Application of PN junction diodes to the measurement of dose distribution of high energy radiation

Abstract

A frequently encountered limitation in the use of small ionization chambers for the continuous measurement of dose distributions in a water phantom is the unwanted current generated by cable flexing when the chamber is moved. One method of avoiding these unwanted currents is to use a pre-amplifier rigidly connected to the chamber. The difficulties can be obviated by replacing the ion chamber with a semiconductor diode, since the current induced in it by a radiation field is approximately 2*104 as great as in an ion chamber of equal volume. The use of commercially available PN junction diodes as dosimeters has been favourably reported for X-rays and for very high energy charged particles (Raju 1966, MacDougall and Robinson 1967). The purpose of this study was to evaluate the suitability of a PN junction diode as a radiation probe for an automatic isodosimeter.