Mass Spectral Measurements in the Plume of an SPT-100 Hall Thruster

Knowledgeoftheion speciesemittedbytheSPT-100Hallthrusterprovidesconsiderableinsighttobasicthruster performance. To gain detailed information concerning the composition of the plume plasma, a unique molecular beam mass spectrometer was constructed to interrogate the exhaust plume. An investigation using this technique yielded boththeionizationfraction ofthexenonpropellantandaqualitativeanalysisoftheminorityplasma species attributed to ground-test facility interactions. The plasma was found to consist of 89% Xe + , 11% Xe 2+ , and 0.2% Xe 3+ . The existence of parasitic facility gasses including nitrogen, oxygen, and water vapor was documented, as well as trace carbon ions caused by sputtering of graphite surfaces in proximity of the thruster.