Prototype ORNL Beta Dosimeters (early 1950s)
The pocket chambers and 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 wall of these dosimeters was 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 these particular dosimeters other than the fact that they came from Oak Ridge National Laboratory and were stored together with other similar dosimeters. The latter are well documented and date from 1953. My guess is that the instrument development people were looking for a way to provide structural integrity to thin paper (or plastic) walled chambers without having to resort to the outer perforated wall used in the other previously mentioned dosimeters. Of the two devices shown side by side in the photograph to the left, one has a black conductive paper wall and the other has a wall of clear plastic. I suspect that the latter was a demonstration unit and that it used a plastic window so that the interior components could be seen. It is hard to see, but there is a thin central electrode (graphite?) running up the center of the chamber. The wall shape is maintained by a rib-like structure consisting of four "D-shaped" plates. The photo to the right shows the back of the paper-walled chamber. The aluminum charging contacts projecting from the bottom of these dosimeters came from standard Victoreen pocket chambers.
To the best of my knowledge, they never went into routine use at the lab.
Size: 1 3/4” x 1 1/8” exclusive of charging contact
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.