离子推进器中离子束中和及推进过程的全粒子数值模拟

Full Particle Numerical Simulations of Ion Beam Neutralization and Propagation Process for Ion Thruster

为优化离子推进器结构,对离子推进器中和过程中的离子–电子耦合及电中性等离子体形成过程的物理机制进行了研究。采用2维轴对称全粒子质点网格法对离子束中和过程和近场羽流进行了数值模拟。结果表明,在靠近推进器出口处的离子束中会形成1个较高的正电势,且该正电势会随着时间逐渐增大。推进器出口处的高电势与周围环境之间形成的势阱能够限制电子的逃逸并加速离子,最终使得2者的速度趋于一致,完成离子–电子的耦合过程,即离子束的中和过程。在以上过程中,沿着等离子体束推进方向的电子和离子的动能增加,电子的热能降低。

In order to optimize ion thrusters, we investigated the ion-electron coupling in ion beam neutralization process and the physical mechanism of electrically neutral plasma＇s formation. A two-dimensional axial-symmetry full particle-in-cell method was proposed to numerically simulate the ion beam neutralization process and near-field plume. The results indicate that, a high positive potential is formed in the ion beam near beam source, and it increases with time. The well of potential between this high positive potential and surround environment can limit the escape of electrons, and accelerate ions, making the two kinds of particles to possess the similar velocities, thus, the ion-electron coupling process, namely, the neutralization process, is completed. Additionally, during these processes, the kinetic energies of both electrons and ions increase along the advancing direction of plasma beam, while the electron temperature decreases.