An Approximation for the Electron Sheath in SGEMP

A new technique is introduced for calculating the effect of strongly limited electron emission of the SGEMP response of a body in space. The approach is a generalization of the non-screening approximation of Karzas and Latter; it consists of a simple, electromagnetically self-consistent algorithm for treating electrons which limit near the body. As a result only those trajectories of particles which have large spatial excursions need to be calculated in detail. Results for the one-dimensional planar problem are presented for various electron current and velocity distributions and compared with the results of solving the problem following all particle trajectories. In particular, for monoenergetic square pulse emission, the so-called "diode oscillations" are obtained and an analytical estimate of the effect is given using the nonscreening approximation. Results for a two-dimensional cylindrical object are obtained and compared with pure particle-pushing techniques at different fluence levels and various emission patterns. The comparison is very favorable, with important savings in time and storage in the computer calculations. The present approach is easily generalizable to 3-D, where it should prove to be a valuable tool to attack, in a concise and accurate fashion, the strongly limited SGEMP response of such an object in space.