a continuous axial probe 62 in
a vacuum which measured 10.sup.-6 Torr at time of seal off.
FIG. 2 shows that under conditions of a positive, constant
DC voltage applied to the anode 56 of this device, the
volt-ampere curve for both breakdown potential (Vb, shown as
open squares) and for the minimum discharge potentials (Vs,
or VAD sustaining potential and Vx, or extinction PAGD
potential, both shown as closed circles) disclose two
regions or regimes in the operation of this device, a region
of pulsed AGD which spanned from about 10 mA to about 150 mA
RMS (with an applied maximum of 15 mA DC average), and a
region of VAD at RMS current values greater than 250 mA.
PAGD current data was derived from peak pulse RMS values and
VAD RMS current data was obtained at steady-state. Within
the range of the pulsed AGD, the Vb values were high and
plateaued at about 850 volts; Vb values for the VAD regime
were generally lower than those of the PAGD and could be
raised by an increase in available current.
As shown in FIG. 6, a PAGD regime could also
be equally identified when the supplied DC voltage was
negative and applied to the same cathode plate 54 (see FIG.
3), for both PAGD and VAD, Vb and Vx values (closed and open
squares, respectively) at comparable transduced pulse RMS
currents. Utilizing a 10-fold higher direct current power
supply, also earth-grounded at the centertap but having a
parallel supply capacitance of 55 mfd and a slow voltage
recovery rate (ie. less than 200 V/sec), the same discharge
tube 50 (device #1) yielded 10.times. higher peak PAGD RMS
currents (2 A vs. 200 mA) than were obtained under the same
conditions and with the same power supply by a positive
applied voltage of equal magnitude. These findings suggest
that, at high applied direct currents, there is a strong
asymmetric response of the discharge tubes 50 (larger PAGD
RMS current values with cathodic tension than with
comparable anodic tension) with respect to the sign of the
plate polarization in reference to earth-ground.
It is also apparent that the field emission
responsible for the PAGD regime does not obey the
Fowler-Nordheim VAD region law (see FIG. 7): whereas the VAD
graph has the expected negative slope, the slope of the PAGD
graph is positive, contrary to predictions by the
Fowler-Nordheim VAD region law. This constitutes strong
evidence for the existence of auto-electronic emission
discharges that occur at much lower input currents than
predicted by the Fowler-Nordheim field-emission theory.
EXAMPLE 2
Pulse Count Rates in the PAGD Region
Two pulse count studies were done: a first at
low applied direct currents (<1.5 mA) and a second at mid
to high applied direct currents (1.5 mA to 200 mA). Peak
pulse RMS currents during the second study were as high as 2
A. Two tubes were used, each having 128 cm.sup.2 rigid, flat
plate anode/cathode set 5 cm apart, a continual axial probe
and a 10.sup.-6 Torr vacua at time of manufacture, but
having different plate materials; namely H34 aluminum
(device #1) and Alzak (trademark) aluminum (device #2)
respectively; the applied direct currents were increased
with the voltage from 0.1 to 1.0 mA, and all measurements
were taken with a 1 Mohm ballast resistor.
At low currents (see FIG. 8), using the
discharge tube 50 (device #1) assembled with H34 aluminum
plates and ballasted with a 1 Mohm resistor and a lower
pulse amplitude detection cut-off at less than 25 V, the
pulse per minute counts at the axial probe were observed to
increase as the anode-supplied voltage (and the current, not
illustrated), was incremented from 300 V to 500 V. At higher
voltages, the pulse count plateaued at a somewhat depressed
level (FIG. 8, open squares). Conversely, utilizing a
discharge tube (device #2) assembled with Alzak plates in an
identical vacuum at seal off (10.sup.-6 Torr), the pulse
counts increased with applied voltage up to a maximum
voltage applied, the maximum pulse count being about 9 times
higher than observed with device #1 (FIG. 8, closed
circles). Reducing the ballast resistance increased the
pulse rate of device #1 to a maximum of 1000 pps or 60,000
PPM with a 0.125 ohm resistor, and increased the pulse rate
of device #2 to 4000 pps or 240,000 PPM. Analysis of the
pulse signals with an oscilloscope showed that, in both
instances, the observed CPM (counts per minute) values at
the axial probe 62 effectively corresponded (about 1:1) to
the PPM (pulses per minute) values at the cathode 54, under
these conditions, for both devices #1 and #2.
At currents higher than 1.0 mA, when the PAGD
regime is fully active, the inverse phenomenon was observed:
ie. the pulse rates increased with a decrease in the value
of the extinction voltage (Vx) (see FIG. 9). FIG. 9
illustrates the continuous variation of the pulse per minute
rate as a function of anode-supplied (open squares) or
cathode-supplied (open circles) DC voltage, at applied
currents that varied from 1 to 200 mA (the higher current
sequence for the anode voltage is on the left); the anode
voltage curve shown on the right side of the figure was
obtained using an intermediate current supply; the two other
slopes were obtained using a high current supply;
capacitance values for both high and intermediate current
supplies were respectively, 50 and 1 mfd, both power
supplies being earth-grounded; the discharge tube (device
#1) had 128 cm.sup.2 H34 aluminum plates set 5 cm apart and
enclosed a vacuum measured at 10.sup.-6 Torr at time of seal
off.
Pulse rates also increased proportionally to
the transduced pulse RMS current (see FIG. 10). FIG. 10
illustrates an increase in the pulse frequency per minute as
a function of the peak pulse RMS current, at applied
currents from 1 to 200 mA; corresponding voltages are shown
in FIG. 9 (not for all points) and the higher current,
anode-supplied curve corresponds to the lower voltage curve
in FIG. 9, all conditions being as described for FIG. 9. The
pulse rate increase was observed for both positive and
negative polarizations (squares and circles, respectively,
in both FIGS. 9 and 10) of the `vacuum`, with discharge tube
50 (device #1). Under these conditions and with a 1 Mohm
ballast resistor, rates of 113-124 pps were measured, the
limiting factor being the recovery time of the voltage
regulation of the power supply as the current drain
increased. This phenomenon was exaggerated when no ballast
was employed and the largest peak pulse currents were
observed (not shown). With faster recovery power supplies
capable of delivering the same or higher input currents (and
the same large value of capacitance in parallel with the
plates) much higher pulse rates (>1,000 pps) could be
obtained, along with larger peak pulse RMS currents.
EXAMPLE 3
Detection of the PAGD Region in the Pulse
Generator as a Function of Decreasing Pressure
Argon pumpdown tests were conducted to
determine whether and when the PAGD region of the discharge
was apparent utilizing comparably low voltages (up to 2.5
kV). These tests were performed with both the diffusion pump
off and on. FIG. 11 shows a typical curve of the variation
of the sustaining/extinction voltages at the plates with
decreasing pressure at the rotary pump, from breakdown (at
860 VDC) to glow extinction, for all four discharge tubes 50
examined (device #'s 3 to 6), which were assembled with H34
aluminum plates having different electrode areas: device #3,
16 cm.sup.2 (small closed squares); device #4, 64 cm.sup.2
(open circles); device #5, 128 cm.sup.2 (open squares);
device #6, 128 cm.sup.2 (large closed squares). Each
discharge tube 50 had the same gap distance of 5.5 cm and
was assembled with the same volume of glass envelope.
Devices #3 to 5 were evacuated simultaneously and an
identical average direct current of 1 mA was applied to each
separately, using comparable power supplies ballasted with a
1 Mohm resistor. Device #6 was evacuated in a separate test,
under the same pumpdown conditions and at the same applied
potential of 860 VDC at breakdown, but was subjected to a
100-fold higher, average direct current of 500 mA. It is
readily apparent that the continuously varying,
sustaining/extinction voltage curves shown in FIG. 11 are
analogous to the Paschen gas breakdown voltage curve and
that throughout most of the voltage range all three low
current curves are parallel. Independent determinations of
the low current breakdown voltage curves for all three
discharge tubes 50 (devices #3 to 5) showed the exact same
relation for all three curves as observed for the
sustaining/extinction voltage curves (results not shown).
The differences between the electrical discharge regimes
observed as a function of decreasing pressure are most
apparent in the larger plate area discharge tube 50 (device
#5). The three regions of the discharge, the transitional
glow, the normal glow and the pulsed abnormal glow, are
clearly distinguishable for that device (see FIG. 11). FIG.
11 illustrates a continuous variation of NGD sustaining/PAGD
extinction voltages (Vs/Vx), from breakdown to glow
extinction, with decreasing pressure (at a rotary pump), in
4 discharge tubes having different plate areas but the same
electrode material (H34 aluminum), the same gap distance and
the same potential of 860 VDC prior to breakdown; all curves
except that joining the large closed squares, were measured
using the same low applied direct current of 1 mA; the curve
joining the large closed squares was obtained with an
average direct current of 500 mA; the three quasi-parallel,
low current curves for discharge tubes (devices #3 to #5)
having anode/cathode areas of 16 (small closed squares), 64
(open circles) and 128 cm.sup.2 (open squares),
respectively, were obtained during a simultaneous test; the
high-current curve for a 128 cm.sup.2 plate discharge tube
(device #6) was measured during a separate test. In all
cases, pumpdown was performed in an argon atmosphere. The
scale markings for different glow discharge regions shown at
the upper part of the diagram refers only to observations
made with a 128 cm.sup.2 area discharge tube device #5 at
low applied currents. In the transitional region discharge
(TRD), the cathode glow is of minimal point-like size and
rapid oscillations of the striations of the plasma positive
column originate quasi-sinusoidal, dampened sinusoids,
ramp-like or noise-like waveforms associated with sporadic,
small amplitude (2 to 15 volts), pulsed auto-electronic
emissions. In this region the voltage tends to fall, while
oscillating erratically at first. As the pressure further
decreases, there follows a stable normal glow discharge
(NGD) region, where conduction of direct current across the
vacuum pre-empts the possibility of auto-electronic
emission. The lowest voltages are observed in this region.
After the recession of the positive column and upon glow
saturation of the plate areas, just as the cathode glow is
beginning to recede, the intense, large amplitude (>100
V), pulsed auto-electronic emission characteristic of the
PAGD regime emerges. In this region, the voltage tends to
climb until extinction occurs before the maximum voltage of
860 V is again attained. In the other two devices at the
same low applied direct current, the borders of the
discharge regimes are blurred. In device #3, the low
intensity, small amplitude auto-electronic emissions develop
into a few high intensity, large amplitude emissions, as
they decrease in frequency and with considerable overlap;
the PAGD and NGD regimes are also mostly mixed, until lower
pressures of the order of 0.01 Torr are attained, at which
point the PAGD regime functions alone at low frequency. In
device #4, the NGD regime can be better distinguished from
the TRD, and the PAGD from the NGD, but high intensity,
large amplitude auto-electronic emissions occur early on in
the NGD region as the glow saturates the plates faster than
for device #5. There is a dual effect on increasing the
average applied direct current 100-fold (device #6, large
closed squares, shown in FIG. 11): the entire ascending arm
of the voltage curve is displaced upward in the pressure
scale and the modal distribution of the voltage variation is
compressed. The high applied direct current also abrogates
the two discharge regions that preceded the PAGD. From
breakdown to extinction, the regime of the discharge is
solely that of the PAGD, the positive column of the
discharge weakening with the decreasing pressure.
FIG. 12 illustrates a continuous variation of
PAGD frequency with decreasing gas pressure in 3 discharge
tubes having different anode and cathode plate areas (16,
64, 128 cm.sup.2) but the same cathode material (H34
aluminum) and the same gap distance of 5.5 cm; all 3
discharge tubes (device #'s 3 to 5) were applied the same
potential of 860 VDC prior to breakdown and were stimulated
with the same direct current of 1 mA; pumpdown was performed
with a rotary vacuum pump in an argon atmosphere; neither
the quasi-sinusoidal nor the noise-like oscillations
observed upon breakdown and during the transitional
discharge region, nor the low intensity auto-electronic
pulsed emission (2 to 15 v maximum amplitude) observed in
the same region, are shown. In all three devices, the PAGD
regime first appeared mixed together with the NGD regime in
the form of pulses that perturbed the steady-state glow, the
pulses increasing in frequency with the decreasing pressure
until a maximum pulse rate was attained.
FIG. 13 illustrates a shift of the PAGD regime
to higher pressure regions during pumpdown with a rotary
vacuum pump in an argon atmosphere, as a function of a
500-fold increase in applied direct current (1 vs. 500 mA),
at the same starting voltage of 860 VDC and utilizing the
same 128 cm.sup.2 H34 aluminum plate discharge tube (device
#5) in two separate tests. The higher current displaces the
PAGD region upward in the pressure scale, just as was
observed in the ascending arm of the voltage curve (see FIG.
