Time-Synchronized Continuous Wave Laser Induced Fluorescence Velocity Measurements of a 600 Watt Hall Thruster

A time-synchronized continuous wave laser induced fluorescence diagnostic technique based on a sample hold scheme is applied to xenon ion velocimetry of a BHT-600 Hall thruster plume. This method is capable of correlating measured fluorescence excitation lineshapes with current fluctuations in a plasma discharge and is tolerant of natural drifting in the current oscillation frequency. This paper presents time-synchronized axial ion velocity measurements in the channel and near-field plume region of a 600 W Hall thruster operating on xenon. Results show significant fluctuations in LIF signal intensity (correlated with the density of the probed excited metastable state) in time during the discharge current cycle, with the peak intensity occurring at the discharge current maximum. Measured ion velocities also fluctuate in time with the current oscillation, reaching their peak after the discharge current maximum. This work provides detailed insight into the complex, time-dependent ionization and ion acceleration mechanisms in the channel of a Hall thruster that would be unattainable with a time-averaged measurement.