Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Abstract

Erosion characteristics on the cover of the inner front pole in a 12.5 kW Hall thruster were measured over a wide range of operating conditions in tests of 6–14 h duration using an accelerated test method and a very sensitive, radioactive tracer-based erosion diagnostic. The operating points included the nominal 300–600 V conditions on a constant 20.8 A throttle curve and conditions at other currents spanning the throttling envelope and with varying magnetic field strength, facility pressure, and discharge voltage oscillation amplitude. Surprisingly, the results show that the highest wear rates occur at the lowest voltages and currents. The wear rates were insensitive to discharge voltage ripple but increased monotonically with magnetic field strength, particularly near the inner radius of the pole cover. The inner region was also sensitive to facility pressure, showing lower rates at a higher pressure level. Separate experiments in which the energy distributions of ions generated by the hollow cathode were measured suggest that the cathode plume may be a source of energetic ions responsible for some of the erosion trends, in addition to ions originating in the thruster plume.

Effects of the magnetic field intensity on pole erosion of low-power Hall thrusters

“…For example, a life test of * Author to whom any correspondence should be addressed. the 12.5 kW HERMeS thruster [2] showed that the maximum erosion rate of the inner pole cover reached 0.1 mm kh −1 at a 300 V discharge voltage and 0.04 mm kh −1 at a 600 V discharge voltage. The wear test results of a sub-kilowatt thruster showed that the overall average erosion rate of the magnetic pole was 0.01-0.084 mm kh −1 , however, the erosion rate at the maximum erosion position reached 0.496-0.849 mm kh −1 [3].…”