A p-n Junction Photovoltaic Detector for Use in Radiotherapy

A radiation detector in the form of a shielded p-n junction is described. The junction with the appropriate shielding is quality independent over the range 0·8 to 14 mm cu H.V.T. to better than 10%, and, with the instrumentation described, the output voltage is proportional to the incident dose rate (to within 5%) over the range 0·3 to 750 r/min. Also described are the temperature and polar responses, as well as measurement of radiation damage from 60 Co γ-rays. A comparison is made between the p-n junction detector and a cadmium sulphide probe. The development of probes of smaller physical dimensions and to measure lower dose-rates, is discussed.