Tracerlab TGC-8 GM Tube |
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The TGC-8, a steel walled GM tube designed for
gamma counting, was produced by Tracerlab Inc., of Tracerlab stated that the cathode employed a large surface area plate and grid structure to maximize the tube’s sensitivity to gamma rays - a large area would increase the potential for gamma ray interactions. Tracerlab did not identify the material that the cathode was manufactured from other than to indicate that it was an alloy and a compromise between a high atomic number and the mechanical properties necessary to construct the plate and grid structure mentioned previously. When I ground open the outer steel wall of a TGC-8 and analyzed the cathode (photo below right), it turned out to be a thin sheet of tantalum. Surprisingly, there was no obvious plate and grid structure, at least in this version of the TGC-8. The tantalum cathode was simply a liner inside the outer steel wall. In the photo, a hole has been torn in the tantalum liner so that the anode can be seen. |
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When used for
measuring I-131 gamma rays, the efficiency of the TGC-8
was said to be five times that of the TGC-1 (an end window GM tube of identical
dimensions) and one third greater than a GM tube of the same size using a
bismuth cathode. |
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Size: 3.75” long and 1.5” in diameter Wall: stainless steel, > 300 mg/cm2 Anode: Tungsten central wire. Operating voltage: 950 V Plateau length: 150 volts Fill gas: helium with organic quenching agent Fill gas pressure: 800 mm Hg (The April 1952 issue of Tracerlog indicated 1450 mm Hg.) Dead time: ca. 200 us Base: four prong ceramic base: Price: $93.50 in 1952 ; |
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Nucleonics
July 1952 p 83; Tracerlab
Inc, Catalog E, March
1958; Tracerlog No. 43, April 1952; Tracerlog No. 45 September 1952 |
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