Analytical Extraction of Plasma Properties Using a Hall Thruster Efficiency Architecture

An investigation of the conversion from anode electrical energy to jet kinetic energy in a laboratory model Hall thruster yielded an experimentally determined thrust efficiency that was analytically decomposed into the product of propellant, voltage, and current utilization efficiency. This method accounts for loss of propellant utilization from plume divergence, unionized propellant, and multiply charged ions. Current and voltage utilization losses include recycled electrons used for ionization processes and the fractional loss of acceleration voltage within the discharge chamber. The architecture of the efficiency analysis is such that energy efficiency becomes naturally expressed as a product of voltage and current utilization efficiencies, and is rigorously separated from propellant utilization efficiency. A systematic investigation of thruster performance and the far-field plume provided insight into the loss mechanisms and plasma properties from 100 to 400 V discharge for constant mass flow rate (20 mg/s) and constant power operation (6 kW). Experimental parameter groups were calculated based on the measured thrust and telemetry data. When interpreted with measured ion beam current and most probable ion voltage, the efficiency analysis enabled several plasma parameters to be deciphered, including: average ion charge, ionization mass fraction, and momentum beam divergence half-angle. The following study creates an analytical procedure for extracting plasma parameters based on macroscopic performance and plume measurements, and enables the interpretation of limits for consistent sets of allowable discharge properties. DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Җ Research Scientist, ERC Inc.; Ph.D. candidate, University of Michigan: [email protected] Σ Research Scientist, Spacecraft Propulsion Branch: [email protected] $ Group Lead, Spacecraft Propulsion Branch: [email protected] α Professor and Laboratory Director, Department of Aerospace Engineering; Associate Dean, Horace H. Rackham School of Graduate Studies: [email protected]