The saturation curve for ionization measurements in pulsed radiation beams.

Abstract

In a previous paper (Boag, 1950) the saturation curve for an ionization chamber exposed to pulsed radiation was investigated mathematically and some preliminary measurements were presented, but experimental difficulties prevented any great reliance being placed on these measurements, and there was at that time no possibility of repeating them. It has recently been possible to make some further measurements, using as a source of pulsed radiation the 8 MeV linear accelerator, which is under construction for the Medical Research Council at the Trafford Park works of the Metropolitan-Vickers Electrical Company. The ionization chamber used for these measurements is illustrated in Fig. 1. The chamber was constructed from perspex, the electrode surfaces being coated with colloidal graphite. The spacing of the electrodes could be varied by means of interchangeable rings which were made to give air gaps of 0·48 mm., 0·99 mm., 1·47 mm., and 1·98 mm. respectively. A guard ring was provided to ensure that the electri...