Analysis of Time-Dependent Radiation-Induced Conductivity in Dielectrics and Effect on Cable SGEMP

Analytic and numerical solutions are presented for a simple time-dependent solid-state band model of radiation-induced conductivity in polyethelene and Teflon. The analytic solution is found to provide insight to physical processes dominant in various intervals of time throughout the radiation pulse. The numerical solution provides a representation for the dose-dependent proportionality factor F(γ), proposed by van Lint et al, used to calculate prompt conductivity from σp = F(γ)γ. At high doses, F(γ) is an order of magnitude smaller than at low doses. This decrease of F(γ) is due to bimolecular recombination, an effect apparently not previously reported experimentally. The reduction in F(γ) at high doses is shown to enhance the short circuit current for a cable SGEMP model of residual gaps by a factor of three. In addition, the dose-dependent behavior of F(γ) can significantly alter the shape and time of occurrence of the peak of the waveform of this short circuit current compared to corresponding results for a dose-independent factor.