Transport-Property Measurements in the Plume of an SPT-100 Hall Thruster

Abstract

To understand the interaction between the SPT-100 thruster and the spacecraft, accurate knowledge of exhaust plume properties must be obtained. This investigation utilized a suite of interrelated diagnostic probes in an effort to provide detailed knowledge of the exhaust plume on a molecular kinetic level. Probes used for the investigation included a retarding potential analyzer, a planar Faraday probe, an emissive probe, both totaland radiant-heat- ux probes, as well as a newly developed neutral particle  ux probe. Combining the knowledge gained from these probes it was possible to quantify the transport of mass, energy, and charge within the plume at 0.5and 1.0-m radius from the thruster exit. Among the phenomena uncovered were a high-energy ionic annulus surrounding a narrow low-energy core within the plume at 0.5-m radius from the thruster exit. This core structure was Ž lled in at 1.0-m radius. Additionally, a population of energetic charge-exchange neutrals was found within 25 deg of the thruster centerline along with the corresponding low-energy charge-exchange ions attributed to plume/background gas interactions.