Design of Magnetic Circuit for Stationary Plasma Thruster

Abstract

SPT-100 electrostatic thruster is considered, and the effects of magnetic circuit is studied by introducing magnetic screen. The magnetic flux density in the discharge channel is generated with the help of one inner coil and four outer coils. The radial magnetic field has to be maximum near the exit plane of the thruster to trap the electrons in acceleration region which are emitted from an external hollow cathode. These electrons help in increasing the ionization rate of the propellant gas. This is obtained by placing magnetic poles near exit plane. It helps to traps the electrons emitted from the external hollow cathode. The magnetic circuit should be designed such that the magnetic flux density is near to zero at the anode plane to reduce interaction of electrons with channel walls. To arrive at such better design, magnetic screens are used. Computational simulations are performed to quantify the magnetic flux density distribution along the channel using COMSOL Multiphysics software. The simulation results show that the obtained radial magnetic flux density is maximum near the exit plane, and the magnetic screens help in reducing the magnetic field at the anode region while maintaining the maximum magnetic field at the exit plane.