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2 Journal of Technical Physics

2 2008

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Bismuth Hall thruster II: Simulated diagnostics

Scharfe D. B., Capelli M. A.

Journal of Technical Physics

2008

Vol. 49, no 3-4

349-361

A laboratory-model bismuth-fueled Hall thruster has been designed, and the geometry of that design has been incorporated into a 2-D radial-axial hybrid Hall thruster simulation. Velocity distribution data from the plume of that simulation, incorporated with calculations based on the known spectroscopy of the bismuth ion, have been used to simulate optical diagnostic measurements of the exhaust velocity of the thruster. Simulated Laser Induced Fluorescence ana emission spectroscopy data has been produced, assuming that the 14681.971 cm-1 transition of ionized bismuth is analyzed. The simulated Laser Induced Fluorescence assumes a narrow line-width, scanning laser probes the plasma either axially or radially, and it is suggested that the fluorescence be collected about the 15146.544 cm-1 transition; emission results have been simulated with varying instrument resolutions and with collection angles at 0° and 60° off the axial axis.

Bismuth Hall thruster I: Simulation-suggested design and performance

Scharfe D. B., Scharfe M. K., Capelli M. A., Fernandez E.

Journal of Technical Physics

2008

Vol. 49, no 3-4

329-348

A two-dimensional radial-axial hybrid simulation of the xenon-fueled Stanford Hall Thruster has been adapted to model a bismuth-fed thruster with varying channel geometry. The simulation treats the electrons as a quasi-one-dimensional fluid and the neutrals and ions as discrete superparticles advanced using a particle-in-cell (PIC) approach. Since experimental data of the electron cross-field mobility does not exist for the bismuth-fueled thruster, a model for electron transport based on shear suppression of plasma turbulence is used to compute a mobility from simulated plasma properties. While the bismuth propellant showed poor performance with an 8 cm channel length, results improved significantly as the simulated channel was shortened to 3.3 and 2.4 cm. The simulation of bismuth propellant at the shortest channel length provided significantly improved ionization fraction, thrust, efficiency, and thrust-to-power compared to xenon propellant on either the 8 cm or 2.4 cm channel, as can be expected due to the higher atomic mass and lower ionization potential of bismuth. With results indicating that optimal performance of the bismuth thruster occurs with a sub-3 cm channel length, such a design is suggested for a developing laboratory-model bismuth thruster.