Victoreen Model VG 10A End Window GM Tubes (ca. late 1940s)
The TGC-8, a steel walled GM tube designed for gamma counting, was produced by Tracerlab Inc., of Boston Massachusetts. The earliest reference I have for the TGC-8 is the April 1952 issue of Tracerlog which notes that delivery could be expected in the Fall of 1952. The last reference I have found is 1958. TGC, as might be expected, stands for Tracerlab Geiger Counter.
The Model VG 10A end window GM detector was manufactured by the Victoreen Instrument Company of Cleveland Ohio. Like most end window GMs, it was designed for measuring the beta activity in samples that were often held in planchets positioned below the detector window. While these tubes also responded to gamma rays, their gamma efficiency was comparatively poor.
Of the two pictured here, only the one on the left has a label identifying it as the Model 10A. The other, which has no label or identification marks, is identical except for two things: it doesn't have a brass cap, and the window has a reflective coating (aluminum/steel?). This coating was probably used to prevent light from penetrating the thin mica window—the standard VG 10 tubes were photosensitive.
John Victoreen indicated that he began making end window GMs for the Manhattan District activities during WWII (BRH Vignettes of Early Radiation Workers).
Size: 4 1/4" long, 2 1/4" diameter
Window: Mica, 1 1/8" diameter, 2.9 mg/cm²
Operating voltage: 1200 volts
Gas: Argon with 8% organic vapor at 120 mm Hg
Donated by Ron Kathren.
- AEC Radiation Instrument Catalog, page date July 1, 1949, page BG-1A4C.
- Nucleonics April 1948, page 85.