20th Century Electronics GM Tube  (late 1950s, 1960s)


This particular tube, a Model B12H, was manufactured by 20th Century Electronics of New Addington, England.  They are now known as Centronic and are located in Croydon, a suburb of London.

The original glass wall was broken - that seen in the photograph is simply a replacement.  What is most unusual about this tube is the configuration of the cathode, a spiral wire supported on the outside by three wires.

Operating Voltage: 370 volts

Plateau length: 100 volts.

Sensitivity: 5600 cpm/mR/hr

Size:  ca. 7 1/2" long,  3/4" diameter

Wall: glass



Donated by Dave Allard

I am grateful to Prof. Jean-Francois Loude who provided the technical information about this tube.

GM Detectors             Museum Directory

Last updated: 07/25/07
Copyright 1999, Oak Ridge Associated Universities