Investigation of Electron Extraction from a Microwave Discharge Neutralizer for a Miniature Ion Propulsion System

Abstract

To investigate electron extraction through the orifices of a microwave discharge neutralizer, three-dimensional particle simulations have been conducted. The numerical model is composed of a particle-in-cell simulation with a Monte Carlo collision algorithm for the kinetics of charged particles, a finite-difference time-domain method for the electromagnetic fields of 4.2-GHz microwaves, and a finite element analysis for the magnetostatic fields of permanent magnets. The distribution of the current density on the orifice plate obtained from the numerical model is in a reasonable agreement with the measurement result in an experiment. Moreover, the numerical results have indicated that the electrostatic field of the plasma has a dominant influence on the electron extraction although the electrostatic field produces the opposite force of extraction from the bulk plasma toward the orifice plate. The combination of the sheath potential barrier and the magnetostatic field yields the electron trajectories of extraction.