Cross-Field Electron Transport Induced By A Rotating Spoke In A Cylindrical Hall Thruster
Authors: C.L. Ellison, Y. Raitses and N.J. Fisch
Abstract:
Rotating spoke phenomena has been observed in a variety of Hall thruster and other
E x B devices. It has been suggested that the spoke may be associated with the
enhancement of the electron cross-field transport. In this paper, the current conducted across the magnetic field via a rotating spoke has been directly measured for
the first time in the E x B of a cylindrical Hall thruster. The spoke current was
measured using a segmented anode. Synchronized measurements with a high speed
camera and a four-segment anode allow observation of the current as a function of
azimuthal position. Upwards of 50% of the total current is conducted through the
spoke, which occupies a quarter of the Hall thruster channel. To determine the transport mechanism, emissive and Langmuir probes were installed to measure potential
and density fluctuations (respectively). An azimuthal electric field and density
fluctions are observed to oscillate in-phase with the rotating spoke. A contributing
transport mechanism is proposed to be an axial E x B electron drift towards the
anode caused by the perturbed azimuthal electric field.
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Submitted to: Physics of Plasmas (August 2011)
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