11). The displacement induced by the applied high current
occurs over a pressure range where, at low current (1 mA)
and with the same applied potential at breakdown, some weak,
low-amplitude, pulsed auto-electronic emissions are observed
during the TRD.
FIG. 14 illustrates a shift of the PAGD regime
to lower pressure regions and higher frequencies during
pumpdown with a rotary vacuum pump in an argon atmosphere,
as a function of a higher applied potential; starting
voltages were 860 (closed squares) and 1500 VDC (open
squares). The discharge tube (device #3) had plate areas of
16 cm.sup.2 and the results shown are from separate tests
with the same power supply, at low currents (average 1 mA).
FIG. 14 shows the effect of increasing the starting DC
voltage at breakdown by 1.75-fold (from 860 to 1507 VDC).
The increased current displaced the PAGD upper pressure
limit downward in the pressure scale, in opposition to the
current effect and it also increased by a factor of about
8.8 the frequency of the intense, large amplitude,
auto-electronic emissions.
Using the same applied low direct current and
potential magnitude at breakdown (860 VDC) described for the
tests represented in FIGS. 11 and 12, pumpdown of the three
different plate area discharge tubes 50 (each having
interelectrode distances of 5.5 cm) was performed with the
oil diffusion pump on. While the effect of increasing the
plate area under these conditions remained the same, ie.
lowering the pressure for the same sustaining/extinction
potential and displacing the PAGD region to regions of
higher vacuum, there was a noticeable difference compared
with the same test done with the rotary pumpdown: ie. the
extinction pressure was greatly extended downward in the
pressure scale for all devices, and, consequently, the PAGD
region was greatly expanded into the medium to high vacuum
ranges. A 128 cm.sup.2 plate area discharge tube 50 with 5.5
cm gap, (devices #11 and 12) typically reached PAGD
extinction at 5*10.sup.-5 Torr, though its peak pulse rate
remained basically unchanged. This overall displacement of
the PAGD phenomenon to higher vacuum regions under
conditions of oil diffusion evacuation may well be due to
the migration of very low vapor pressure oil molecules to
the tube ends (despite the baffle and the cooling trap) and
their interaction with residual gas molecules in the
electrical field of the devices. With the diffusion pump on
and voltages progressively increasing up to 2.5 kV with
decreasing pressure, the PAGD regime in these discharge
tubes 50 operated from 10.sup.-3 to 10.sup.-5 Torr.
Typically a 128 cm.sup.2 H34 aluminum plate discharge tube
50 (5.5 cm gap) will operate in the PAGD regime at
2*10.sup.-5 Torr, with an applied voltage of 2.2 kV and at a
pulse rate of 30 pps. With higher vacua (<10.sup.-5 Torr)
and voltages, ultimately the PAGD regime gives way to the
production of cathode rays and very weak x-rays. From
several such diffusion pumpdown tests it was concluded that
the PAGD was facilitated by the use of Alzak electrode
material and, as it will be shown in Example 4, by larger
plate areas.
EXAMPLE 4
The Effect of the Plate Area on the PAGD
Characteristics During Pumpdown
The effect of increasing the plate area of the
cathode 54 and anode 56 of a discharge tube 50 was tested by
two methods: 1) using a pumpdown method of varying the
vacuum by equilibrating of the gas flow against a rotary
pump (as explained below) and 2) using sealed housings 52,
64 enclosing a vacuum of 2*10.sup.-6 Torr obtained with the
diffusion pump (see Example 5).
The results from the first test is shown in
FIGS. 11 and 12, for the discharge tubes 50 stimulated with
low (1 mA) direct currents, at the same starting potential
of 860 VDC at breakdown. A comparison indicates that the
effect of increasing the plate area in discharge tubes 50
having the same gap distance, and thus the same pd value
(pressure, in Torr, multiplied by interelectrode gap
distance, in cm), and the same volume, is to depress the
voltage, particularly in the NGD and PAGD regions and to
displace the auto-electronic pulsed emission characteristic
of the PAGD regime to a higher vacuum range. The peak
frequency of PAGD for each given area is also attained, in
each case, at a vacuum that increases proportionately to the
order of increasing area (16.fwdarw.64.fwdarw.128 cm.sup.2)
as does the magnitude of the peak frequency of PAGD for a
given gap distance. The distribution of PAGD frequencies
also narrows its characteristic mode with the larger area
plates, by displacing an upper pressure limit to lower
pressure regions, the most significant shift in this respect
being from the 64 to the 128 cm.sup.2 devices (FIG. 12, open
circles vs. open squares). This combined compression of the
distribution mode and its shift to the left in the pressure
scale corresponds to a better definition between the NGD and
the PAGD regimes afforded by the discharge tube 50 with the
largest plate area employed (128 cm.sup.2), as discussed
above in Example 3. Moreover, in accordance with Paschen's
law, the observed area-dependent voltage reduction effect
cannot be explained, inasmuch as the voltage is predicted to
remain the same as long as the product pd is constant, even
if the plate area increases. Since the interelectrode gap
distance was constant for all devices and as the pumpdown
was also performed simultaneously and the tubes had
identical volumes, it is apparent that there is an electrode
plate area effect which is not accounted for by Paschen's
law. The observed plate area effect appeared to have an
effect opposite to current and in the same direction of
increasing potential, as it displaced the PAGD region
downward in the pressure scale to higher vacuum regionsand
increased the PAGD frequency. In addition, an increase in
area also reduces the magnitude of the potential. From the
results shown in FIG. 14, and a comparison with FIG. 12, it
is apparent that an increase of 1.75-fold for a given
breakdown potential of a 16 cm.sup.2 discharge tube yields
the same pulse rate (about 60 pps) as does an 8-fold
increase in plate area for the same volume housing (52, 64),
but requires a lower pressure.
A comparison of breakdown order and pressure,
as well as of peak pps values and peak pps conditions
carried out as a function of plate area for the discharge
tubes 50 (devices #'s 3 to 5) represented in FIGS. 11 and
12, is shown in Table 2. The discharge tube 50 with the
largest plate area, which was the first to undergo breakdown
(during six separate tests) at the highest pressure of 3
Torr, yields an 8-fold higher PAGD rate than the discharge
tube 50 with the smallest plate area of 16 cm.sup.2, at the
lowest pressure (the pressure is 24 times lower than that of
the 16 cm.sup.2 device). This peak pps rate occurs, however,
at a voltage which is about 9.5% greater for the discharge
tube 50 with the largest plate area. These results suggest
that a larger plate area promotes breakdown at higher
pressures (ie. the breakdown pressure decreases inversely to
the order of increasing plate area) and supports lower
sustaining/extinction voltages.
Tables 3 and 4 list sampled data from the
tests shown in FIGS. 11 and 12. Table 3 shows a comparison,
by fixed voltages, of values on the ascending arm of
pressure dependent voltage curves for three discharge tubes
50 having different plate areas. Table 4 shows the pressure
variation predicted by the Paschen law if the devices had an
interelectrode gap that varied proportionally to a linear
scaling factor k.sub.L (which they do not) and a pressure
that varied inversely to the linear scaling factor k.sub.L.
In both Tables 3 and 4 the first six vertical columns
describe (1) the plate area values of the three discharge
tubes 50 tested, (2) the linear scaling factors k.sub.L for
each discharge tube 50 based exclusively on the linear plate
dimensions (ie. not implying a k.sub.L scaled gap distance),
(3) their respective area scaling factors (k.sub.A), (4) the
interelectrode gap distances in cm, (5) the pressure in Torr
and (6) the DC voltage.
Table 3 is horizontally divided into two
parts. Groups A and B represent two sets of theoretical
predictions derived from the Paschen law and in conformity
with the Child-Langmuir theory of the NGD.
Group A represents the model for a linear
scaling of all dimensions, as when the plate factor k.sub.L
also applies to the distance between the plates, which thus
must increase by the k.sub.L value. This requires that for
the voltage to remain unchanged, the pressure must decrease
by the reciprocal of the k.sub.L value. Accordingly, a
theoretical pressure reduction factor (prf) is shown in
vertical column 8 of Table 3, and the predicted pressure
values shown in vertical column 5.
Since in group B, the k.sub.L scaling factor
does not apply to the gap distance, which thus remains
constant at 5.5 cm, the theoretical prf is unity and the
pressure remains constant if the voltage is to remain the
same.
For the horizontal sample groups numbered 1 to
6, column 5 shows the experimental pressure values obtained
for the same sample voltage and column 8 shows the observed
prf values. Column 7 shows the experimental pps rates. It is
readily apparent from the experimental values of Table 3,
that identical voltages entail reduced pressures that
diminish as an area dependent effect. Contrary to the
prediction (group B, Table 3), and despite the fact that the
interelectrode gap distance remains the same for all the
discharge tubes 50 (device #'s 3 to 5), a constant voltage
is only attained at a lower pressure for the discharge tubes
50 with larger plate areas. In other words, the product pd
is not constant for a given voltage, and thus does not
conform to the Paschen Law prediction of a prf that equals
unity for all discharge tubes 50 regardless of their plate
area.
In Table 4 only experimental data is
presented. The predicted voltages shown in vertical column 6
of Table 4, were obtained using as parameter the
experimental values observed for the discharge tube 50 with
the smallest area (16 cm.sup.2) used in these tests, at
pressure intervals determined from arbitrary prf factors
(vertical column 9, Table 4) chosen in accordance with a
theoretical model of the horizontal group A from Table 3,
that is, as if the reciprocal of the k.sub.L factor applied
to the pressure of these discharge tubes, even though the
interelectrode gap remained constant. Using those pressure
intervals, and the actual voltages observed for the other
two discharge tubes (64 cm.sup.2 and 128 cm.sup.2, vertical
column 7, Table 4), the experimentally observed voltage
reductions as % of the 16 cm.sup.2 voltage reference (shown
in column 6) were determined and are shown in vertical
column 10, Table 4.
The experimental data listed in Tables 3 and 4
was then used to calculate relative, average pressure
reduction factors using the fixed voltage series shown in
Table 3, column 8, and percentage voltage reductions using
the 1/k.sub.L pressure series shown in Table 4, column 10.
Those calculations interrelated all the discharge tubes used
for the low current pumpdown test with respect to their
plate area factors, or k.sub.A values: ie. k.sub.A =2, when
comparing the 64 cm.sup.2 and 128 cm.sup.2 discharge tubes;
k.sub.A =4, when comparing the 16 cm.sup.2 and the 64
cm.sup.2 discharge tubes; and k.sub.A =8, when comparing the
16 cm.sup.2 and 128 cm.sup.2 discharge tubes. To triangulate
the data, k.sub.A =8 results for the voltage series of Table
5 were derived by comparing the pressures obtained for the
16 cm.sup.2 and 128 cm.sup.2 discharge tubes, shown in Table
1. With respect to the pressure series of Table 5, whereas
the 16 cm.sup.2 device was used as a 100% voltage reference
for the k.sub.A =4 and k.sub.A =8 results, the k.sub.A =2
results were determined by comparing the percentage voltage
reduction for the 64 cm.sup.2 and 128 cm.sup.2 devices. From
the triangulated data, statistical means and their standard
errors were calculated to determine the regression curves of
the area dependent pressure reduction effect obtained when
the voltage is constant (FIG. 15A), and of the
area-dependent voltage reduction as % of the maximum, when
the voltage of the 16 cm.sup.2 discharge tube is taken as a
reference voltage and the pressure is varied arbitrarily in
accordance to the reciprocal of the k.sub.L factor(FIG.
15B). FIGS. 15A and 15B strikingly illustrate the effect of
increasing the k.sub.A factor or the plate area in these
discharge tubes 50. A lower pressure is required for the
same voltage (ie. a prf lower than unity), the voltage being
depressed when the pressure is constant. Within the k.sub.A
range tested, both regression curves are linear. Following
the regression curve of FIG. 15A, one can predict that a
k.sub.A =17 will reduce the pressure by one order of
magnitude. Conversely, following the regression curve of
FIG. 15B, one can predict that for the same pressure and the
same interelectrode gap distance, the voltage will be
depressed by 50% with a k.sub.A =.sup..about. 21.5. These
predictions, however, will only hold if the curve remains
linear throughout a wider range of k.sub.A values.
In conclusion, the effect of increasing the
plate area of discharge tubes stimulated with the same
starting voltage and the same current is to: 1) shift the
breakdown pressure upwards, 2) depress the working voltage,
3) increase the pulse rate both in the TRD and PAGD regions,
4) shift the PAGD region downwards in the pressure scale and
segregate the discharge regimes more clearly as a function
of decreasing pressure. These observations also explain why
the discharge tubes with smaller plate areas shift the PAGD
up in the pressure scale, as an increase in current does.
