Plume Profiles of a Planar Crossed-Field Thruster with Hall Current Injection

Abstract

Stable operation of a Hall thruster that emits and collects the Hall current across a planar discharge channel is described. Hall current was emitted by hollow cathode electron sources and collected by electrodes on the opposing wall of the thruster. During this initial test, the planar Hall thruster was operated at discharge voltages between 100― 150 V. Internal channel wall probes, along with a downstream Faraday probe and retarding potential analyzer, measured changes in thruster plasma as the discharge voltage and magnetic field were adjusted. Results show that most of the plume ions were created in the acceleration zone and gain only 60―70% of the discharge voltage. Furthermore, the axial plume ion energy decreased with increasing magnetic field. Specifically, when the electromagnet was increased from 1.5 to 3.5 A, the ion energy decreased 25%. The plume current density profile showed a peak at 15―20 deg off-centerline, and this angle increased with increasing magnetic field. Specifically, when the electromagnet was increased from 1.5 to 3.5 A, the peak location shifted 4 deg farther from the centerline. Analysis of these results suggests that a buildup of Hall current electrons on one side of the discharge channel leads to a nonuniform plasma density. Further, magnetohydrodynamic effects on the expelled ion beam leads to cross-field ion velocity, resulting in the off-centerline peak in the current density profile.