Technical Associates Models TA-B1 and TA-B3 Thin Wall GMs (ca. early 1950s)
These glass-walled GM tubes were probably manufactured by Technical Associates of Glendale California in the early 1950s. Although the tube on the right has no markings on it that would help identify the manufacturer, it came with the Technical Associates Model TA-B1 (on the left side of the photo) and its dimensions and appearance are identical to those of the Technical Associates Model TA-B3.
Both of these tubes can be considered thin walled beta counters. Since they are photosensitive, they would need to be operated in a light tight enclosure. The major difference between the two is that the electrical connection to the cathode in the Model TA-B1 is via a short side arm projection on the glass wall. In the Model TA-B3, the cathode connection is at the end of the tube adjacent to the anode connection. Otherwise, their specifications are identical.
Size: 7" long, 3/4" diameter
Wall: Glass, 30 mg/cm²
Cathode: Inner surface of glass wall coated with silver
Operating voltage: 1400-1600 volts
Gas: Tetramethyllead vapor
AEC Radiation Instrument Catalog, page date July 1, 1950.