Tracerlab TGC-1 and TGC-2 End Window GM Tubes

The TGC-1 and TGC-2 are glass walled end window GM tubes designed for beta counting. They were the first GM tubes produced by Tracerlab, Inc. The earliest references I have for them are June 1948, while the last reference is 1958. TGC, as might be expected, stands for Tracerlab Geiger Counter.

The key difference between the two tubes is that the TGC-1 has a 3-4 mg/cm² mica window while the window of the TGC-2 is < 2 mg/cm². Due to its thinner window, the TGC-2 was capable of alpha detection and had a better efficiency for low energy betas. Both employed helium as the fill gas together with an organic quench gas.

Tracer TGC 2 GM Tube
Tracer TGC 1 GM Tube

Size: 3.75” long and 1.5” inner diameter

Window thickness:

  • TGC-1: 3-4 mg/cm²
  • TGC-2: 1.5 mg/cm²

Wall: Glass, > 300 mg/cm², aquadagged on inside

Anode: Tungsten central wire

Operating voltage: 1400 V

Plateau length: 300 volts

Fill gas: Helium

Fill gas pressure: 720 mm Hg

Dead time: ca. 200 us

Base: Four prong ceramic base


  • TGC-1: $50 in 1948, $43.50 in 1952
  • TGC-2: $75 in 1948, $53.50 in 1952


  • Nucleonics June 1948 p 80.
  • Nucleonics June 1948 p 103.
  • AEC Radiation Instrument Catalog, page date May 1, 1950.
  • Tracerlog No. 11 June 1948.
  • Tracerlab Inc, Catalog E, March 1958.