Understanding Neutron Radiography Post Exam Reading VIII-Part 2a of 2A

Pocket dosimeters tended to be slightly larger than pocket chambers. Their
walls might be made of aluminum, bakelite, or some other type of plastic. If
the material was not conductive, the inner surface of the chamber was coated
with Aquadag (graphite). The central electrode was usually a phosphor
bronze rod. This made pocket dosimeters more energy dependent than
pocket chambers whose central electrodes were usually aluminum. Some
dosimeters (e.g., Keleket Model K-145) employed boron-lined chambers
which made them sensitive to thermal neutrons.
Pocket dosimeters must be charged (ca. 150 ~ 200 volts) with some sort of
charger, but they do not require another device to read them. This allows the
worker to determine his or her exposure at any time, an important advantage
when working in high radiation fields.
The first direct reading pocket dosimeters were built by Charlie Lauritsen at
the California Institute of Technology.
Charlie Chong/ Fion Zhang
http://www.orau.org/ptp/collection/dosimeters/pocketchamdos.htm