Channel Wall Plasma Thermal Loads in Hall Thrusters with Magnetic Shielding

Abstract

Computer simulations using Hall2De identified the fundamental physical processes through which magnetic shielding can reduce channel wall erosion by orders of magnitude in Hall thrusters. Because magnetic shielding reduces significantly the energy and flux of the incident plasma a natural question is whether it has also a large effect on Hall thruster thermal design. In particular, if a Hall thruster is designed with magnetic shielding, will it be able to operate at significantly higher power densities than a conventional Hall thruster due to reduced thermal loads to the walls? If magnetically shielded Hall thrusters can operate at higher power densities, then high power Hall thrusters could be made smaller and lighter than present designs. In this paper we use Hall2De simulations of a laboratory thruster with and without magnetic shielding to predict the thermal loads from both ions and electrons including the self-consistently calculated wall sheaths. The formulations are similar to those previously applied in a hollow cathode thermal model. The numerical simulations show that, while magnetic shielding reduces high energy ion bombardment and power deposition in the acceleration zone of the discharge chamber, it has little effect on the total plasma thermal loads to thruster surfaces subject to plasma heating. Higher power densities were calculated on thruster surfaces downstream of the discharge chamber for the magnetic shielding configuration. Still, the reduction in peak plasma heating in the acceleration zone for the magnetic shielding configurations should reduce wall temperatures in this region that may lead to higher power density operation if the power deposition on the downstream surfaces for the magnetic shielded configuration can be mitigated.