Far-Field Species Distribution Measurements on the BHT-600 Hall Thruster Cluster

Abstract

Measurements via the Top Hat Electric Propulsion Plume Analyzer (TOPAZ) on theBusek BHT-600 Hall thruster cluster are presented. TOPAZ incorporates a 'top hat' 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. I. Nomenclature= deflection plate gap radius R 2 = grounded plate gap radius R 3 = top hat radius R C = gap centerline radius R G = guiding plate radius R P = particle radius of motion S = aperture radius= time-of-flight distance m = particle mass q = charge of particle t TOF = particle time-of-flight v = velocity ∆R = gap distance ∆x = distance between exit of gap and particle detector α = elevation angle β = azimuthal angle of incoming particles 1 Former Graduate Student, Department of Aerospace Engineering, allen.victor@gmail.com.