Effectively, a smaller plate area not only concentrates the
lines of electrostatic force in a vacuum, but it also
increases the current density per unit area, with the
consequent glow saturation of the plates, necessary for the
abnormal glow discharge region to be attained, occurring
earlier on during pumpdown, than for discharge tubes with
larger plate areas.
TABLE
2
______________________________________
Plate Area
16
64 128
(cm.sup.2)
Lowest DC Voltage
290
226
210
(5mA current)
Pressure
0.31
0.68 0.415
(Torr)
Expected Breakdown
2.25
2.25
2.25
Pressure
Breakdown Pressure
0.75
0.83
1
Factor
Breakdown Order
2.7
.+-. 0.37
2
.+-. 0.29
1.3
.+-. 0.23
M .+-. SEM (n = 6)
Peak PPS
7
16 61
Relative PPS Ratios
1
2.29
8x
1
3.5x
Peak PPS Pressure
0.725
0.220 0.030
Peak PPS Volts DC
307
225
332
______________________________________
TABLE
3
______________________________________
Pre-
dicted
Theoreti-
Area
Plate
d,
p
cal
(cm.sup.2)
K.sub.L
K.sub.A
cm
(Torr)
V
PPS prf Group
______________________________________
16
1 1
5.5 0.125 307 NA
NA A
64
2 4
11 0.0625
307
NA 1/K.sub.L =
A
1/2
128 1.4
2 15.5 0.044 307
NA 1/K.sub.L =
A
1/1.4
16
1 1
5.5 0.125 307 NA
NA B
64
2 4
5.5 0.125 307 NA
1 B
128 1.41
2 5.5 0.125 307
NA 1 B
______________________________________
Sam-
Area
Plate
d, Exptl.
p
ple
(cm.sup.2)
K.sub.L
K.sub.A
cm
(Torr) V PPS Exptl.prf
#
______________________________________
16
1 1
5.5 NA 255
NA NA 1
64
2 4
5.5 0.18 255 14
NA 1
128 1.41
2 5.5 0.092 255
1 1/1.96 1
16
1 1
5.5 0.125 307 4
NA 2
64
2 4
5.5 0.065 307 5 1/1.91 2
128 1.41
2 5.5 0.035 307
36 1/1.86 2
16
1 1
5.5 0.0675 350 2.5
NA 3
64
2 4
5.5 0.0475 350 4.5 1/1.42 3
128 1.41
2 5.5 0.023 350
56 1/2 3
16
1 1
5.5 0.0500 407 2
NA 4
64
2 4
5.5 0.0225 407 2.5 1/2 4
128 1.41
2 5.5 0.0090 407
30 1/2 4
16
1 1
5.5 0.0310 450 0.8
NA 5
64
2 4
5.5 0.0091 450 1.5 1/3 5
128 1.41
2 5.5 0.0060 450
22 1/1.52 5
16
1 1
5.5 0.0140 500 0.65 NA 6
64
2 4
5.5 0.0060 500 1.2 1/2 6
128 1.41
2 5.5 0.0038 500
5 1/1.58 6
______________________________________
TABLE
4
__________________________________________________________________________
Voltage
Area
Plate
d
p V
V Chosen p
Reduction
Sample
(cm.sup.2)
K.sub.L
K.sub.A
(cm)
(Torr)
Predicted
Observed
PPS
Factor
as
% #
__________________________________________________________________________
16 1 1 5.5
0.800
318
318 4 NA NA = 1
100%
64 2 4 5.5
0.400
291
253 10 1/2 86.94 1
128 1.41
2 5.5
0.2283
290
250 0 1/1.42
86.2
1
16 1 1 5.5
0.400
291
291 5 NA NA 2
64 2 4 5.5
0.200
295
257 15 1/2 87.1 2
128 1.41
2 5.5
0.141
309
243 0 1/1.41
78.6
2
16 1 1 5.5
0.200
295
295 4 NA NA 3
64 2 4 5.5
0.100
327
260 6.5
1/2
79.5 3
128 1.41
2 5.5
0.070
350
265 9.5
1/1.41
75.7
3
16 1 1 5.5
0.0800
334
334 3 NA NA 4
64 2 4 5.5
0.0400
422
365 4.25
1/2
86.5 4
128 1.41
2 5.5
0.0283
457
347 58 1/1.41
75.9
4
16 1 1 5.5
0.0400
422
422 1.5
NA
NA 5
64 2 4 5.5
0.0200
473
415 1.8
1/2
87.7 5
128 1.41
2 5.5
0.0141
500
378 33 1/1.41
75.6
5
16 1 1 5.5
0.0200
473
473 0.8
NA
NA 6
64 2 4 5.5
0.0100
515
450 1.6
1/2
87.4 6
128 1.41
2 5.5
0.0700
555
445 27 1/1.41
80.2
6
16 1 1 5.5
0.0800
550
550 0.5
NA
NA 7
64 2 4 5.5
0.0400
600
535 1.0
1/2
89.2 7
128 1.41
2 5.5
0.00283
760
800 3.0
1/1.41
-5.3
7
__________________________________________________________________________
TABLE
5
______________________________________
Plate K.sub.A
2
4
8 Sample #
Pressure reduction factors
Voltage
series
______________________________________
0.51
NA
NA 1
0.54
0.52 0.28 2
0.485
0.70 0.34 3
0.4
0.45 0.18 4
0.65
0.29 0.19 5
0.63
0.43 0.27 6
Mean
0.52
0.44 0.24
.+-.SEM
.+-.0.04 .+-.0.06 .+-.0.03
______________________________________
Plate K.sub.A
2
4
8 Sample #
Voltage reduction as % of maximum
Pressure
Series
______________________________________
99.1
86.9 86.2 1
90.2
87.1 78.6 2
95.2
79.5 75.7 3
87.7
86.5 75.9 4
86.4
87.7 75.6 5
91.7
87.4 80.2 6
Mean
91.7
85.85 78.7
.+-.SEM
.+-.2.1 .+-.1.6 .+-.1.8
______________________________________
EXAMPLE 5
The Effect of Plate Area on the PAGD
Characteristics of Discharge Tubes Enclosing a High Vacuum
The second method used to test the effect of
increasing the electrode plate area in the design of a
discharge tube 50 made use of glass housings 52 enclosing a
final vacuum of 2*10.sup.-6 Torr obtained with a diffusion
pump on. These tests were performed with high direct
currents (200 mA to 1 A). All discharge tubes tested (device
#'s 7 to 13) had an interelectrode gap distance of 5 cm,
enclosed the same volume and the same vacuum, and were
assembled with H34 aluminum plates having plate areas which
varied by an area factor of k.sub.A =2, namely: 16, 32 (not
tested), 64, 128 and 256 cm.sup.2. At a seal off vacuum of
2* 10.sup.-6 Torr, the first two discharge tubes 50 tested
in this series (16 and 64 cm.sup.2, device #'s 7 to 10)
remained unresponsive (no signs of discharge). Even when 3.3
kV was applied, one of the 64 cm.sup.2 discharge tubes
showed only a faint glow (also see discussion of results for
groups #1 and #4 of Table 6 below). The results for the
k.sub.A =2 series are shown in FIG. 16. The results indicate
that when the current, the interelectrode distance and the
pressure are all kept constant, the breakdown potential (Vb)
for the PAGD decreases with an increase in plate area. For
the largest plate area tested (256 cm.sup.2), the PAGD
breakdown (287 V) and extinction (Vx=284 V) voltages
practically coincide, suggesting that larger areas might
depress both Vb and Vx still further. These results were
recorded under identical conditions of applied direct
current (200 mA, closed circles, FIG. 17), of peak pulse RMS
current (open circles, FIG. 17) and of pulse frequency (20
pps), using an earth-grounded centertap power supply with
both positive and negative voltages applied simultaneously
to the respective plates. Under the same conditions of
applied total power (same starting voltage, but higher
applied direct current because of their lower
sustaining/extinction voltage), three discharge tubes 50
built with Alzak plates having areas of 64, 78 and 128
cm.sup.2 respectively were tested with the same power
supply. As shown in FIG. 17, these discharge tubes conduct
5-fold higher DC currents (closed squares, FIG. 17),
transduce 3-fold higher peak pulse RMS currents (open
squares, FIG. 17) and yield a 20 to 30-fold increase in pps
(from 20 to 600 pps) at similar field strengths, when
compared with the results obtained using hardened aluminum
plates.
Table 6 shows the experimental and predicted
results obtained with 4 discharge tubes 50 (device #'s 9,
11, 13 and 17) assembled with hardened aluminum plates, as a
function of scaling the plate area (column D) by a k.sub.A
=2 area factor (column E), while varying the interelectrode
distance inversely with respect to the pressure (group #'s
1-3) or, alternatively, keeping these factors constant
(group #'s 4-6), so that in both instances the pd product is
constant. A plate area k.sub.A factor of 2 corresponds to a
plate linear scaling factor k.sub.L of 2.sup.1/2 =1.41.
Columns A to C show the scaling of the selected linear
dimensions, while column G shows the vacuum measured when
the respective housings 52 were sealed. The space charge
theory of glow discharge holds that the function V, or the
voltage difference at corresponding points, is the same in
k.sub.L -scaled vacuum tubes, the linear dimensions
(including the interelectrode gap distance) of a vacuum tube
"b" being k.sub.L times the linear dimensions of a vacuum
tube "a". Under these conditions where the gap distance also
increases by the k.sub.L factor, the Poisson term d.sup.2 *V
(where d.sup.2 V=r/e.sub.o ; r=density of the attracting
matter at the point chosen (charge density) and e.sub.o
=permittivity of free space) in the interelectrode space of
vacuum tube "a" is k.sub.L.sup.2 times that in vacuum tube
"b", as long as the pressure p changes by 1/k.sub.L so that,
to a first approximation, the breakdown voltage remains the
same. As the permittivity of free space is deemed to be a
constant, the charge density r in vacuum tube "a" is
k.sub.L.sup.2 times that of vacuum tube "b" (the upscaled
device). Consequently, the cathode current density J of
vacuum tube "a" is also expected to be k.sub.L.sup.2 times
that of vacuum tube "b". We can thus summarize these
predictions as: given a linear factor k.sub.L between "a"
and "b", two vacuum tubes will have the same breakdown
voltage if the pressure of "b" decreases by 1/k.sub.L, with
the result that J should decrease by 1/k.sub.L.sup.2 and the
field strength should also decrease by 1/k.sub.L, while
J/p.sup.2 and E/p (where E=electrical field strength) both
remain constant. Essentially, as the area factor between the
two discharge tubes is k.sub.A =k.sub.L.sup.2, both the
charge density r and the current density J should change by
1/k.sub.L.sup.2 =1/k.sub.A, ie inversely to the plate area
factor k.sub.A. The field strengths predicated from the
Poisson term (E=-dV), are shown in column H, and their
corresponding E/p ratios to be expected are shown in column
J. Pulse rate (column L) was kept low and constant, for
purposes of comparison between the groups. The experimental
values measured at breakdown for each device are shown in
Table 6, columns I (for the field strength E) and K (for
E/p). These results indicate that, for k.sub.L (=1.4)-scaled
discharge tubes shown in group #'s 1 to 3, Table 6, having a
k.sub.A =2 and inversely varying p and d values (the product
pd is constant but the pressure and distance terms obey the
k.sub.L -scaling inverse relation) the variation of E is
nonlinear (in fact, one would expect group #2 to be just as
unreactive as group #1, Table 6, at these pressures). The
Table 6 results for k.sub.L (=1.4)-scaled discharge tubes
(group #'s 4-6, corresponding to device #'s 9-10, 11-12 and
13, respectively) with a k.sub.A =2 but separate constant
values for p and d, also show that the field strength E
necessary for breakdown at these high applied currents does
not remain constant and linear, as predicted, but decreases
nonlinearly with an increased plate area, which is the only
factor that changed in the series of group #'s 4-6 (device
#'s 9-10, 11-12 and 13). It is significant that in this
context, the field strength necessary to achieve the same
pulse rate fell by 1/3rd (a factor of 2.8.times.) as the
area increased by a factor of 2, in device #'s 11 and 12
versus 13 (group #'s 5 and 6). This strongly indicates that,
in discharge tubes enclosing a high vacuum obtained under
oil diffusion conditions and stimulated with high currents,
the plate area has a synergistic effect on PAGD production.
The same frequencies of discrete, intense emission were
obtained with lower field strengths for the plasma
discharges triggered by these auto-electronic emissions.
Consequently, in discharge tubes 50, large plate areas
promote PAGD behavior at high vacua and at low field values
not predicted by the space charge theory.
