Investigation into the Acceleration Region Dynamics of a Magnetically Shielded Hall Thruster Operating on Krypton

Hall thrusters are a promising candidate technology for scaling to the high powers and long lifetimes required for deep-space crewed and robotic exploration [1] . This has largely been enabled by the development of magnetic shielding, a technique that has greatly increased thruster lifetimes [2] , [3] . One of the remaining challenges in using Hall thrusters for deep space missions is the matter of propellant availability; xenon, the traditional propellant of choice, is greatly limited in the atmosphere [4] . A potential alternative to xenon is krypton, which is less expensive and more readily available. However, the efficiency of a magnetically shielded Hall thruster operating on krypton is 9-18% lower than that of the same thruster with xenon, a discrepancy primarily attributed to the lower mass utilization of krypton as shown in our previous work [5] . To further our understanding of the physical causes underlying this difference in efficiency, we need detailed measurements of the internal thruster channel. We accomplish this by employing laser-induced fluorescence, a non-invasive diagnostic technique, to measure ion velocity distribution functions along channel centerline of a shielded Hall thruster operating on krypton. We compare these results to previous measurements of the same thruster operating on xenon. These results yield insight into the mechanisms of krypton operation on a shielded Hall thruster and point to potential methods of improving its efficiency.