Experimental Determination of Collection Efficiency of Ionization Chamber in Field of Pulsed X-Rays

Abstract

The collection efficiency f-value of a parallel-plate ionization chamber exposed to a pulsed X-ray field of high exposure rate has been discussed. The dependence of the f-value upon various parameters was clarified by numerical calculations of the rate equations for positive and negative ions. The saturation curve was also obtained with the normalized variables.
A method was proposed for determining the f-value in an unknown pulsed X-ray field. It was found that the true f-value could be evaluated by fitting a normalized saturation curve to several ionic charges at different applied voltages. Experiments were carried out in a pulsed X-ray field generated by an electron linear accelerator, and the effectiveness of the method was confirmed.