Hall Thruster Krypton Sputtering and Deposition for Vacuum Facility Materials

Electric propulsion (EP) ground tests need to account for multiple facility effects such as carbon sputtering, erosion, and deposition across the inner surfaces of both the thruster and vacuum chamber facilities. As part of a multi-university experimental investigation of the H9 Hall effect thruster as a part of JANUS (Joint Advanced Propulsion Institute), this paper reports on surface morphology of polycrystalline graphite with different grain sizes and stainless-steel 304 panels tested based on the total time integrated flux of incident ions produced by the thruster. Erosion and deposition observations are discussed with regard to their locations within the facility and expected ion flux from the plume. Scanning Electron Microscope (SEM) images provide useful qualitative surface morphology. Preliminary optical profilometry and laser confocal methods provide quantitative results but with high uncertainty due to the short test duration and surface anomalies; but inform improved approaches to future tests. Preliminary energy-dispersive X-ray spectroscopy (EDS) measurements reveal evidence of stainless-steel and aluminum sputtered material. These results support companion sputter/deposition modeling efforts and suggest that additional graphite shielding of facility surfaces and use of optimized volumetrically complex materials (VCMs) may prove beneficial.