Raytheon Model CK 1020 and 1021 GM Tubes (ca. early 1950s)

Raytheon 1020 1021 GM Tubes

The Models CK 1020 and 1021 are nearly identical thin wall beta-gamma GM tubes manufactured by Raytheon Manufacturing Company of Newton, Massachusetts. The only difference between the two is size: the 1020 is 3/4" longer than the 1021. In the photo, the tubes on the left and in the center are Model 1020s. The tube on the right is a 1021. Because the tubes are light sensitive, they are painted black. For fun, I removed the paint from the top end of the tube in the center of the photograph. As such, the end of the cathode, a thin coating of aquadag on the inside of the glass, is visible.


  • CK 1020 - 6" long, 3/4" diameter
  • CK 1021 - 5 1/4" long, 21/32" diameter

Wall: Glass, 35 mg/cm²

Cathode: Inner surface of glass wall coated with aquadag (3" for 1020 and 2.5" for 1021)

Operating voltage: 850-950 volts

Gas: Organic quenched

Donated by Ron Kathren.


  • AEC Radiation Instrument Catalog, page date July 1, 1950.
  • Nucleonics May 1949, page 96.
  • Nucleonics April 1954, back cover.
  • Raytheon technical specifications sheet.