Operation of a segmented Hall thruster with low-sputtering carbon-velvet electrodes

Abstract

Carbon fiber velvet material provides exceptional sputtering resistance properties exceeding those for graphite and carbon composite materials. A 2kW Hall thruster with segmented electrodes made of this material was operated in the discharge voltage range of 200–700V. The arcing between the floating velvet electrodes and the plasma was visually observed, especially, during the initial conditioning time, which lasted for about 1h. The comparison of voltage versus current and plume characteristics of the Hall thruster with and without segmented electrodes indicates that the magnetic insulation of the segmented thruster improves with the discharge voltage at a fixed magnetic field. The observations reported here also extend the regimes wherein the segmented Hall thruster can have a narrower plume than that of the conventional nonsegmented thruster.

Enhanced performance of cylindrical Hall thrusters

“…The plasma plume angle is usually defined as the angle that contains not less than 90% of the total ion current. 2,15 For the CHTs, the half plume angle can be as large as 60-80°, 8 compared to 45-50° for the state-of-the art annular…”

“…2 For the annular Hall thrusters, the beam divergence is due to the combined effect of radial pressure gradients, magnetic field curvature, and the nonuniform distribution of the ion production. 13,14 Controlling the placement and length of the ion acceleration region using segmented electrodes 15 or by optimizing the magnetic field topology 2,13 were shown to narrow the plasma plume in the annular thrusters.…”

“…A commercial hollow cathode was used as a cathode-neutralizer. 8,11,12 During the plume measurements, the background pressure in a 28 m 3 vacuum vessel equipped with cryopumps 15 did not exceed 3 microtorr. The thrust-stand, thrust measurement procedures, and experimental uncertainties are described in detail elsewhere.…”

Cathode Effects in Cylindrical Hall Thrusters

“…The half plume angle of a CHT can be as high as 60-80 • [3], compared to 45-50 • for the best annular Hall thrusters [8], where the plume angle is defined as the angle that contains at least 90% of the total ion current [8][9][10]. The resulting anode efficiency is typically 15-25% in the 100-200 W power range [11].…”

Cathode effects in cylindrical Hall thrusters

“…• for the best annular Hall thrusters [8], where the plume angle is defined as the angle that contains at least 90% of the total ion current [8][9][10]. The resulting anode efficiency is typically 15-25% in the 100-200 W power range [11].…”