Study of the Discharge Chamber Magnetic Field Configuration Effects on the Electron Cyclotron Resonance (ECR) Microwave Ion Thruster

摘要

Microwave ion thrusters that employ the gyromotion of the electrons around an external static magnetic field lines to obtain discharge are among the most selected devices for deep space missions that require longer life time. The phenomenon of electron cyclotron resonance (ECR) is utilized to a high degree to energize the electrons in magnetic tubes created by the lines of force and obtain discharge through impact ionization. A discussion for the trade-offs between microwave systems to other electric propulsion systems is presented along with numerical simulations on some designs from literature. COMSOL Multiphysics, a finite element software, is used to conduct magnetic field simulation, electromagnetic simulation and plasma simulation. Results show that the increase in number of magnets and orienting them to form cusps affect the density and temperature distribution by increasing the magnetic tubes in which the electrons are trapped and energized. The R-mode and X-mode resonance regions are plotted, and for 20mN-class ion thruster it is verified that X-mode resonance is the dominant energy transfer mechanism.