Radiation Induced Currents and Conductivity in Dielectrics

Methods for measuring induced conductivity due to high energy (> 10 keV) irradiation in dielectrics are discussed. Transition zone dosimetry and secondary electron transport data are incorporated in a new methodology which includes space charge effects and time dependent replacement currents. In addition, a radically different method for the measurement of radiation induced conductivity which takes advantage of space charge fields is proposed which should be advantageous for in-situ measurements. Results of experiments using both methods on several organic polymers irradiated by 60Co photons are presented. Time dependent replacement current is measured and compared to theoretical prediction. Experimentally measured replacement current is in agreement with calculations based on published theoretical photocompton current data for field free conditions. An equation for estimating the maximum space charge field generated by high energy photons or electrons is proposed.