Time-Resolved Ion Energy Measurements in the SPT-50 Hall Effect Thruster

An investigation into time-resolved ion energy measurements of the 300-W SPT-50 Hall effect thruster (HET) utilizing a high-speed retarding potential analyzer (HSRPA) is presented. Ion energy as a function of HET operating condition and downstream position was measured. High-speed measurements were performed with a standard retarding potential analyzer (RPA) in conjunction with high-speed, low-noise circuitry, allowing fast collector current measurements at discrete retarding biases. Time-averaged and time-resolved ion energy measurements were observed to establish a relationship between ion energy, discharge conditions, and downstream position. Time-series data were reconstructed using data fusion techniques allowing time-resolved ion energy distribution functions (IEDFs) to be acquired. Time-resolved ion energy measurements varied in mean, peak-to-peak, and temporal characteristics as the operating conditions and position were varied.