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Near-field ion energy and species measurements of a 5 kw laboratory hall thruster

The Plasmadynamics and Electric Propulsion Laboratory (PEPL) has used its Molecular Beam Mass Spectrometer (MBMS) to determine the ion energy distribution of the P5 5 kW laboratory Hall thruster. A skimmer was used to obtain a sample of the plasma in the near-field region, 10 cm downstream of the thruster exit plane. The thruster was operated at several discharge conditions and was rotated with respect to the sampling skimmer in order to determine ion energy profiles at various plume angles. These measurements were compared to far-field ion energy measurements taken 75 cm from the discharge plane in order to examine the evolution of the ion energy profile and the effects of testing environment on the results. Both ion energy measurements and time-of-flight mass spectroscopy revealed evidence of singly, doubly, triply, and quadruply charged xenon ions within the plume. Ion energy distributions were used to determine that the thruster’s magnetic field was oriented such that the plume has an overall inward focus. It was seen that sampling the plasma closer to the thruster results in distributions that have undergone fewer changes as a result of collisions with other ions in the plume and with background neutrals within the test facility. Concerns regarding these facility effects have led to the development of a new Miniaturized Ion Energy Analyzer (MIEA) for future experimental work.