A Self-Consistent Two-Dimensional EMP Code for Space-Charge Limiting and Secondary Emission

This article discusses the relative merits of particle pushing versus direct differencing of Boltzmann's equation for solving space-charge-limited problems in the presence of secondary emission. Direct differencing seems preferable in two-dimensional geometries and hardvacuum environments. A set of numerical solutions are presented for the problem of a long gap 3cm wide illuminated by a 2 keV blackbody pulse carrying 1.45×10-4 cal/cm2. The gap is normally illuminated, and is presumed to be bare aluminum on one side, and mylar-coated aluminum on the other. The different emissivities of these two surfaces cause a voltage to develop across the gap. Omission of secondary-electron effects leads to predicted voltages which are a factor of two higher than those obtained with secondary-electron effects inclusion.