Nuclear Chicago D33, D34 and D37A End Window GM Tubes (late 1950s, 1960s)

These end window GM tubes were manufactured by the Nuclear Chicago corporation of Chicago, Illinois. Prior to 1954, the company was known as the Nuclear Instrument and Chemical Corporation. The references I have date from when the company used the latter name. How the Models D-34 and D-37A differ is not known.

Nuclear Chicago GM Tubes
Nuclear Chicago GM Tubes

The photograph to the left shows, left to right: a Model D-33, a Model D-34 (cap off) and a Model D-37A (cap on). The photograph to the right shows the end windows of the same tubes. Note the circular discoloration on the end window of the D-34 tube (center) that was caused by arcing from the tip of the anode to the window.

Size: 3 3/4” long and 1 3/8” diameter

Window thickness: D-33—3.5 mg/cm² mica

  • D-34—1.4 mg/cm² mica
  • D-37A—1.4 mg/cm² mica
Wall: Stainless steel coated on the outside with plastic

Operating voltage: 900 V

Fill gas: Halogen quenched

Fill gas pressure: 100 mm Hg

Donated by Ron Kathren.


  • AEC Radiation Instrument Catalog, page date July 1, 1950, page BG-1A14.
  • AEC Radiation Measuring Instruments, Supplement for RIB-8. Page date July 1, 1954.