Gregory Hodowanec: Cosmology Notes (12-1-91) Gravity Signal Astronomy with the Rustrak 288

The basic GW detector unit, #75, as described in the January 1989 issue of R-E’s Electronic Experimenter handbook, is generally used in a linear mode of operation, with a rather fast moving chart recorder speed on a typical pen-type chart recorder. In the gravimeter mode, the various cosmic signals, e.g., the density "shadows" of distant masses, or the "impulses" of the more distant cosmic events, show up as "modulations" of the earth gravity field as measured at the site of the detection unit. On the moving chart paper these signals would appear as "wiggles" above and below the average value of the g-field and thus as variations in the dc levels of the detector output. These responses reveal the presence of novae, supernovae, galaxy structures, black holes, etc., as is described in the many simple articles by the writer.

Bill Ramsay reported to me in August that in a special experiment he undertook where he coupled a type #75 detector to a Rustrak 288 recorder unit, he serendipitously noticed many "embedded forms" in the scatter plot of the data points as recorded by the general system shown in Figure (1). The writer has since obtained a Rustrak 288 unit (courtesy of Bill Pendergast) and was able to verify the embedded forms seen by Bill Ramsay. To this writer, however, the forms appeared to be very similar to the images of the large and superclusters of galaxies as was noted by the optical astronomers. Therefore, an attempt was made to understand how the system of Figure (1) could result in what appeared to be very much a two-dimensional image of a small sector of our universe as "drift scanned" by the rotation of the earth. This Note will report on some of these thoughts.

Figure (1a): Basic system used for scan of Figure (4a). For this test, Rin in the #75 GW detector was set to 0 ohms. The LP filter has a cutoff ~ 10 Hz. The Rustrak 288 is essentially a 0-100 mV meter. The GW #75 uses a bipolar transistor (1458) with a 9 volt supply.

Figure (1b): Basic system used for the scan of Figure (4b). For this test, Rin in #130A GW detector was 75 ohms. The LP filter was cut off at ~ 10 Hz. The Rustrak 288 remains a 0-100 mV meter. The IC in the GW #130A was an ICL 7621 with a 1.5 volt supply.

Figure (1c): Basic system used for scan of Figure (4c). For this test R_in remained 75 ohms. The LP filter is two-stage with cut-off less than 1 Hz. The Rustrak is a 0-1 V meter now. The system is now responding to more "local" supercluster?

These rugged little units are relatively low cost and had served many monitoring applications in the past. Thus many units are still available at small cost ($20-40) in some surplus outlets. Many are used by amateurs in radio astronomy applications. They are also useful in this application --- at least for the early stages of development.

The typical Rustrak unit is simply a 1 mA meter movement in which the needle pointer is free to move as in any other D’Arsonval meter movement. There is no friction as seen in some pen-type recorder units. The typical Rustrak unit has a chart speed of 1/2" or 1" per hour, a very slow chart speed. The chart drive motor also drives a nylon gear which keeps a spring-loaded bar mechanism off the meter pointer and the chart paper until after a 2-second delay, and then allows the spring-loaded bar to "slam" the needle against a roller-backed pressure-sensitive chart paper so as to create a dot (or data point) on the chart paper. The needle position at that moment is dependent on the analog output signal from the detector section. The typical #75 GW detection circuit, using a bipolar IC, has an output on the order of 1 to 3 volts, depending on the sensitivity and gain levels. However, a diode offset section can be used to eliminate most of this dc level and thus one can look at only the dc variations, which could be in the order of 0 to 100 mV. The Rustrak meter (1 mA at 100 ohms) is used directly as a 0-100 mV meter, no multiplying resistor is needed. The detector gain control may be used to center the response on the chart paper. Thus, as the chart paper moves, say at 1/2" per hour, the meter output is sampled at the 2-second rate. This creates a "scatter plot" of some 1800 data points per hour. Under these conditions there is much correlation between the GW "shadow" densities and the scatter plot of data points, giving rise to the "forms" seen in these scans. Since dense masses will tend to appear as "holes" or bare spots in the scatter plot, i.e., the images are negative, that is, the chart record high density mass as white, and low density mass as black.

Two-Dimensional Detection Process

To understand just how the Rustrak detection system may be operating, we need to review the GW detection system itself. Basically, the GW detector (the input capacitor in the #75 unit) is a scalar field detection unit. Its basic response is to the earth’s g-field at the zenith-nadir line location of the capacitor. If there were no other scalar fields present in this line other than the earth g-field, the unit would develop a constant output voltage if the g-field remained constant. However, the universe is replete with many scalar signals due to such cosmic events as novae, supernovae, as well as gravity "shadows", i.e., density variations due to the presence of massive structures in the universe. Scalar signals which are completely parallel, i.e., in a direct line with each other, will interact algebraically, e.g., increase or decrease the scalar potential, depending on the polarity of the potentials. In rhysmonic cosmology, the universe is basically Euclidian in structure, thus the scalar vectors are essentially straight-line vectors over the entire range of a finite universe. Thus those vectors will interact with the electron-ion structure of the dielectric of the detector capacitance, mainly with the ionic portion. Therefore, the variations in the g-field will result in variations in the E-field of the capacitor, and thus could be coupled out as current variations in the circuitry. In theory, this interaction would be between one g-field vector and one electron-ion pair in the capacitor. Thus the interaction "beam diameter" is basically only on the order of an atomic dimension or so, a very fine resolution, indeed. In practice, the intersection will be between may g-field vectors and many electron-ion pairs, thus the "beam size" will be due to a finite area and volume of the capacitor dielectric, but still a very, very small size. While some VLA type radio astronomy "telescopes" may be able to resolve, say a dime, at a distance of 50 miles or so, the GW "telescopes" should be able to resolve less than a pinpoint at twice the distance! Thus GW techniques may have much potential as a "new window" to the universe. The sketches of Figure (2) and Figure (3) should make these points clearer.

