Plasma oscillations below 100 kHz in a high-power, magnetically shielded Hall-effect thruster are characterized experimentally. A time-resolved laser-induced fluorescence diagnostic was used to measure the evolution of the axial ion velocity distribution along the discharge channel centerline. A method was developed to correct for artificial broadening of the distribution due to finite spatial resolution, enabling accurate ion temperature measurements in the acceleration region. Time-dependent ion heating behavior is revealed, which varies with axial location. Electrostatic, collisionless particle-pushing calculations were employed to simulate the effects of a shifting acceleration front on ion motion. It is found that ions exchange energy with these oscillations, which accounts for a portion of the ion velocity fluctuations observed in the thruster plume. Phasing relationships between ion dynamics and discharge current oscillations are discussed in the context of prior Hall thruster experiments.
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