Model 440 Radiac Ion Chamber (1970s)
This ion chamber is a little bit of a mystery. The 1975 List of Radiacs in the Navy Program and the 1987 List of Military and Civil Defense Radiac Devices seem to indicate that the 440 was only manufactured by the Victoreen Corporation. Nevertheless, this example was manufactured by the Heat Pipe Corporation of America (of Whippany New Jersey ). Not one of your better known manufacturers of radiological instrumentation. A couple of features about the manufacturer's identification plate on the side of the instrument seem to indicate it was part of a very limited run. First, the “440” seems to be some sort of rub-on that is protected by scotch tape. Second, the serial number (SN 0026) is written in pen. The National Stock Number, 6665-00-938-6806, is the correct number for the 440.
The two previously mentioned references state that the 440 had an upper range of 300 R/hr. This is a mistake. The Victoreen 440 and this version of the 440 both read up to 300 mR/hr, not 300 R/hr.
Since the front end of the ion chamber has a very thin aluminized window, it is capable of responding to alpha and beta particles as well as gamma rays. Nevertheless, it was only calibrated for gamma rays.
Ranges: 0-3, 0-10, 0-30, 0-100 and 0-300 mR/hr
Case size: 4.25” x 7.5” x 4.5”
Chamber: 2.5” long, 3.5” diameter
Batteries: Four 1.5 volt “D cells”
A sticker on the end of the instrument reads June 1977.
- Naval Electronic Systems Command List of Radiacs in the Navy Program P-9670-1, February 1975.
- Defense Nuclear Agency List of Military and Civil Defense Radiac Devices HQDNA (AR) 3M Revised, August 1987.