In Situ Measurement of Hall Thruster Cathode Fluctuations

摘要

Measurements of Hall thruster cathode fluctuations are made in situ using an embedded pole cover probe. These fluctuations have been observed before but the connection between the measured modes remains elusive. Waves are measured with a high-speed camera, an embedded probe, and discharge current telemetry. These signals are compared in terms of frequencies and phases to establish properties of the observed modes. The results suggest that three modes are present: the breathing mode, a resonant global mode, and an azimuthal local cathode mode. The global and local modes are found to be distinct. The participation of the local mode in enhanced erosion is shown to be most likely minor. Further analysis suggests the frequency of the global mode is consistent with a 1:2:3 harmonic configuration.