Determination of In-Orbit Plume Characteristics from Laboratory Measurements

Abstract

This paper describes a method to determine the “in-orbit” plume of a Hall Effect Thruster from laboratory measurements. Plume measurements were taken with a Faraday probe and a Retarding Potential Analyzer at different background pressures to correlate changes in the current density with changes in the ion voltage distribution. Results showed that the current density increases linearly with background pressure for any given angle. This linear relationship was used to extrapolate the measurements to zero background pressure, the “in-orbit” condition. Measurements from both the Faraday probe and the Retarding Potential Analyzer were checked against each other to ensure consistency. The effect of discharge voltage on plume divergence was also investigated. The thruster was operated at discharge voltages ranging from 300-1000V. Measurements from both probes showed that plume divergence decreases as discharge voltage increases.