Time-synchronized laser-induced fluorescence in the near-field of a 600 Watt Hall thruster

Abstract

We report on the results of an experimental campaign to measure time-varying velocity distributions in the near-field of a low power Hall thruster. We employ a sample-hold technique, enhanced by parallelizing the measurement hardware into several signal processing channels that vastly increases the data acquisition rate. The measurements are applied to study flow field dynamics in a commercial BHT-600 Hall thruster undergoing unforced breathing mode oscillations in the 44-49 kHz range. A very detailed experimental picture of the nearfield emerges from these studies. The results indicate that velocity fluctuations lessen further downstream of the exit plane. Along the thruster axis, where there is a general appearance of a central jet, there is evidence of a low velocity ion population in between the periodic bursts of high velocity ions, indicative of local ionization of neutrals outside of the thruster. One possible source of this residual ionization may be background chamber gas, which is not unexpected with the limited pumping capacity of ground test facilities.

On a force balance and role of cathode plasma in Hall effect thrusters

“…For example, in [85] using the LIF method, it was found that a multi-peaked iVDF is present at the outer radius of the plume even at a great distance from the thruster. In [86][87][88], LIF measurements of the iVDF were carried out near the channel, depending on the time. It was found that the a peak of slow ions was periodically formed at a distance of about 15 mm from the channel's exit at the lower half-wave of breathing oscillations.…”

Accuracy of using metastable state measurements in laser-induced fluorescence diagnostics of xenon ion velocity in Hall thrusters

“…Measurements of ion dynamics are also useful for improving understanding of the physics involved in Hall thrusters and observed phenomena such as anomalous electron transport [4][5][6][7][8][9][10]. Since LIF is a well established diagnostic used throughout the electric propulsion community, it is important to be aware of the assumptions involved and to investigate those assumptions when possible [11].…”