TABLE
6
______________________________________
A
B C
D
F G
W
L Plate
Area
E d p
No. (cm)
(cm) (K.sub.L)
(cm.sup.2)
K.sub.A
(cm)
(Torr)
______________________________________
1
16
4
1 64 1
3.6 2.8 * 10.sup.6
2
32
4 1.41
128 2 5 2.0
* 10.sup.6
3
32
8 1.41
256 2 7 1.4
* 10.sup.6
4
16
4
1 64 1
5 2 * 10.sup.6
5
32
4 1.41
128 2
5 2 * 10.sup.6
6
32
8 1.41
256 2
5 2 * 10.sup.6
______________________________________
H
I
J K
E
E
F/p
E/p L
No. Predicted
Exptl
Predicted
Exptl
PPS
______________________________________
1
21,500 >97,222 7.75 * 10.sup.9
>4.9
* 10.sup.10
0
2
NA
15,480 NA 7.75 *
10.sup.9
20
3
10,320
ND 7.75 * 10.sup.9
ND
ND
4
15,480 >70,000 7.75 * 10.sup.9
>3.5
* 10.sup.10
0
5
NA
15,480 NA 7.75 *
10.sup.9
20
6
15,480 5,600 7.75 *
10.sup.9
2.8
* 10.sup.9
20
______________________________________
NA = Not Applicable
ND = Not Determined
A comparison of pulse counts at the axial
probe 62 (see FIGS. 2 and 4) in discharge tubes 50 and the
pulse counts at the cathode 54 showed that the axial probe
62 accurately reflects interelectrode events. This
correspondence was confirmed using oscillographic analysis
of the probe waveform, which showed it to be functionally
equivalent to that measured at the cathode 54. FIG. 18 shows
voltage and current oscillographs over time of AGD
self-generated auto-electronic emission pulses (at 10 pps)
in an H34 128 cm.sup.2 discharge tube 50 (device #1),
registered as amplitude discontinuities between the anode
56/cathode 54 in FIG. 18A, as current pulses at the cathode
54 in FIG. 18B and as dual polarity field direction
reversals of a split axial probe 62 in FIG. 18C. Typically,
for a closed high vacuum discharge tube 50 with a plate area
of 128 cm.sup.2 and an interelectrode gap of 5 cm, a
breakdown potential of 668 volts, an average applied current
of 500 ma, and at 200 pps, the pulse amplitude is more than
300 volts. Under rotary pumpdown conditions and for an
identical discharge tube, the pulse amplitude (encompassing
both positive and negative components, the latter being the
prominent value) increases with decreasing pressure, from 60
volts at about 0.5 Torr (with 5 mA DC) to greater than 300
volts at 0.008 Torr. In the closed high vacuum discharge
tube with H34 plates having an area of 128 cm.sup.2 (device
#1), higher resolution oscillographs taken at the axial
probe 62, show that the negative component precedes the
positive reversal and has a typically higher amplitude (140
V vs. 80 to 120 V, respectively, for this situation shown in
FIG. 18C). Clearly, upon an abnormal glow discharge pulse,
the recovery of the field strength within these discharge
tubes overshoots a `closed switch state` (where the current
I approaches zero) and results in a net flow of positive
charge past the probe, towards the cathode (which is the
floating ground reference level for these measurements).
EXAMPLE 6
Using the same breakdown voltage of about 668
VDC, the effect of varying the capacitance of the power
supply, set in parallel with the discharge tube (device #1),
on the frequency of PAGD production was determined while
maintaining all other variables constant (interelectrode
gap, plate area, applied voltage and current levels). The
linear regression in FIG. 19 shows that, under these
conditions, the PAGD frequency is increased by lower
capacitances. The log slope indicates that the pps rate is
doubled as the capacitance decreases by 2/3rds. Measurements
were also taken of the `non-dynamic` capacitances of
discharge tubes with H34 aluminum plates having different
plate areas. These were insignificant when compared with the
parallel capacitances used in the power supply in tests
illustrated in FIG. 16, and were observed to vary in
accordance with the dielectric law, ie. doubling the plate
doubled the capacitance. Thus for a plate area of 64 square
cm, capacitance of 1 pF, for 128 sq. cm, 2.05 pF, and for
256 sq. cm, 4.1 pF.
Further Factors Influencing PAGD Production
Prolonged operation of discharge tubes 50 has
provided some geometrical guidelines for promoting PAGD
production:
1) it is advantageous if the discharge does
not wander to the back of the cathode 54 and this is
facilitated by using a semi-cylindrical cathode in
cylindrical housings 52 and a flat cathode (rectangular,
square or circular) in parallelepiped-shaped housings 64
(see FIGS. 3 & 5). However, interelectrode gap tests are
best done with flat plates which assure a homogenous
potential. Moreover, the semicylindrical electrodes are best
made of hardened aluminum, at least 0.5 to 1 mm thick, and
this requires forming them to the right curvature, given
that foil alternatives are not resistant to the deleterious
effect of high-current PAGD transduction at very high
frequencies and do not withstand distruptive VAD discharges.
Nonetheless, a semi-cylindrical electrode configuration in a
housing 52 makes the sheaths (where ionic recombination
occurs during glow discharge) near the electrodes and the
housing wall coincide, and this can be highly advantageous
for sustaining PAGD production. The same applies to flat
plates in flat surface parallelepiped housings 64.
2) The most effective axial probe 62 is either
a single half-length rigid rod or a pair of axial probes 62
separated at the center of the discharge tube 50 by a gap of
more than 1 cm, 4-6 cm being optimum. Whereas an axial wire
will perform satisfactorily as a probe 62, the rigid rod has
the advantage of not yielding to a direct mechanical
transduction of the electrodynamic force effected upon it by
the discharge or to force created by the acquisition of a
constant space charge. A split axial probe 62 facilitates
the exciter function and assures PAGD operation by
preventing a formation of a stable axial space-charge at
high-current operation.
3) A cooling coil (made of rubber, polymer,
glass or copper tubing) surrounding housing 52/64 is useful
to counterbalance the heating of the anode 56/cathode 54
which promotes the production of semi-thermionic VAD
channels and even thermionic normal glow discharges. A
coolant pipe system that weaves through the plates can also
be used for this purpose, in which case flat plates are
preferred.
4) Larger anode 56/cathode 54 surfaces are
required as the interelectrode gap is increased. And
inversely, larger anode 54/cathode 56 surfaces operate best
if larger interelectrode gaps are used; however, the
breakdown voltage also increases with larger interelectrode
gaps.
5) One of the limitations of these discharge
tubes stems from their continuous operation at high applied
currents and from eventual slippage into the VAD regime,
both of which promote a deposit of sputtered metal atoms on
the inner walls of the housing 52, 64 thereby making them
conductive. In order to minimize this problem,
electromagnets may be wound longitudinally over the housing
52, 64 (one at each end), to limit lateral dispersion of the
discharge vortices.
It is apparent that several factors affect
PAGD production namely: cold cathode work function, voltage,
current, parallel capacitance, gas fill, pressure, geometry
plate area and interelectrode gap distance. Except for
capacitance at the high end of the scale, each of these
factors affect the high and low limits of the PAGD, for any
given set of conditions. Heretofore, parameters such as
plate area in vacuum tubes have not been previously
identified as factors which affect the breakdown field
values and the sustaining/extinction potentials of a glow or
an arc discharge. This suggests that the observed
auto-electronic field emission in the PAGD regime is a
function of physical factors which to date have been
unrecognized. It further suggests that field emission is not
a property exclusive to the VAD, ie. that it is also a
property of the pulsed operation of an abnormal glow
discharge in low to very high vacua.
The present discharge tubes 50 provide a
design capable of transducing high peak pulse currents at
very low field strength, over a wide range of frequencies
with minimal slippage of the PAGD operation into either the
NGD or the VAD regimes.
Although the examples described above utilise
discharge tubes with symmetrical anode and cathode plates
and floating probe electrodes, many other arrangements are
possible. Thus the characteristics of the tubes may be
adjusted by connecting the probe (or probes) through a
capacitor to the anode or cathode to form an auxiliary anode
or cathode.
Since only the cathode need be have an
extended surface area, the probe of the tubes described may
be connected as an anode, with the plate electrodes
connected as either strapped or independent cathodes.
Examples of such connections are shown in FIGS. 21A and 21B,
which show how to incorporate a discharge tube operating in
the PAGD regime in an inverter circuit so that the pulse
output may be utilized by a remotely located alternating
current device. The intermittency of the pulses produced by
the arrangements described above are not conducive to
efficient operation of conventional transformers, and a
push-pull circuit arrangement is preferred. While such an
arrangement could utilize two discharge tubes, an
advantageous arrangement utilizes a single tube of the type
described in the parent application, as shown in FIG. 21A.
In this instance, both plates 8a and 8b of the tube act as
cathodes and are connected to the diode 5, and the probe or
auxiliary electrode, which is typically of tungsten, acts as
a common anode 9 and is connected to the diode 6. The
capacitors 10a and 10b are connected to opposite ends of a
centre-tapped primary winding of a transformer 26, providing
an alternating circuit output through a secondary winding.
The centre-tap of the primary winding is connected to the
electrode 9. The two halves of the primary winding
inductively couple the cathode circuits in antiphase, thus
synchronising the PAGD pulse trains involving the two
cathodes in antiphase.
In a modification of the circuit, shown in
FIG. 21B, the capacitors 10a and 10b are connected directly
to the electrode 9, and the primary of the transformer 26 is
connected directly between the two cathodes with its centre
tap connected to the diode 5. Whilst this arrangement bears
some superficial resemblance to known inverter circuits
employing VAD devices, it should be noted that the circuit
is completely self-commutating, and does not need moving
external magnetic fields to provide commutation as in the
prior art.
The electrodes themselves may be formed in
various configurations. Provided that both the anode and
cathode electrodes have sufficiently low impedance to
sustain the current densities associated with PAGD without
rapid deterioration or overheating, particularly of the
cathode, and provided that the cathode presents a surface of
extended area to the anode and is sufficiently separated
from it that the cathodic plasma eruptions associated with
AGD do not reach the anode to complete a VAD channel, the
electrode separation and cathode surface area can be varied
over a wide range. Large cathode surface areas tend to
reduce the potential required to initiate AGD, and reduced
electrode separations increase the risk of entering the VAD
region. In practice the cathode area should usually be at
least 2 sq. cm and preferably at least 16 sq. cm, and the
electrode spacing should be at least 2 cm and preferably at
least 3.5 cm.
Particularly when the probe is used as an
anode, it may advantageously be formed as a wire grid or
mesh parallel to one or more plate electrodes acting as a
cathode or cathodes. Cathodes may be arranged on one or both
sides, or surounding a rod anode, or facing a point anode.
Table 7 shows PAGD frequency results for
various electrode configurations which have been tested.
Configuration sd is a diode with plate electrodes and no
probe, and configuration sd* adds an unconnected axial
probe. In configuration t the probe was connected by a
capacitor to the cathode. Configurations dd1 and dd2 use
double diode configurations, with plate cathodes and an
intermediate anode, a rod in the first case and a plate in
the second case. Configuration cd used a cylindrical cathode
and an axial rod anode. These tests indicate that an
extended area of both the anode and cathode is desirable,
although the area of the cathode has a greater influence.
TABLE
7
______________________________________
"Broken in" H34 cathodes (128 cm.sup.2
plates for all configurations
except cd; >1 .times. 10.sup.6 pulses)
at 0.8 Torr pressure, 6 cm
distance
between plates, 3 cm distance of plate to
axial or intercalated
member, when applicable. V.about.540DC;
Iav = 0.3A.
PPS
(@
1' running
Gap
Configuration where n = 30)
in
cm.
______________________________________
sd
10
.+-. 2 6 cm.
sd*
6
.+-. 3 6 cm.
t
19
.+-. 4 6 cm.
dd
(1) 65
.+-. 11 3 cm.
dd
(2) 88 .+-.
7 3 cm.
cd.sup.o 121 .+-. 14 3
cm.
______________________________________
sd* = single plate diode with axial
member not conected
cd.sup.o = cylindrical cathode area
of 876.5 cm.sup.2
The anode is preferably formed of metal of a
relatively high work function, and the cathode of metal of a
comparatively low work function, although in many cases the
same material may be used for both as exemplified above. In
discharge tubes, where it is desired to be able to reverse
plate polarity, utilisation of the same metal for both
electrodes will be advantageous. For axial probes or axial
anodes, tungsten will give good results. Hollow or solid
rods of the same metals selected for the cathodes may also
be employed. Axial rods of tungsten or other selected metals
may also be used as cathodes provided that they present
sufficient surface area to th anode.
The best cathode materials identified to date
are aluminum and its alloys, zinc, nickel, soft iron and
silver. Cathodes made of copper and its alloys, and of
steel, support PAGD but are of much poorer performance.
