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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 the structure of the ion thruster, the physical mechanism of the ion-electron coupling and the formation process of the neutral plasma during the neutralization of the ion thruster was studied. The ion beam neutralization process and near-field plume are numerically simulated by 2-dimensional axisymmetric full-particle particle grid method. The results show that a higher positive potential is formed in the ion beam near the exit of the thruster and the positive potential is gradually increased over time. The potential well formed between the high potential at the exit of the thruster and the surrounding environment can limit the escape of electrons and accelerate the ions, and finally make the velocity of the two converge to complete the ion-electron coupling process, that is, the ion beam neutralization process . In the above process, the kinetic energy of the electrons and ions along the direction of advancement of the plasma beam increases, and the thermal energy of the electrons decreases.