Ultrahigh Speed Images of Hall Thruster Azimuthal Instabilities

Visible emission of the azimuthal plasma instabilities were observed within the plume of a low-power Hall thruster utilizing ultrahigh speed imaging. The captured images provide time-dependent and spatial information on the azimuthal instability in the axial-radial plane of the thruster, which have not been well characterized. These images are then compared with observations made based on their probe measurements of azimuthal instabilities termed spoke instabilities. Data from the images show that the spoke instabilities are more complex than originally described and have additional features not detectable with probe measurements in a single plane.