In Table 8 sampled data from experiments
performed with different cathode metals (elemental or
alloys) are shown. Except for the first two entries in Table
8, which utilized a perpendicular "surface-to-point" type
configuration (with the "point" being the lateral area of a
tungsten rod utilized as a cathode), all the other entries
were obtained with single diode configurations, utilizing
parallel plates at various gap distances. Most of the column
headings are self-explanatory, but it should be noted that
the voltages shown are breakdown values which, when
indicated, are also minimal breakdown voltages for the
discharge type shown.
As exemplified in entries 1 and 2, for two
different Argon pressures, tungsten cathodes can support the
same cold-cathode type of low-field spontaneous emission
responsible for the PAGD regime which we have identified in
diverse aluminum cathodes. This matches the previous
observation of such discontinuous emissions being aided by
an axial tungsten member when discharge tubes with aluminum
plates are connected in the triode configuration. A higher
potential (750 VDC), however, is needed with this
configuration and tungsten cathodes, than that required by
the lowest area aluminum plates tested (cp entries 1 and 2
with 3-7).
In entries 3 to 12, small (4 cm2) H34 aluminum
plates are compared for different gap distances (3 vs. 9
cm), and within each group (entries 3 to 7, and entries 8 to
12) for varying pressure and nature of the residual gas. The
net effect of increasing the gap distance is to increase the
potential needed for electrical breakdown of the vacuum (cp
VDC values for entries 4-7 with 9-12), as expected from
Paschen's law. A trend for higher PAGD input currents, as a
function of the higher vacua, is also apparent throughout
this group.
In entries 13 to 28, wider aluminum cathodes
(16 cm2) were compared at two different gap distances (2 and
4 cm, respectively, for entries 13 to 20 and 21 to 28), for
different pressures in air or argon atmospheres. At the same
specified battery breakdown voltages utilized, the shorter
gap produces much higher PAGD frequencies (100 PPS vs 30-52
at 0.8 T Argon, respectively, entry 14 and entries 25 and
28). The shorter gap also promotes the setting in of a
vacuum arc discharge, when compared to the larger gap at the
same voltage and potential (cp entry 16 with entry 26).
Lastly, it is apparent that the PAGD frequency equally
increases in the presence of argon (entries 24-26) with
respect to air (entries 21-23), and with increasing input
current (see entries 17 to 19) within the current range
characteristic of the PAGD at the same pressure (1 Torr).
In entries 29 to 35, and 75 to 76, utilization
of brass cathodes is examined for purposes of PAGD
production. Within the PAGD current and voltage ranges
determined for aluminum and other metals, brass cathodes
perform poorly, with low or very low pulsation frequencies
(entries 30, 31 and 76) and very erratic bursts of activity
(entries 32, 34 and 35). Unlike the typically single
aluminum and tungsten PAGD emission foci, brass presents
multiple small cathode spot localizations in the same pulse.
The pulsed emission, however, like those of aluminum,
follows the same cyclic path of abnormal glow saturation,
focusing of the discharge at the emission foci, and
subsequent collapse of the saturated glow.
Results for bronze-aluminum alloy cathodes are
shown in entries 36 to 41, and they indicate that this alloy
does not perform as satisfactorily as aluminum for PAGD
production, but it is certainly utilizable. However, like
brass, in the presence of Argon, erratic bursts of emission
pulses are also observed (cf entry 41), without the
development of a VAD-type regime.
Iron, nickel and zinc cathodes, tested in the
following sequences (respectively entries 42-50, 51-53, and
54-60), proved to be amongst the best cathodes for PAGD
production this purpose. Quasi-regular high PAGD frequencies
are possible utilizing these metals (cp entry 49 & entry
60), which appeared to perform best with argon rather than
air. Iron plates seem to eject the least metal and can
sustain very regular frequencies of pulsed abnormal glow
discharges. Zinc cathodes ejected the most metal and most
easily slipped into a vacuum arc discharge having the aspect
of a meandering flame surrounding the cathodes spots. With
zinc cathodes, the VAD regime would onset in air at pressure
and current values characteristic of the PAGD regime in
Argon (cp entry 55 with entry 60), the window of the
transition between the NGD and the VAD being rather narrow
or absent. Even in Argon, this window remained relatively
narrow in terms of its pressure range.
Tubes for pulse generators were also built
with apposed cylindrical section electrodes made of silver
nitrate directly coated onto the glass inner surface, and
having a cross- section fundamentally identical to that of
FIG. 4. Because of this geometry, the gap distance given is
the average distance between the center and the extremities
of the cylindrical electrodes. Experiments with such a
device showed that silver in greater thickness would also
form a suitable cathode to support PAGD production (entries
64 and 65). The emission loci in silver form single cathode
spots for each pulse generated, as with aluminum, tungsten,
zinc, nickel and iron cathodes; however, these intermittent
silver cathode emitters travel laterally to form
quasi-continuous tracks of ejected cathode material.
Lastly, 64 cm2 wide copper and aluminum plates
were compared, in entries 66-74 and 61-63, respectively. In
the presence of air, under the same pressure, applied
voltage and current conditions, copper cathodes do not
support PAGD production (unless triggered by external
proximity of high-frequency spark gaps, eg a Tesla coil, or
a moving static charge, or a moving magnetic field), whereas
aluminum cathodes do (cp entries 61 and 66). However, in
argon (entries 68, 70-72) or helium (entries 73-74)
atmospheres, copper cathodes readily supported PAGD
production, though they required greater input currents to
attain about half the PAGD frequency observed using aluminum
plates. The PAGD region is also particularly narrow with the
copper cathodes, when the voltage and current are at
threshold levels needed for eliciting the regime (cf entries
68 and 69). It is easy to see the slowing down of the PAGD
frequency in these cathodes, apparently due to the rapid
heating of their surface (also observed with brass and
bronze alloys): the cycle of onset of an abnormal cathode
glow, followed by a localized cathode eruption, then by a
total or partial collapse of the abnormal glow onto the
electrodes and its subsequent re- instatement, slows down
progressively as the setting in of the cathode glow becomes
more intense in luminosity and finally ceases giving way to
the auto-electronic emission. A semi-thermionic abnormal
glow discharge then sets in. This transition of the PAGD
regime to a semi-thermionic AGD regime, in tubes using
copper cathodes, is all the more prevalent as higher
frequencies and higher currents are employed to stimulate
the pulse generator, and it may explain the observed erratic
behaviour of the copper-containing alloys, brass and bronze.
Finally, the copper cathode emissions accompanying a single
pulse were not single but multiple, and clustered in a
neighbourhood, as was also observed in brass and
bronze-aluminum alloys.
All the above PAGD cathode emitters that had
reasonable characteristics (regular or quasi-regular
spontaneous pulse discharges) presented a bell-like
distribution for the discharge frequency, with the higher
vacua beyond a given pressure having the effect of
decreasing the frequency of the PAGD emission, while
increasing the input and output peak currents as well as the
cathode voltage drop of each pulse. Lastly, caesium emitters
were also employed at these input currents to support PAGD
production successfully. Other metals considered promising
are bismuth, cadmium and antimony.
TABLE
8
__________________________________________________________________________
Cathode Area Pressure
Discharge
gap
Material cm2
Gas
in Torr
PPS
type in cm
VDC
DCA
__________________________________________________________________________
1 Tungsten
0.5
Argon
0.8
4 PAGD 4 750 0.2
min.
2 Tungsten
0.5
Argon
0.5
18 PAGD 4 750 0.3
3 Aluminum
4
Air 0.9 1 PAGD 3 564 0.2
(H34)
4 Aluminum
4
Argon
0.9
2 PAGD 3 564 0.3
(H34)
5 Aluminum
4
Argon
0.7
1.5 PAGD 3 564 0.4
(H34)
6 Aluminum
4
Argon
0.4
12 PAGD 3 564 0.45
(H34)
7 Aluminum
4
Argon
0.3
0.5 PAGD 3 564 0.5
(H34)
8 Aluminum
4
Argon
4-0.01
0
None# 9 564 0
(H34)
9 Aluminum
4
Argon
0.9
3.5 PAGD 9 850 0.4
(H34)
min.
10 Aluminum
4
Argon
0.4
20 PAGD 9 900 0.45
(R34)
min.
11 Aluminum
4
Argon
0.2
2 PAGD 9 950 0.5
(R34)
min.
12 Aluminum
4
Argon
0.1
I PAGD 9 950 0.5
(H34)
min.
13 Aluminum
16
Argon
2.0
50 PAGD 2 560 0.8
(H34)
14 Aluminum
16
Argon
0.8
100 PAGD 2 560 1.2
(H34)
15 Aluminum
16
Argon
0.3
10 PAGD 2 560 0.4
(H34)
16 Aluminum
16
Argon
0.3
erratic
VAD#
2 560 1.1
(H34)
17 Aluminum
16
Argon
1.0
20 PAGD 2 260 0.05
(H34)
min.
18 Aluminum
16
Argon
1.0
100 PAGD 2 260 0.7
(H34)
min.
19 Aluminum
16
Argon
1.0
185 PAGD 2 260 1.6
(H34)
min.
20 Aluminum
16
Argon
0.1
2.5 PAGD 2 350 0.03
(H34)
21 Aluminum
16
Air 0.8 0.4 PAGD 4 560 0.3
(H34)
22 Aluminum
16
Air 0.5 20 PAGD 4 560 0.5
(H34)
23 Aluminum
16
Air 0.3 1.2 PAGD 4 560 0.5
(H34)
24 Aluminum
16
Argon
1.0
1.2 PAGD 4 560 0.5
(H34)
25 Aluminum
16
Argon
0.8
30 PAGD 4 560 0.6
(H34)
26 Aluminum
16
Argon
0.3
8 PAGD 4 560 0.7
(H34)
27 Aluminum
16
Argon
0.8
10 PAGD 4 550 0.2
(H34)
28 Aluminum
16
Argon
0.8
52 PAGD 4 550 1.0
(H34)
29 Brass 16 Air 2-0.6
0
None 4 560 0
30 Brass 16 Air 0.01 0.01
PAGD
4 560 ND
31 Brass 16 Air 0.3 0.4 PAGD
4 560 0.3
32 Brass 16 Air 0.2 bursts
PAGD#
4 720 ND
33 Brass 16 Argon
2-0.3
0
None* 4 560 0
34 Brass 16 Argon
0.9
bursts
PAGD#
4 630 0.5
min.
35 Brass 16 Argon
0.8
.about.20
PAGD
4 750 0.7
erratic
36 Bronze-
16
Argon
1
0 None 4 568 0
Aluminum
37 Bronze-
16
Argon
0.5
0.4 PAGD 4 568 0.3
Aluminum
38 Bronze-
16
Argon
0.3
0.6 PAGD 4 568 0.3
Aluminum
39 Bronze-
16
Argon
0.8
1 PAGD# 4 570 0.35
Aluminum
40 Bronze-
16
Argon
0.8
2.8 PAGD 4 750 0.4
Aluminum
41 Bronze-
16
Air 0.3 5-15
PAGD#
4 750 0.5
Aluminum
42 Iron 16 Air 0.3/0.8
0
PAGD 4 560 0
43 Iron 16 Air 0.25/0.18
0.2
PAGD 4 560 0.3
44 Iron 16 Argon
0.8
0.12
PAGD
4 560 0.3
45 Iron 16 Argon
0.6
0.4 PAGD 4 560 ND
46 Iron 16 Argon
0.4
0 PAGD 4 560 0
47 Iron 16 Argon
2.0
3 PAGD 4 720 0.4
48 Iron 16 Argon
1.0
1 PAGD 4 750 0.3
49 Iron 16 Argon
1.0
26 PAGD 4 950 1.05
50 Iron 16 Argon
0.8
0.1 PAGD 4 720 0.8
51 Nickel
16
Argon
2
1 PAGD 9 1000 0.2
52 Nickel
16
Argon
1
2 PAGD 9 950 0.3
53 Nickel
16
Argon
0.5
0.5 PAGD 9 1000 0.2
54 Zinc 16 Air 2-0.8
0
VAD 4 564 1.6-1.3
55 Zinc 16 Air 2-0.8
0
VAD 4 564 0.8
56 Zinc 16 Air 0.8-0.2
0
th. AGD
4
564 0.03
57 Zinc 16 Argon
2-0.8
0
VAD 4 564 1.8-1.2
58 Zinc 16 Argon
0.9-0.2
0
th.AGD
4
560
0.1/1000
59 Zinc 16 Argon
1.0
1 PAGD 4 560 0.3
60 Zinc 16 Argon
1.0
23 PAGD 4 950 1.0
d1 Aluminum
64
Air 0.8 5 PAGD 5.5 560 0.4
(H34)
.about.2
Aluminum
64
Argon
0.8
12 PAGD 5.5 560 0.5
(H34)
63 Aluminum
64
Argon
0.8
62 PAGD 5.5 540 0.9
(R34)
64 Silver
64
Argon
0.8
10 PAGD 5.5 560 0.2
65 Silver
64
Argon
0.2
1.2 PAGD 5.5 560 0.7
66 Copper
64
Air 4-0.01
0
None* 5.5 560 mD
67 Copper
64
Argon
4-0.4
0
None* 5.5 560 ND
68 Copper
64
Argon
0.3
0.44
PAGD#
5.5 560 0.5
69 Copper
64
Argon
0.25
0 Th. AGD
5.5
560 0
70 Copper
64
Argon
0.8
5 PAGD 5.5 580 0.2
min.
