The effects of breathing mode oscillations on ion energy distribution function in Hall thrusters: Time-resolved RPA measurements

Abstract

This paper presents a technique for reconstructing the temporal evolution of ion distribution functions (IDF) in a Hall thruster using ion currents measured with a retarding potential analyzer. The method involves averaging discharge oscillations with temporal realignment based on the maxima of the discharge current. This technique was applied to ion currents from the experimental ID-Hall 2 thruster, successfully reconstructing the time-dependent ion distribution function in quasi-periodic plasma oscillation regimes. The results indicate that deformations in the integrated ion distribution function can be attributed to the IDF's temporal evolution over a characteristic time equal to the breathing mode oscillation period. This finding suggests the possibility of uncoordinated displacement of ionization and acceleration zones within the discharge. In certain oscillation regimes, the oscillations in ion transit time also appear to have a minor effect on ion acceleration.