Model for space charge evolution and dose in irradiated insulators at high electric fields

A method for calculating dose, charge deposition, current, and electric field profiles across a dielectric slab irradiated by 1-3 MeV electron beams has been developed. The model consists of following the electric field build-up with time. A sequence of Monte Carlo calculations for relativistic electrons moving in an electric field determines the motion of the high-energy electrons. This is coupled with electric field solutions using a 1-D electrostatic field code. As time proceeds, the profile of high-energy electron current changes as well as the dose deposition which affects the magnitude of the conduction currents. Several mechanisms for conduction in the dielectric are taken into account. The model predictions are compared with Kerr-effect electric field data on irradiated polymethylmethacrylate (PMMA) obtained by M. Hikita et al. (1988)