71 Copper
64
Argon
0.8
33 PAGD 5.5 580 0.9
72 Copper
64
Argon
0.1
1 PAGD 5.5 900 0.5
min.
73 Copper
64
Helium
0.9
0 None *
5.5
560 0
74 Copper
64
Helium
0.2
0.5 PAGD 5.5 560 0.7
min.
75 Brass 64 Argon
4-0.6
0
None *
4
560 0
76 Brass 64 Argon
0.5
0.2 PAGD 4 560 0.3
__________________________________________________________________________
*Single pulses of abnormal glow
discharge could be elicited by moving
static charges or the proximity of
high frequency alternating currents.
# PAGD production was erratic.
Shaping of the cathode is not critical,
although it should be such as to provide a reasonably
uniform distance between different parts of its surface and
the anode. Cylindrical or multiple part cylindrical
electrodes may conveniently be used with rod anodes, or a
flat cathode when the anode is a flat plate or mesh, or the
electrode separation is large. Walls of the discharge tube
should be sufficiently spaced from the electrodes that metal
sputtered from the cathode does not build up a path for
arcing or act as an auxiliary electrode modifying the
characteristics of the tube.
The static and dynamic characteristics of the
external circuit which cooperates with the tube must be such
as to prevent the plasma eruptions from the cathode during
PAGD from acquiring sufficient energy to reach the anode and
forming a continuous VAD channel. This involves inter alia
the physical dimensions of the tube, its gas content, the
impedance of the supply and any associated ballast resistor,
and the energy storage capacity of any reactive components
in the pulse generator circuit, such that the potential
across the tube falls below the AGD extinction potential
before a plasma channel to the anode is established.
Although it may be possible to acieve this with a very small
cathode area or small interelectrode gap, the amounts of
energy involved in creating the plasma eruptions and
released by their collapse will likely become too small to
be useful.
In conclusion, we have developed a series of
pulse generators exploiting the abnormal glow discharge
regime, as well as a series of low to very high vacuum
discharge tubes which support the production of PAGDs. In
testing these devices we have shown that:
the low field strengths and typical low
emission current densities observed in the PAGD regime are
not predicted by any existing field emission or space-charge
theories;
the PAGD regime responds asymmetrically to the
polarity of the applied voltage at high applied currents;
at low applied currents, the PAGD pulse rate
increases with the applied voltage and the current up to an
observed plateau;
at mid to high applied currents, the PAGD
pulse rate increases with an increase in current and with a
lowering of the extinction potential;
the PAGD pulse rate also varies with the
composition of the cathode material (the pulse rate is
promoted by materials having a low work function) and
increases with a decrease in pressure, during pumpdown, to a
maximal peak rate, thereafter either diminishing to the
point at which the discharge extinguishes or gives way to
x-ray production (depending on the magnitude of the applied
potential);
larger area plates lower the field strength
values needed to elicit comparable PAGD production, displace
the PAGD region downward in the pressure scale and increase
the peak PAGD rate;
higher power supply capacitances slow down the
PAGD rate.
Exploitation of PAGD permits the production of
highly efficient pulse generators for the production of
endogenously generated abnormal glow discharge pulses
triggered by intense, cathodic auto-electronic emissions
under conditions of a constantly applied DC potential.
These pulse generators have diverse industrial
applications; directly, they may be used as stroboscopic
light sources, for vacuum deposition of cathode materials or
cathode coatings (eg. polymer deposition or aluminum
mirroring of target surfaces), detection of ionizing
radiation fields, or electrostatic and electromagnetic
proximity fields, high power noise-signal generation,
destructive component testing (transient response) or
destructive testing of materials in vacua (eg. insulations),
high frequency medium voltage power supply applications
(switching supplies and inverters), as an oscillator or as
part of a pulse forming network. Indirectly, they may be
used for laser pulsing, flash tube pulsing or for research
(eg. chemical reaction triggering) and industrial switching
applications.
Average Electrode Current Densities
Table 9 shows additional data related to that
of Example 5 and Table 6. In Table 9, columns A through G
are the same as in Table 6 for ease of reference. Current
densities (Table 9, columns I and M) for the overall
electrode areas employed were determined experimentally and
compared to the values predicted on the basis of the glow
discharge theory (Table 9, columns H and L), under the same
conditions and with the same devices as described in Example
5. As explained above in Example 5, and given a linear
factor k.sub.L, two vacuum tubes "a" and "b", will have the
same breakdown voltage if the pressure of "b" decreases by
1/k.sub.L, with the result that J (the average electrode
current density) should decrease by 1/k.sub.L 2 while
J/p.sup.2 should remain constant (if the pressure varies).
Predicted and experimentally determined J/p.sup.2 values are
shown in columns J and K of Table 9. Essentially, as the
area factor between the two pulse generators is k.sub.A
=k.sub.L 2, both the charge density r and the current
density J should change by 1/k.sub.L 2=1/k.sub.A, ie.
inversely to the plate area factor k.sub.A. This is indeed
what is observed at breakdown (Vb), for invariant pressure
groups 5 and 6, columns H to K, Table 9. The same relation
however does not apply as a function of the maximum input
power and lowest sustaining or extinction voltages (columns
L to O, Table 1), respectively, 676 and 368 V, as the plate
current density and J/p.sup.2 values of the same groups 5
and 6 are virtually identical, despite the invariant
pressure and the k.sub.A =k.sub.L 2 area factor between the
two pulse generators.
Examples of typical average electrode current
densities encountered in the PAGD regime are shown in Table
10 for different area aluminum plates, as a function of the
input current. Electrode J values vary from 10.sup.-2
A/m.sup.2 to 10.sup.3 A/m.sup.2.
Emission Structure, Area and Current Densities
Determination of the videographed equatorial
diameter of the inner core of the cathode plasma ball at the
base of each PAGD channel allowed us to approximate grossly
the emission area per pulse and the pulse current density at
the emitter surface, utilizing a reactor (#1 of Table 1)
built with H34 aluminum plates. Measurements were taken
laterally from the extreme infra-red light component alone
of the pulsed abnormal discharges at fully closed aperture.
At PAGD breakdown voltages (Vb) of 1100 to
1350, the mean equatorial area of the cathode plasma globule
was 2.8.+-.0.03 mm.sup.2. At PAGD plateau breakdown (Vb)
voltages of 700 to 850 volts, the mean equatorial area of
the cathode PAGD plasma globules were 3.8 and 0.95 mm.sup.2
with anode and cathode voltages respectively (#4 and 2,
Table 11). As indicated by the input current progression of
groups 2 to 5, the mean equatorial area of the cathode
plasma globule increases with increasing input current (cf
columns B and C, Table 11). Group 6, Table 11 shows similar
results for an Alzak cathode. This Videographic
determination of the mean equatorial area of the cathode
plasma globule allowed an estimation of the overall emission
area, and thus the calculation of (uncorrected) emission
current densities (J.sub.cm), shown in column D, Table 11.
Autographic analysis of the PAGD-induced
cathode craters in Alzak plates was performed next, and
their aspect, average inner diameter and maximal depth were
determined (device 2 of Table 1) after 30 seconds of
operation at 500 PPS, Only isolated craters were measured,
following the autograph method of Daalder (Daalder, J. E.
(1974) "Diameter and current density of single and multiple
cathode discharges in vacuum", IEEE Trans Power Appar Syst,
PAS-93:1747). The PAGD operation, at levels where Vb and Vx
were very close, showed a discharge that, despite the
smoothness of the surface, tended to move over most of the
cathode, with the highest concentration of emission craters
found at the lateral edges. After PAGD operation, two types
and sizes of craters could be observed:
1) the large type, or primary craters, which
had an average inner diameter of 0.28.+-.0.03 mm and a mean
area of 0.000615.+-.SE 7*10.sup.-5 cm.sup.2, see group 9,
Table 11;
2) smaller pits, typically distributed
radially around a major crater or a cluster of these, and
which have a mean diameter of 5.5 .mu.m.
The primary craters often occur in discrete
clusters of 2 to >10 such craters, defining surface
neighbourhood regions of PAGD emission where the discharge
repetitively struck. The inner or bottom circular area of
the primary craters characteristically shows a twirl or
swirling pattern of molten metal along one of its diameters
with solidified metal droplets scattered about. Gross
macroscopic examination of these craters exhibits a whitish
periphery.
A comparison of the emission area values
obtained by the autographic method of crater size
determination and the videographic method of measuring the
equatorial cathode ball diameter, indicates a substantial
divergence between them, and the resultant estimation of the
current density at the primary emission site. The reason for
the discrepancy between the two methods appears to be due to
the emission structure encountered micrographically: even
though measurements of the luminous emission globules did
not include the zones of less intense luminosity (the
fringe), metallographic examination showed that each focus
of emission had a multiplicity of minor emission craters
associated with it; these secondary craters were dispersed
in a radius of three to four primary crater diameters from
the primary crater's center, and they thereby increased the
total area involved in associated emission to an average of
0.037 cm.sup.2. This corresponds rather well to the obtained
videographic value of an area of 0.044 cm.sup.2 for the
cathode plasma globules in Alzak plates, (group 6 of Table
11) as measured on the cathode that was later disassembled
for autographic analysis. Typically, the videographic method
over estimates the area of primary emission site by 62 to
88.times.. The two methods thus identify distinct structures
of the emission process: whereas the metallographic method
identifies primary emission sites, the videographic method
identifies the overall area of the emission complex which
includes the secondary craters associated with the primary
emission site. Due to these findings, and based upon the
metallographic measurements, a general correction factor of
75.times. was applied to determine the PAGD emission areas
and current densities at the primary emission site measured
videographically, as shown in group #'s 1 to 6, columns F to
H, Table 11. These values correspond well with the values
obtained, for the same type of plate material, by the
metallographic method (compare for example group 6 with
group 9), to the advantage of the videographic method which
does not require disassembly of the reactor. With this
approach, PAGD primary emission site current densities as
low as 1 to 2.5*10.sup.5 have been measured.
Autographic analysis of the PAGD-induced
cathode craters in H34 plates was equally performed, and
their average inner diameter and maximal depth determined,
examples of which are given in groups 7 and 8, Table 11. The
secondary craters characteristically found in Alzak plates,
along fracture lines radiating from the main crater, are
absent in H34 plates; instead, in H34 plates, one observes a
roughened surface surrounding the emission crater, quite
distinct from the original rough aspect of the pulled finish
of these hardened aluminum plates. Also unlike the Alzak
main craters, the H34 craters often have a convex center
occupied by a cooled molten metal droplet, whereas the Alzak
craters had a concave, hollowed out aspect.
With the data obtained by the metallographic
method of crater measurement, we estimated the volume of
metal ejected from the cathode, by assuming that the crater
represents a concavity analogous to a spherical segment
having a single base (1/6.pi.*H 3r.sup.2 +H.sup.2 !, where H
is the height of the spherical segment and r the radius of
the sphere), while disregarding the volume of the central
droplet leftover from the emission. The following are mean
crater diameters (D), crater depths (H) and volumes (V) of
ejected metallic material for two types of aluminum
cathodes, Alzak and H34 hardened aluminum, subject to a high
input current PAGD:
1--Alzak:D-0.028 cm.+-.0.003; H-0.002
cm.+-.0.0002; V-6.2*10.sup.-7 cm.sup.3 ;
2--H34:D-0.0115 cm.+-.0.0004;
H-0.0006.+-.0.0001; V-3.1*10.sup.-8 cm.sup.3 ;
These data indicate that, on the basis of the
input currents, the PAGD reactors do not reach the critical
value of about 7*10.sup.8 A/m.sup.2 ie the threshold
required by the Fowler-Nordheim theory for field emission.
