Effect of magnetic field strength on the performance characterization of a low-power wall-less Hall thruster

Abstract

The wall-less Hall thruster is expected to overcome the issue of wall erosion in miniaturized Hall thrusters. A unique structure of negative gradient magnetic field is used to constrain the plasma behavior. In this paper, permanent magnet rings with different thicknesses were used to adjust the magnetic field strength, and its effect on discharge characteristics and thrust performance was experimentally investigated. The experiment results show that increasing the magnetic field strength can reduce the current oscillation and increase the maximum operating voltage. Within a limited range, increasing the magnetic field strength can significantly improve thrust performance. However, excessive magnetic field strength leads to a decrease in anode efficiency. The optimal magnetic field strength appears at 121 mT, with a thrust of 5.5 mN, a specific impulse of 935 s, a thrust power ratio of 51 mN/kW, and an anode efficiency of 23.1 %. Based on the analysis of different efficiency parameters and plume images, under excessively high magnetic field strength, the shortening of the ionization region may lead to intensified leakage of neutral atoms, which may be the primary reason for the reduction in propellant utilization and anode efficiency.