PIC仿真增大真空介电常数对等离子体周向波的影响
The Influence of Increasing Vacuum Dielectric Constant on Plasma Azimuthal Wave in PIC Simulation

在霍尔推力器全粒子PIC (Particle in cell)模拟方法中，常常采用增大真空介电常数的方法来增大等离子体德拜长度，进而在划分网格时可以将网格尺寸放大，减小网格数量从而达到减小计算量的目的。但由等离子体形成的周向振荡对真空介电常数变化反应比较敏感，相应等离子体参数随真空介电常数的变化是否符合离子声波色散规律需要得到验证。本文以2.5D-3V的霍尔推力器周向–径向模型为基础，通过改变真空介电常数放大倍数对等离子体分布情况、空间电势分布情况及模拟所得离子声波参数与理论值对比发现：在研究霍尔推力器等离子体周向振荡相关问题时，真空介电常数扩大倍数越大，所得周向波参数与理论估算值偏差越大，原则上不宜采用真空介电常数扩大的方法进行模拟，若所研究区域范围较大，可适当扩大真空介电常数至4倍以内。
In the PIC (particle in cell) of Hall thruster, increasing the dielectric constant of vacuum is often used to increase the Debye length of plasma, and then the mesh size can be enlarged and the num-ber of meshes can be reduced to reduce the calculation amount. However, the azimuthal oscillation formed by the plasma is sensitive to the change of the vacuum dielectric constant. Whether the change of the corresponding plasma parameters with the vacuum dielectric constant conforms to the law of ion acoustic dispersion needs to be verified. This paper is based on the circumferential and radial model of hall thruster of 2.5D-3V. By changing the amplification factor of the vacuum di-electric constant, the plasma distribution, the space potential distribution and the simulated ion acoustic wave parameters were compared with the theoretical values, and it was found that: the larger the amplification of vacuum dielectric constant is, the larger the azimuthal wave parameters are. In principle, it is not suitable to use the method of expanding the vacuum dielectric constant to simulate the larger deviation from the theoretical estimate. If the research area is large, it can be appropriately expanded to within 4 times.