A simplified view of the capacitor detector is given in Figure (2). The detector capacitor here is a 2200 uF (10 volt) electrolytic capacitor having a rolled section of about 0.5" in diameter and 0.75" length. Experiments have shown that only the center portion of these capacitors are "active" in these detections, in this case about a 0.25" portion. Normally, in the linear type detections, the capacitor orientations are disregarded. However, in the Rustrak application, the capacitor is oriented with its long axis in the north-south direction. The reason for this is that the Rustrak application will not only respond to the zenith-nadir line, but also to the small angle formed by the active portion of the capacitor along the meridian position. We do not have to worry about responses along the latitude line, i.e., the east-west line, at the observing position since the earth’s rotation will effectively cancel out such responses. This will be explained in a future Note. Figure (2) is largely self-explanatory, while Figure (3) tried to give you an idea of the GW response "sector width" of the two-dimensional plots seen with this Rustrak system.

Early Rustrak System Tests ~

Many scans of the universe have been obtained by Bill Ramsay and the writer in the recent past. However, shown in Figure (4) are some scans made by the writer for this particular Note. Since they were exploratory tests, they may not be the ideal tests, but they should be able to illustrate some of the points noted here.

The scan shown in Figure (4a) was made with the system seen in Figure (1). Back-to-back diode pairs are generally used in the diode off-sets since the detectors are usually biased with dual power supply voltages and thus could have plus and minus output polarities. If the output is only a single polarity, single diodes of the proper polarity could just as well be used. In this particular test, a three diode (pair) section was used to enable an increased signal output which could be still recorded in the chart paper. The responses were with a 10 Hz LP filter and will be considered in the next section.

The scans shown in Figure (4b) and Figure (4c) were made with a MOS-type detector unit which operated at 1.5 volts. This unit had an input jack which enabled insertion of other detection capacitors (or devices) for special tests. In these two tests, a 15,000 uF 925 volt) electrolytic capacitor was used as the detection device in order to check out the theory that the "sector width" in the Rustrak system was dependent upon the length of the active portion of the detector capacitance. The 15,000 uF capacitor was approximately 1" in diameter and 2.25" in length -- giving an active length in the order of 0.75" or three times that seen with the 2200 uF capacitor. In Figure (4b), a two-section diode offset pair was used as well as a 10 Hz LP filter. In Figure (4c), the two-section diode offset was eliminated and a x2 inverting gain stage was added to drive the output levels to fill the Rustrak chart paper with responses. The LP filter was changed to 1 Hz to limit these responses to the more local cluster of galaxies. These responses are also considered next.

Figure 4a: Exploratory Scan as determined with standard GW Detector #75 & system shown in Figure (1)

The response shown in Figure (4) lead to certain conclusions.

The resolution of the Rustrak system, e.g., the size of the "embedded forms" or the universe "structures" is independent of the scan "sweep" frequencies or amplitudes, and even the chart speed, but is dependent upon the LP filtering used. As the LP filter cutoff frequency is increased, the unit will respond to the more distant universe structures, and thus show up more structures and finer details in the larger structures. However, the overall resolution is also limited by the slow sampling time of 2 seconds and the finite size of data points, the size of the Rustrak "dot".
The larger capacitor does show a wider "sector view" of the universe due to the larger active section of the capacitor, but to take advantage of this, the system gain should be able to expand this sector over the entire chart range. The scan of Figure (4b) has the wide sector width of the 15,000 uF capacitor, but the low system gain and the use of a 10 Hz filter has "compressed" all this data in but a small section of the chart. Thus the scan is very much like an overexposed photograph --- much of the data (dots) are overlapped, leading to an essentially over-scanned data plot. In Figure (4c), the sweep amplitude was increased to somewhat over the Rustrak chart size (it was preset correctly, but the amplitude increased in some way when the actual run was made). However, even here, the use of a 1 Hz LP filter illustrates very well, the somewhat larger structure sizes expected to be seen with the more "local" superclusters!

While this is a somewhat longer Cosmology note, the writer wished to present the fact that while these investigations are in their early stages, and crude at best, the potential for improvement here is enormous. While the Rustrak technique will also be much improved in the future, the writer will in the near future present some thoughts on a mechanical scanned two-dimensional system which could be adapted to an oscilloscope as a sort of "live TV" presentation. What is required here now is to get more of you independent researchers also involved here, as well as more amateur and professional optical and radio astronomers. Much is yet to be learned! Good Luck!