Far-field species distribution measurements on the BHT-600 hall thruster cluster
Measurements via the Top Hat Electric Propulsion Plume Analyzer (TOPAZ) on the Busek BHT-600 Hall thruster cluster are presented. TOPAZ incorporates a 'top ha design with an analyzer constant of 100 resulting in a wide energy-range capability and high angular and energy resolutions. A time-of-flight analyzer is also incorporated for mass-tocharge (and hence charge-state) discrimination from within the plume. Energy profiles measured from different regions of the cluster revealed lower-energy (i.e., energies significantly below the discharge voltage) ions emanating from positions closer to the cathode, while higher-energy (i.e., energies near or higher than the discharge voltage) ions were measured along the discharge channel centerlines. Low-energy ions were also measured from behind the cathodes only during cluster operation indicating a possible cross-pollination of the cathode plume with the opposite thruster. Multiply-charged xenon ions (i.e., Xe 3+ and Xe 4+) were measured for 0° and 10° plume angles while the 20° plume angle revealed mostly singly- and doubly-charged xenon. Calculations of the axial and radial velocity distributions for the first three charge-states downstream of the cluster centerline revealed a symmetric triple-peak structure in the radial velocity distributions and a doublepeak profile in the axial velocity distribution of the first charge-state of xenon.
