Investigation of a Low-Frequency Rotating Spoke in Hall Thrusters

In recent studies~[1], we identified the presence of an E$\times $B rotating spoke in the cylindrical Hall thruster operating with a cusp-shaped magnetic field. The characteristics of the rotating spoke resemble previous observations for conventional~Hall thrusters of the annular geometry with predominantly radial magnetic field [2, 3]. It was suggested that the spoke is responsible for the enhancement of the electron current across the magnetic field. In this work, we use a high speed camera, electrostatic probes and segmented electrodes to measure the fraction of the cross-field current traversing the spoke towards the anode. \\[4pt] [1] J. Parker, et al., \textit{Appl. Phys. Lett} (Submitted 2010) \\[0pt] [2] G. S. Janes and R. S. Lowder, \textit{Phys. Fluids} (1966) \\[0pt] [3] A. I. Morozov, et al., \textit{Sov. Phys. Tech. Phys. }(1972)