Hall thruster discharge chamber plasma characterization using a high-speed axial reciprocating electrostatic probe
Electron temperature, number density, plasma potential and floating potential were measured in the interior and very-near-field region of the P5 Hall thruster using the newly developed High-speed Axial Reciprocating Probe (HARP) positioning system. The HARP system was used to insert an electrostatic triple probe axially into the discharge chamber from 152 mm downstream of the exit plane to within 5 mm of the anode face, maintaining residence times under 100 ms. Probe data, discharge current and cathode potential were recorded continuously during probe movement; the latter two quantities verified the HARP system’s limited perturbation to thruster operation. A second, slower, linear table was used to vary the radial location of the probe between axial sweeps resulting in a 2-D mapping of the chamber. Two thruster operating conditions were considered: 300 V, 5.3 A and 100 V, 5.3 A. At 300 V, a very complex plasma structure was observed. Regions of high electron temperature and plasma potential were observed near the anode and along the outer wall of the channel. Number density peaked on centerline near the region of high temperature and again downstream of the exit plane. A large accelerating potential was shown to exist outside the discharge chamber, agreeing with LIF ion velocity measurements at the exit plane. At 100 V, the coherent structure is largely absent which is expected based on the thruster’s poor performance at this condition. © 1999 by the American Institute of Aeronautics and Astronautics, Inc.
