Discharge Current Oscillation in Hall Thrusters

TLDR

The study investigates Hall thruster discharge current oscillations (10–100 kHz) to extend their stable operational range. Amplitude of oscillation was measured in anode‑layer and magnetic‑layer thrusters, a model linking frequency and stability was proposed, and the effect of divergent, parallel, and convergent acceleration channels was evaluated. Oscillation amplitude is sensitive to magnetic flux density and electron mobility, and a viscosity‑driven momentum transfer model shows that convergent channel configurations extend the stable operational range.

Abstract

The discharge current oscillation at a frequency range of 10-100 kHz in Hall thrusters was investigated with the objective of extending their stable operational range. The amplitude of oscillation was measured using two types of Hall thrusters-the anode layer type and the magnetic layer type. The oscillation amplitude was found to be sensitive to the applied magnetic flux density, and this result indicated that the oscillation was affected by electron mobility. An oscillation model was proposed based on the experimental results, and the predicted frequency and stable operational range were found to agree qualitatively agreed with the experimental results. This model shows that the momentum transfer corresponding to plasma fluctuation, that is, the viscosity effect, is crucial to achieving stability. Thus, the oscillation amplitude for various acceleration channel configurations-divergent, parallel, and convergent-was measured because the momentum transfer could be affected by the channel configuration. The stable operational range was successfully extended by the adoption of the convergent configuration in each type of Hall thruster, as shown by this model.