Amperex Model 120NB End Window GM (1950s, 1960s)
This rather large end window GM tube was manufactured by Amperex Electronic Corporation of Brooklyn New York. Its main purpose would have been to count beta particles—the window is sufficiently thick that it would not respond to alpha particles. I believe that the N in the model number refers to the use of a neon fill gas and that the B refers to the four pin base.
Size: 5.75” long and 2.312” diameter
Window: 1.906" effective diameter, 5.6 mg/cm²
Operating voltage: 900 volts
Dead time: ca. 300 usec
Cathode: Stainless steel coated on outside with plastic.
Gas: Neon, halogen quenched
Base: Four prong
- Atomic Energy Commission Radiation Instrument Catalog, Date July 1, 1950, page BG-1A11A.
- Amperex Nuclear Products catalog of radiation tubes, 1981.