CHARACTERIZATION OF THE MAGNETIC NOZZLE REGION OF HIGH POWERED ELECTRIC PROPULSION THRUSTERS USING NUMERICAL SIMULATION, RF INTERFEROMETRY AND ELECTROSTATIC PROBES

Experimental results are presented from the plume of a 200 kW plasma gun emitting into an applied magnetic nozzle. Density profiles, electron temperature and ion velocity are measured in a region where the ratio of plasma kinetic pressure to magnetic pressure was Beta = 0.2 – 20. Numerical simulation is used to compare experiment results with theory predicting plasma detachment from B-fields. Significant plume deviation from B-fields was found for conditions of Beta > 1 in accordance with magnetic detachment theory. Nozzle efficiency estimates are provided based on simulated and measured conditions. In particular, an optimized magnetic nozzle condition is found theoretically improving nozzle efficiency by 10% over a nozzle-less condition. In addition, a new method is developed utilizing probes and RF interferometers in tandem. The density error was determined to be much lower than the error in probe measurements, and on the order of microwave interferometer uncertainty – as low as 10%.