X-ray induced conductivity in insulating materials

Abstract

A co-ordinated explanation of the conductivity induced by ionizing radiation in solid insulating materials (conductivity ~ 10 -20 Q -1 cm -1 ), including amber, mica and a number of plastics, is put forward for the first time. A model based on conduction by free electrons and including the presence of electron traps is proposed, and the theoretical predictions based thereon are shown to be in good agreement with the experimental results. The dependence of induced conductivity and of the subsequent decay upon temperature and dose rate have been investigated. Physical parameters are given for each material: recombination crosssection, number of traps and their distribution in energy, mean distance diffused by free electrons and probability factors of release from traps. The results suggest that when crystalline regions are present in a material (e.g. polyethylene), the boundaries of these regions provide trapping sites in addition to traps of unspecified nature which are present in completely amorphous materials.