Plasma Plume Characterization of a 100 kW Nested Hall Thruster

Abstract

The plasma plume properties of a three-channel 100-kW-class nested Hall thruster were measured on xenon propellant for total powers up to 80 kW. The thruster was throttled through all seven available channel combinations for conditions spanning 300 to 500 V discharge voltage and three discharge current densities. A plasma diagnostics array, which included a Wien filter spectrometer, a retarding potential analyzer, and a planar Langmuir probe, was placed in the far-field plume of the thruster and used to measure the beam ion charge state, the ion energy distribution function, and the local plasma potential. These data were used to calculate thruster phenomenological efficiencies. These efficiencies are compared across the discharge voltage and channel combination, and they are compared to similar results from the NASA-300M single-channel high-power Hall thruster. An estimate of cross-channel ingestion, which is a phenomenon in the nested configuration that may improve thruster efficiency and that will be present in space, is calculated, and the results for mass utilization efficiency are corrected for this effect. These plasma diagnostic results are discussed in the context of the state of the art, as well as in that of the viability and potential benefits of the nested channel thruster configuration.