Paper Walled Beta Wrist Dosimeter from ORNL (1950s)
The indirect reading pocket dosimeters of the 1940s and 1950s were designed for providing convenient measurements of worker exposures to gamma rays and X-rays. Nevertheless, it was recognized that the beta dose to the skin, which could be significant, was not being indicated because the chamber walls were sufficiently thick to completely stop beta particles under 1 MeV or so. In 1953, Oak Ridge National Laboratory tried to solve this problem by the use of beta-sensitive thin-walled dosimeters. The chamber walls of these dosimeters were made from electrically conductive paper 7 mg/cm2 in thickness. This thickness corresponds to the depth of the germinal layer of skin, the tissue of concern.
I have no specific information about this particular wrist dosimeter other than the fact that it came from Oak Ridge National Laboratory and was stored together with other prototype paper-walled dosimeters. The latter are well documented and date from 1953. I assume that this wrist badge was built sometime later, probably the mid to late 1950s. It was probably intended to be used to estimate the dose to the hands of workers who were handling sources. Nevertheless, to the best of my knowledge, it never went into routine use.
The black paper wall is protected from damage with an outer plastic cage (1 1/2" diameter and 3/8" thick). The plastic is thick enough to stop all but the higher energy betas. In general, the betas either reach the chamber wall unimpeded or they are completely stopped by the plastic.
As seen in the photograph above right, the chamber can be unscrewed from the holder on the wrist band. The charging contact is recessed in the small circular hole seen on the backside of the chamber. There is no easy way to determine the shape of the anode without tearing it apart.
Donated by Oak Ridge National Laboratory.
- Gupton, E.D., Pocket Covered Pocket Dosimeter, Oak Ridge National Laboratory, Inter-company Correspondence. Nov. 11, 1953.
- Hubbell, H.H., Johnson, R.M., and Birkhoff, R.D., Beta-sensitive personnel dosimeter. Nucleonics, February 1957, p. 85.