Impact of thruster body electrical configuration on Hall effect discharge impedance characteristics

This paper investigates how grounded, floating, and cathode-tied thruster body electrical configurations affect current pathways in a vacuum test facility and the Hall effect thruster discharge impedance from 100 Hz to 300 kHz. A current pathways model is extended to include the thruster body pathway and is used to interpret witness-plate ion and electron current measurements, discharge telemetry, and small signal impedance measurements. The witness-plate measurements reveal configuration-dependent changes in far-field electron collection. The cathode-tied configuration produces the highest electron saturation currents at nearly all measurement locations, whereas the grounded configuration produces the lowest values at nearly all background plasma locations. The impedance measurements similarly reveal configuration-dependent resistance and reactance. Near the dominant breathing mode frequency, the grounded configuration exhibits an impedance magnitude about 30% higher than those of the other configurations and a positive to negative phase transition near the first impedance peak. The grounded configuration also produces discharge-current peak-to-peak oscillations approximately 16% larger than those measured in the other configurations. Its reactive response is consistent with a possible contribution from plasma sheath capacitance, although this contribution cannot be independently separated from other reactive effects associated with the implemented electrical configuration. Together, these results demonstrate that the conductive thruster body functions as an electrical boundary condition that influences the effective discharge load impedance and the distribution of far-field electron current pathways.