Simulation study of influence of exit magnetic separatrix angle on plume divergence control

Abstract

Cusped field thruster is a novel electrostatic thruster suitable for space exploration, but with high plume divergence angle. In this article, a 2D Particle-in-cell plus Monte Carlo (PIC-MCC) model is built to study the influence of exit magnetic separatrix angle on controlling plume divergence of cusped field thruster. The electric potential contour line distribution characteristics near exit magnetic separatrix with different angle are obtained and their formation mechanism is explained by magnetic mirror effect and electron pressure term. Simulation results show laying additional magnetic ring at the exit of channel can transfer exit magnetic separatrix towards inward of channel, which can decrease angle between electric potential contour line and central axis and increase ion axial speed. It is mainly due to change of magnetic field line direction and enhancement of magnetic mirror effect. However, simulation results show that ionization intensity in the channel decreases after adopting the plume control method. The plume divergence control method increases the channel length and causes the exit magnetic cusp inside the channel. Therefore the influence of exit magnetic separatrix angle on the characteristics of electron and ion energy deposition distribution on wall is further investigated.