Numerical simulation of magnetic field influence on plasma and electron extraction of electron cyclotron resonance neutralizer

Abstract

Electron cyclotron resonance (ECR) neutralizer is a key component of Electron Cyclotron Resonance Ion Thruster(ECRIT) with 10 cm diameter, which plays an important role in maintaining the spacecraft potential balance and neutralizing the ions in the plume region. Optimizing magnetic field distribution is an important ways to improve the properties of neutralizer, at the same time, the uniformity of the magnetic field and the position of the magnetic trap present the magnetic field characteristics and influence the plasma property, electron extraction procedure and beam current. In previous experimental researches, it was found that the beam current extraction performance of the two ECR neutralizers with different magnetic field uniformity and different magnetic trap locations is significantly different. However, it is difficult to reveal the physical phenomena and causes only through experiments, so numerical simulation is needed. Therefore PIC/MCC models for the ECR neutralizers with different uniformity of magnetic field and different position of magnetic trap are established. Under the given electron extraction potential, numerical simulations were accomplished to study, electron extraction procedure and analyze their influence on the performance of the neutralizer. The simulation results show that when the magnetic field uniformity is low and the magnetic trap is located upstream of extraction orifice, the electron migration from the magnetic trap to the outlet is restricted by the magnetic field and the electric field, then a higher potential energy is needed to extract the electron. otherwise when the magnetic field uniformity is high and the magnetic trap is located at the downstream of extraction orifice, electrons will migrate towards the magnet trap more likely. After the electron reaches the magnetic trap, under the action of the anode potential, the external potential is higher, and the external weak magnetic field almost loses its hold on the electrons, Therefore a large amount of electron beam can be extracted at low extraction potential. The research will lay an important foundation for the development of high-performance ECR neutralizer.