DocumentCode :
1766251
Title :
Azimuthal Spoke Propagation in Hall Effect Thrusters
Author :
Sekerak, Michael J. ; Longmier, Benjamin W. ; Gallimore, Alec D. ; Brown, Daniel L. ; Hofer, Richard R. ; Polk, James E.
Author_Institution :
Dept. of Aerosp. EngineeringPlasmadynamics, Univ. of Michigan, Ann Arbor, MI, USA
Volume :
43
Issue :
1
fYear :
2015
fDate :
Jan. 2015
Firstpage :
72
Lastpage :
85
Abstract :
Spokes are azimuthally propagating perturbations in the plasma discharge of Hall effect thrusters (HETs) that travel in the E x B direction. The mechanisms for spoke formation are unknown, but their presence has been associated with improved thruster performance in some thrusters motivating a detailed investigation. The propagation of azimuthal spokes are investigated in a 6 kW HET by using high-speed imaging and azimuthally spaced probes. The spoke velocity is determined from high-speed image analysis using three methods with similar results. The spoke velocity for three discharge voltages (300, 400, and 450 V) and three anode mass flow rates (14.7, 19.5, and 25.2 mg/s) are between 1500 and 2200 m/s across a range of magnetic field settings. The spoke velocity is inversely dependent on magnetic field strength for lower B-fields and asymptotes at higher B-fields. Spoke velocities calculated from the probes are consistently higher by 30% or more. An empirically approximated dispersion relation of ωα = vchαkθα - ωchα where α ≥ 1 yields a characteristic velocity that matches the ion acoustic speed for N5 eV electrons which exist in the near-anode and near-field plume regions of the discharge.
Keywords :
discharges (electric); ion engines; plasma devices; plasma ion acoustic waves; plasma magnetohydrodynamics; plasma probes; Hall effect thrusters; anode mass flow rates; azimuthally propagating perturbation; azimuthally spaced probes; dispersion relation; high-speed image analysis; ion acoustic speed; magnetic field strength; plasma discharge; plasma probes; power 6 kW; spoke velocity; velocity 1500 m/s to 2200 m/s; voltage 300 V; voltage 400 V; voltage 500 V; Discharges (electric); Magnetic resonance imaging; Magnetic separation; Magnetoacoustic effects; Oscillators; Plasmas; Probes; Aerospace industry; hall effect devices; plasma diagnostics; plasma measurements; plasma waves; satellites; space technology; space technology.;
fLanguage :
English
Journal_Title :
Plasma Science, IEEE Transactions on
Publisher :
ieee
ISSN :
0093-3813
Type :
jour
DOI :
10.1109/TPS.2014.2355223
Filename :
6919317
Link To Document :
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