Nonetheless, auto-electronic emission is occurring, at low
applied fields and low emission current densities. Based on
measurements of the peak pulse current developed by the
reactor, there is an anomalous reaction current set up
within the reactor. This is exemplified in FIG. 18B. These
anomalous reaction currents may be as low as 100 mA but,
under conditions of most interest, are of the order of 0.5
to >200 A. On the basis of this anomalous reaction
current phenomenon, primary emission current densities of
the order of 10.sup.7 to 10.sup.9 A/m.sup.2 can be
calculated.
Low Field Emission
Unlike prior art planar or coaxial electrode
discharge devices (eg Boetcher, U.S. Pat. No. 3,663,855;
Conrad, U.S. Pat. No. 4,764,394; Alexandrovich, et al, U.S.
Pat. No. 3,821,580; Dethlefsen, U.S. Pat. No. 5,126,638),
which utilize short gap and high field primary or trigger
discharges (typically >100,000 V/m), the PAGD reactors
are essentially low breakdown field devices with long gaps,
and which advantageously employ the area effect to reduce
the field strength, as described previously with reference
to FIG. 11. Typical examples of the values of the PAGD
breakdown fields at various negative pressures, for aluminum
and nickel cathodes of reactors that were sealed (at
diffusion pump vacua) or pumped down (by rotary pump
action), are shown in Table 12. The breakdown field values
mostly range from 5,000 to about 30,000 V/m. Similar ranges
are shown in FIG. 11 where PAGD breakdown fields can be seen
to vary from a minimum of 2,730-5,090 V/m to a maximum of
15,640 V/m. (Extinction field values may be as low as 1,000
to 2,000 V/m.) As previously discussed, the breakdown field
value is modulated by the voltage reduction area effect, the
interelectrode gap distance and the residual gas pressure in
the gap. Generally, increasing the gap distance increases
the required field strength. The voltage reduction effect of
large area electrodes appears to be mainly responsible for
the low field breakdown characteristics of the
self-generating auto-electronic emissions encountered in the
PAGD regime. Field-emission theory typically requires a very
high breakdown field value, greater than 2*10.sup.9 V/m, for
auto-electronic emission (eg in a VAD). Disregarding
momentarily the fact that the PAGD has a positive I/V.sup.2
slope and taking its cathode- or anode-supplied voltage
intercepts (0.0005 and 0.00005, respectively) to calculate
the field-enhancement factor .beta. required by the
field-emission theory to explain the unpredicted
auto-electronic emissions observed in the PAGD regime, we
end up with .beta. values of the order of 10.sup.6 to
10.sup.7 (for actual fields of 15,000 V/m), if we were to
assume, incorrectly, that the long gap PAGD operates like a
(short-gap) VAD. Indeed, what is remarkable about the PAGD
regime in these reactors is the very low (>10.sup.5 -fold
lower) values of the fields required for the PAGD
transduction of high current densities, a phenomenon that
actually occurs during known VAD regimes (cold cathode or
thermionic), but typically only at 10.sup.2 -fold lower
values than those required and predicted by the
field-emission theory (Farrail, G. A. (1980) "Electrical
breakdown in vacuum", in `Vacuum arcs, theory and
application`, Lafferty, J. M., ed , p 20 & f, J. Wiley
& Sons, N.Y., N.Y.).
Pulse Input Energy
Pulse input energy was determined for a
variety of conditions (pressure, gap, electrode area,
residual gas, input current and input voltage, duration of
input pulse, cathode material, etc) and typical examples are
presented in Table 13. In the PAGD regime, input pulse
duration and corresponding duty cycle are self-regulated
events dependent upon the frequency controlling factors
already discussed, and thus the input pulse times shown in
Table 13 are spontaneous and not externally determined, as
would be the case for interrupted vacuum-arc discharges
(IVADs). As a function of the input power characteristics,
input energy per pulse in the PAGD regime ranged from as low
as 1 mJ to >112 J (Table 13). Values as high as 250
J/PAGD input energy have been determined without slippage to
a VAD regime for typical 5-8 cm gap, 4 to 128 cm.sup.2 plate
reactors. Under the same conditions, higher values will
promote slippage of the PAGD into the VAD regime. However,
higher values should be possible with still larger electrode
spacing and higher input currents (eg 4 to 10 A).
Reactor Pulse Energy
Typical input, reactor and output energies per
pulse, respectively, columns A to C, ordered vertically by
increasing input energy, are shown in Table 14. The data was
obtained with plate reactors of 4 to 128 cm.sup.2 cathode
areas, gaps of 5 to 8 cm, at different pressures (in air or
argon) and PPS rates of 0.1 to 110 (column D, Table 14). Two
separate types of associated circuits were utilized to
measure the output energy per pulse (column C, Table 14):
1) In a double diode configuration,
oscillographic reactor measurements for groups 1 to 3, Table
6, were taken at the junctions of the cathodes with
capacitors 10a and 10b (FIG. 21A), and at the junction of
the axial anode with another capacitor placed prior to the
center tap of transformer 26, in series with both parallel
capacitors 10a and 10b. Coils 26a and 26b of transformer 26
were replaced by a third series capacitor intermediate
parallel capacitors 10a and 10b, and oscillographic AC
output readings taken across this capacitor (groups 1 to 3,
Table 14); the total series capacitance was 5.3 .mu.F.
2) In a single diode configuration,
oscillographic reactor measurements for groups 4 to 14,
Table 6, were taken at the junctions of the cathode with
capacitor C3, and of the anode with capacitor C5 (see FIG. 9
of our copending U.S. application No. 08/054,111 entitled
"Energy Conversion System"), and oscillographic or long-term
DC output readings were determined at the input to the
battery pack CP; the C3/C5 series capacitance was 17.5 mF.
Two conclusions, independently from all other
varying conditions, may be taken from the data of Table 14:
the pulse energy released within the reactor varies from
<3 to >50.times. the input energy per pulse (column A
vs columns B and C); and, in general, the reactor energy
varies inversely to the pulse frequency (columns B and C, vs
column D). In other experiments, reactor energies per pulse
have been observed to reach >500 J. Given that the
reactor pulse voltage (Vp) is determined by the extinction
voltage Vx (Vp=Vb-Vx) and thus cannot reach the amplitude of
the breakdown voltage Vb, this involution of energy observed
per pulse in the reactor and at its output indicates that it
is a current amplification phenomenon. Indeed, with input
currents of 1.2 to 1.7 A and input pulse energies of 1 to 30
J, peak pulse reactor currents have been observed to reach
>150 A.
Dynamic Capacitance of PAGD Reactors
The static capacitance of typical reactors has
been discussed in Example 6. A typical 128 cm.sup.2 plate
reactor would have a capacitance of the order of 2 pF, and
at an applied 560 V potential, be capable of storing 0.3
micro-Joules, an infinitesimal quantity of energy (E=0.5 C
V.sup.2, where E is in Joules, C in Farads and V in Volts).
With a typical pulse input energy injection of 5 to 15 J,
the reactor will develop 25 to >400 J per pulse; under
these conditions at pulse reactor voltages (Vp) of 100 to
500, the dynamic capacitance of the discharge tube will
range from 0.2 to 80 mF.
Anomalous Reaction Forces in the PAGD Regime
Determinations of the anomalous cathode
reaction forces in the PAGD regime was carried out utilizing
the reactor pulse energy or the pulse output energy,
together with the metallographic data or by measuring the
force in a reaction balance. The kinetic energy of each
pulse was determined either directly, by integration of
oscilloscopic pulse profiles, or indirectly, by long-term
resistive discharge measurements of the batteries storing
output power. The cathode material utilized for these
experiments had a density of 1.86 g/cm.sup.3. For a mean net
pulse output energy of 86.4 J (Net energy out=output reactor
energy-input reactor energy), or 24 mWh, and a mean volume
of cathode metal ejected of the order of 3.1*10.sup.-8
cm.sup.3, a single PAGD releases 5.8*10.sup.-8 g of metal in
40 to 50 msec, or 1.3*10.sup.15 Al ions. Accordingly, the
calculated kinetic energy of each Al ion leaving the cathode
is quite high, of the order of 4.8*10.sup.5 eV, more than
three orders of magnitude that typically found in VADs
(Tanberg, R (1930) "On the cathode of an arc drawn in
vacuum", Phys Rev, 35:1080; Kobel, E (1930) "Pressure and
high vapour jets at the cathodes of a mercury vacuum arc",
Phys Rev, 36:707; Plyutto, A. A. et al (1965) "High speed
plasma streams in vacuum arcs", Sov Phys J Exp Theor Phys,
20:328). Under these conditions of PAGD production and
measurement, the energy density of the Al cathode being
operated in a PAGD reactor, is of the order of 2.8*10.sup.9
J/cm.sup.3, only three orders of magnitude less than the
energy density value of the energy priming the vacuum, as
calculated by Aspden ("Gravitation", 1975 p.61).
Corresponding rms vapor velocity of the ejected Al ions was
1.7*10.sup.8 cm/sec. Utilizing Tanberg's formula for the
reaction force F.sub.R in dynes (F.sub.R =m*V/1.39), such a
typical PAGD deploys an anomalous reaction force of 143.6
dynes. Determination of the anomalous ion force by reaction
weight measurement, under similar conditions, yielded 245.2
dynes. Anomalous cathode reaction forces >300 dynes have
been observed in other PAGD experiments (with pulse output
energies of 25 to >100 mWh).
In referring to the anomalous reaction forces
present in VADs (Tanberg's and Kobel's work), Aspden has
suggested a proportionality of the order of 100*i.sup.2
(where i is input current in real units), for the
electrodynamic action observed in these experiments (Aspden,
H (1969) "The law of electrodynamics", J Franklin Inst,
287:197). Graneau et al (Graneau, P & Graneau, P. N.
(1985) "Electrodynamic explosions in liquids", Appl Phys
Lett, 46:470; Azevedo, R et al (1986) "Powerful water-plasma
explosions", Phys Lett A, 117:101), in their calculation of
the average acceleration force for water-plasma arcs
(F.sub.av =(.mu..sub.o /4.pi.)(k*i.sup.2), where .mu..sub.o
is the permeability constant of the vacuum in Henrys per
meter, and the force is in Newtons) have utilized k as a
figure of merit for the strength of the explosions observed.
As may be seen from Table 15, the k values of the PAGD are
very high (100.times. higher than those observed in VAD
studies, compare VAD groups 1 to 3 with PAGD groups 6 and 7,
Table 15), and are comparable to those calculated by Graneau
et al for water-plasma arc explosions. Yet, the PAGD input
current values are the lowest of all groups. Following
Aspden's interpretation of the law of electrodynamic action,
the PAGD k values are found to be in the range prescribed by
the ion/electron mass differential for Al ions (49,185),
which lies in the 10.sup.4 range.
Work-function of Cathode Material
Based upon data for the PAGD performance of
diverse cathode materials presented above in Table 8,
together with Pauling's tabulation of element
electronegativities (Electronegativity X=0.44o-0.15, where o
is the work-function of the element (Lange's Handbook of
Chemistry", 1979 McGraw-Hill Book Co, N.Y., N.Y., p 3-11)),
we determined the PAGD affinity of diverse cathodes to
decrease with increasing element electronegativity (C) and
cathode work-function (o), as shown in Table 16. The lower
the work-function of the cathode metal utilized, the greater
is the observed PAGD affinity. It is expected that materials
with work-functions of <1.5, such as Li, Be, Mg, Cs, etc,
will support PAGD production better than Al does. Tungsten
(W) was the only material tested not in plates but in thin
rods. No correlation of PAGD production affinity with any
other physical parameters considered (eg atomic electron
affinities, ionization potentials, atomic weight, density,
melting and boiling points, thermal conductivity and
electrical resistivity) was found, except that the two best
PAGD cathode emitters had the lowest melting points and
densities of all cathodes examined.
Typical Expected Cathode Lifetimes
Utilizing plates composed of either hardened
aluminum or Alzak material with 3 mm of thickness, and thus
with a volume of 38.4 cm.sup.3 per plate and considering
that only 2/3rds of the cathode shall be used (a 2 mm layer
out of the 3 mm thickness), the total number of pulses per
plate total (TLT) and partial (PLT) lifetimes is
theoretically:
1--Alzak: TLT: 6.2*10.sup.7 pulses; PLT:
4.1*10.sup.7 pulses;
2--H34: TLT: 1.2*10.sup.9 pulses; PLT:
8.1*10.sup.8 pulses;
Typically, a H34 device can produce about 0.25
kWh per 10,000 pulses. The corresponding value for a PLT is
thus a minimum of 1.0 MWh/Alzak cathode and of 20 MWh/H34
cathode. As the cathode for each combination is only 66.7%
consumed, the vacuum pulse generator may continue to be used
in a reverse configuration, by utilizing the other plate in
turn as the cathode; thus, the minimal values become,
respectively, 2.0 MWh/Alzak pulse generator and 40 MWh/H34
pulse generator. The same rationale applies if the
configuration utilized was that of the double diode.
