Investigation of Low Discharge Voltage Hall Thruster Operating Modes and Ionization Processes

A study of low discharge voltage Hall thruster operation revealed the existence of two operating regimes. Small variations in cathode flow fraction and magnetic field resulted in sharp changes in discharge current with constant thrust, corresponding to a visible change in the jet-mode plume structure. The phenomenon is characterized with a systematic map of thruster operation for discharge voltages ranging from 100 120 V, anode flow rates from 10 – 20 mg/s, and cathode flow rates from 7% to 25% of the anode flow. Far-field plume measurements show electron current to the anode is decreased during this transition. The ion energy distributions exhibit significant differences between the highcurrent and low-current operating modes. These differences are indicative of a significant increase in the fraction of low-energy multiply charged ions and a longer region of primary ion acceleration in the high-current mode. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 1 Research Scientist, Spacecraft Branch, Propulsion Directorate, AFRL/RZSS, [email protected]. 2 Professor, Department of Aerospace Engineering, Associate Dean, Horace H. Rackham School of Graduate Studies, Director, Plasmadynamics and Electric Propulsion Laboratory, [email protected].