Characteristics of a radiation-charged electret dosimeter

The radiation-charged electret ionization-chamber uses an electret formed in situ by applying a bias voltage to the chamber electrodes while the chamber is being irradiated with X-rays. An electrometer permits measurement of the charge on the electret surface before and after the use of the chamber as a dosimeter. The authors present measurements of dosimeter range, sensitivity, and energy dependence as functions of bias potential, electrode separation, guard-ring size, and various materials. Reproducibility permits detection as low as 55 μGys with range up to 100´s of cGys depending on the design of the chamber, with charge retention properties similar to those of electrets formed from corona discharge