The facility effects of a Hall effect thruster's relative exhaust direction in ground tests

This research focuses on understanding how the relative pumping orientation and backpressure of a vacuum facility affects the measured performance and plasma plume parameters of a Hall-effect thruster (HET). A HET was operated in two opposite directions: plume ejection towards the vacuum pump and plume ejection away from the pump. The HET plume for each orientation was individually characterized at three vacuum facility operating pressures to study the effect of the facility pumping orientation and backpressure on the measured plume parameters and thruster performance. The ion current density, divergence angle, beam current, and ion energy distribution were measured using a Faraday probe and a retarding potential analyzer (RPA). The variation in the direction of the plume with respect to the pumping orientation leads to a clear difference in the measured performance of the HET when operating at an elevated backpressure. These are the first experiments that take the effect of the pumping orientation of a vacuum facility with respect to the thruster's exhaust direction into consideration. The results here will aid future research in selecting an adequate thruster exhaust direction when performing different Hall thruster ground tests such as plume diagnostics, lifetime tests, and erosion tests.