A summary of the typical specifications of
PAGD reactors is presented in Table 17, though its values
should not be construed as limits to the phenomenon such as
it might manifest itself in other conditions.
Unlike other discharge tubes in prior art (eg
Manuel, U.S. Pat. No. 3,471,316; Boetcher, U.S. Pat. No.
3,663,855; Conrad, U.S. Pat. No. 4,764,394; Alexandrovich,
et al, U.S. Pat. No. 3,821,580; Dethlefsen, U.S. Pat. No.
5,126,638), which must be triggered by an external pulse
generator, the PAGD reactor is the oscillator component in
any of the pulse generator circuits discussed. Essentially,
the PAGD reactor is a low breakdown field oscillator that
does not require a trigger electrode, nor any external
shaping of the applied current or voltage, which is simply
DC. In distinction from the externally pulsed abnormal glow
discharge described by Manuel in U.S. Pat. No. 3,471,316,
the PAGD regime is a self-pulsed or self-generated, and
self-regulated discharge method. In fact, with the
appropriate input resistance, a PAGD reactor, as described,
will operate in the PAGD regime autogenously, in the absence
of any parallel capacitance, and utilizing a battery pack as
a power source. This application describes the physical and
operational parameters necessary to configure a vacuum
discharge tube to elicit self-generating discharges, and
thus be self-pulsed, in the PAGD plasma regime, directly
from a direct current supply.
Unlike prior art glow discharge tubes that are
fundamentally flash over devices that do not employ any form
of emission (eg Manuel, U.S. Pat. No. 3,471,316; Conrad,
U.S. Pat. No. 4,764,394), the discharge has both a glow and
auto-electronic emission components. Unlike VAD tubes (eg
Boetcher, U.S. Pat. No. 3,663,855; Alexandrovich, et al,
U.S. Pat. No. 3,821,580), the cold cathode PAGD
auto-electronic emission pulse is not triggered externally,
but a spontaneous occurrence observed at low breakdown
fields, with emitter current densities 10 to 1000.times.
lower than those required by the Fowler-Nordheim theory for
field emission.
As already observed in prior art VAD devices
(eg Tanberg's or Kobel's papers referenced above), anomalous
cathode reaction forces are set up in the PAGD reactors;
however, with input currents one or two orders of magnitude
less than needed for a VAD, the PAGD-associated reaction
forces manifest a proportionality constant that is 10 to 100
times higher than found for VADS (10.sup.3 to 10.sup.4
*i.sup.2 vs 10.sup.2 *i.sup.2). These forces may account for
the low input current densities observed in the PAGD regime.
Evidently, as with the PAGD regime itself, these reaction
forces result from the specific physical and operational
parameters employed, amongst which the large gaps, large
electrode areas, cold cathode status, cathode low worth
function and low breakdown fields figure prominently.
TABLE
9
__________________________________________________________________________
A B C
D
F G
W L Plate
Area
E d p
No. (cm) (cm) (K.sub.L)
(cm.sup.2)
K.sub.A
(cm)
(Torr)
__________________________________________________________________________
1 16
4 1 64
1 3.6 2.8 * 10.sup.6
2 32
4 1.41 128 2
5 2.0 * 10.sup.6
3 32
8 1.41 256 2
7 1.4 * 10.sup.6
4 16
4 1 64
1 5 2 * 10.sup.6
5 32
4 1.41 128 2
5 2 * 10.sup.6
6 32
8 1.41 256 2
5 2 * 10.sup.6
__________________________________________________________________________
H
I
K
M O
J (plate)
J
(plate)
I
J/p.sup.2
L
J (plate)
N
J/p.sup.2
(A/m.sup.2)
Exptl
J/p.sup.2
Exptl
J
(plate)
Exptl
J/p.sup.2
Exptl
No.
Predic
@
Vb Predict
@
Vb (A/m.sup.2)
@
max
Predict
@
max
__________________________________________________________________________
1 17.7 0 2.2 *
10.sup.12
0
41.4 0 5.2 * 10.sup.13
0
2 8.8 8.8 2.2 *
10.sup.12
2.2
* 10.sup.12
20.7
20.7 5.2 * 10.sup.12
5.2
.times. 10.sup.12
3 4.4 ND 2.2 *
10.sup.12
ND
10.35
ND
5.2 * 10.sup.12
ND
4 17.7 0 4.4 *
10.sup.12
0
41.4 0 1.4 * 10.sup.13
0
5 8.8 8.8 2.2 *
10.sup.12
2.2
* 10.sup.12
20.7
20.7 5.2 * 10.sup.12
5.2
.times. 10.sup.12
6 4.4 4.38 1.1 * 10.sup.12
1.1
* 10.sup.12
10.35
19.53
2.6
* 10.sup.12
4.9
.times. 10.sup.12
__________________________________________________________________________
NA = Not Applicable
ND = Not Determined
TABLE
10
______________________________________
A
B
C2
Area
I rms J (plate)
No.
(cm.sup.2) Input (A/m.sup.2)
______________________________________
1
256
1.7 66.4
2
128
0.001 0.078
3
128
0.112 7.8
4
128
2.0 156.25
5
64
2.0 312.5
6
16
2.0 1,250
7
4
2.0 5,000
______________________________________
TABLE
11
__________________________________________________________________________
C
B X-section
D
E
A I rms
area
of
Uncorr
Emission
G
Area
Input
plasma
ball
J
(em)
E
area J (em)
H
No.
(cm.sup.2)
(A) (cm.sup.2)
(A/m.sup.2)
Method
(cm.sup.2)
(A/m.sup.2)
Method
__________________________________________________________________________
1 256 0.500
0.0333
1.2
* 10.sup.5
Videog;
4.4
* 10.sup.-4
9
* 10.sup.6
Videog;
uncorr
corr
2 128 0.119
0.0095
1.25
* 10.sup.5
Videog;
1.3
* 10.sup.-4
9.5
* 10.sup.6
Videog;
uncorr
corr
3 128 0.265
0.0177
1.5
* 10.sup.5
Videog;
2.4
* 10.sup.-4
1.1
* 10.sup.7
Videog;
uncorr
corr
4 128 0.500
0.038
1.3 * 10.sup.5
Videog;
5.1
* 10.sup.-4
9.8
* 10.sup.6
Videog;
uncorr
corr
5 128 1.030
0.0303
3.4
* 10.sup.5
Videog;
4.4
* 10.sup.-4
2.6
* 10.sup.7
Videog;
uncorr
corr
6 128 0.500
0.044
1.1 * 10.sup.5
NA
5.9 * 10.sup.-4
8.5
* 10.sup.6
Videog;
corr
7 128 0.500
ND
NA NA 1.04 * 10.sup.-4
4.8
* 107
Metallog
8 128 0.100
ND
NA NA 3 *
10.sup.-4
3.3
* 10.sup.6
Metallog
9 128 0.500
ND
NA NA 6.2 * 10.sup.-4
6.5
* 10.sup.6
Metallog
__________________________________________________________________________
TABLE
12
__________________________________________________________________________
A B
C
D
F
H
Area
Gap
Vb
E @ Vb
E
Residual
G
Cathode
No.
(cm.sup.2)
(cm)
(Volts)
(V/m)
Torr
Gas Status material
__________________________________________________________________________
1 256 5 278 5,560
2
* 10.sup.-6
Ar
Sealed H.Al.
2 128 5 774 15,480
2
* 10.sup.-6
Ar
Sealed H.Al.
3 128 5 3500
70,000
6
* 10.sup.-4
Ar
Rotary Pump
H.Al.
4 128 5 1600
32,000
9
* 10.sup.-4
Ar
Rotary Pump
H.Al.
5 128 5 560 12,200
4
* 10.sup.-3
Ar
Rotary Pump
H.Al.
6 128 5 300 6,000
8
* 10.sup.-2
Ar
Rotary Pump
H.Al.
7 128 5.5
1350
24,545
1
* 10.sup.-3
Ar
Rotary Pump
H.Al.
8 16 4 560 14,000
5
* 10.sup.-2
Ar
Rotary Pump
H.Al.
9 4 8 560
7,000
2
* 10.sup.-1
Ar
Rotary Pump
H.Al.
10 10 9 900 10,000
1
* 10.sup.-4
Air
Sealed Ni
11 10 18 1500
8,333
1
* 10.sup.-4
Air
Sealed Ni
__________________________________________________________________________
TABLE
13
______________________________________
D
B
C
Input
Input
Pulse Energy
A
Current Time per Pulse
No.
Volts
(A) (msec)
(Joules)
______________________________________
1
3,500 0.010
0.5 1.8 * 10.sup.-2
2
1,020 0.001
1 1 * 10.sup.-3
3
600
0.100
6 3.6 * 10.sup.-1
4
560
0.500
20 5.60
5
560
1.700
3 2.85
6
560
1.700
30 28.56
7
560
1.200
48 32.26
8
560
4.000
50 112.00
9
250
0.500
80 10
10
250
1.100
20 5.5
______________________________________
TABLE
14
______________________________________
A
B
C
Input
Reactor Output
Energy
Energy Energy
per
pulse
per
pulse per pulse
D
No.
(Joules) (Joules) (Joules)
PPS
______________________________________
1
0.1
0.3/0.5 0.16/0.2
60
2
0.33
1
1 60
3
0.38
2
2 60
4
1.84
ND
2.8 110
5
2
ND
121 0.2
6
4.3
ND
20.2 8
7
5.6
ND
154.5 0.2
8
6.5
367.7 353.8 0.2
9
8
71.5 25.2 1
10
14.4
ND
99 1
11
22.2
ND
72.9 0.8
12
26.8
ND
50 8
13
38.2
ND
80.3 1.5
14
44.8
261.5 253.5 0.3
______________________________________
TABLE
15
__________________________________________________________________________
A C
Current i
B
F.sub.R
D
E F G
No.
in A i.sup.2
in
dynes
ki.sup.2
k
Proportionality
Source
__________________________________________________________________________
1 16 256 258.6
25,800
100.8
10.sup.2
i.sup.2
Tanberg
2 19 361 356.1
35,609
98.6
10.sup.2 i.sup.2
Tanberg
3 35 1,225
1,470
147,000
120
10.sup.2 i.sup.2
Kobel
4 12,700
1.6
* 10.sup.8
0.9
* 10.sup.11
9.4
* 10.sup.11
5.8
* 10.sup.3
5
* 10.sup.3 i.sup.2
Graneau
5 25,400
6.5
* 10.sup.8
4.3
* 10.sup.10
4.3
* 10.sup.12
6.6
* 10.sup.3
7
* 10.sup.3 i.sup.2
Graneau
6 1.6 2.56 143.6
14,359
5.6
* 10.sup.3
6
* 10.sup.3 i.sup.2
PAGD
7 1.6 2.56 245.2
24,516
9.6
* 10.sup.3
10.sup.4
i.sup.2
PAGD
__________________________________________________________________________
TABLE
16
______________________________________
B
C
D
relative
Electro- Work
A
PAGD negativity function
.phi.
No. Element
affinity X = 0.44.phi. - 0.15
(eV)
______________________________________
1
Al
+++++
1.5 3.75
2
Zn
+++++
1.6 3.98
3
W
++++
1.7 4.20
4
Ni
++++
1.8 4.43
5
Fe
++++
1.8 4.43
6
Ag
+++
1.9 4.66
7
Cu
+ Cu (I) 1.9
4.66
Cu
(II) 2.2
4.89
______________________________________
TABLE
17
______________________________________
Gas
fill
Air,
Nitrogen, Inert gas
Gas pressure, Torr 1 to
10.sup.-6
Interelectrode distance
2.0
to >20 cm
Electrode Geometry
Planar-parallel, hemi-
cylindrical
and co-axial
Cathode
area >2
cm.sup.2
Electronegativity of cathode material
<1.0
to 2.2
Cathode work-function
<3.5
to 5.6 eV
Breakdown voltage 200
to 5,000 V
Breakdown fields
2,500 to >50,000
Current consumption 1 mA to >4A
(in the
PAGD
regime)
Peak reactor current 1 mA to >250 A
Current density (cathode area)
0.05
to 5,000 A/m.sup.2
Current density (emission site)
10.sup.5
to 5 * 10.sup.7 A/m.sup.2
as a function of input power
PAGD
rate
0.01 to >50,000 PPS
Duty
cycle
1 to >40%
Pulse
Time
0.1 msec to 100 msec
Input energy per pulse
10.sup.-3
to >2 * 10.sup.2 J
Reaction energy per pulse (@ reactor)
<1
to >5 * 10.sup.2 J
ReactorDynamic Capacitance
100
.mu.F to >80 mF
