电子温度对霍尔推进器等离子体鞘层特性的影响

采用二维粒子模拟方法研究了霍尔推进器通道中电子温度对等离子体鞘层特性的影响, 讨论了不同电子温度下电子数密度、鞘层电势、电场及二次电子发射系数的变化规律. 结果表明: 当电子温度较低时, 鞘层中电子数密度沿径向方向呈指数下降, 在近壁处达到最小值, 鞘层电势降和电场径向分量变化均较大, 壁面电势维持一稳定值不变, 鞘层稳定性好; 当电子温度较高时, 鞘层区内与鞘层边界处电子数密度基本相等, 而在近壁面窄区域内迅速增加, 壁面处达到最大值, 鞘层电势变化缓慢, 电势降和电场径向分量变化均较小, 壁面电势近似维持等幅振荡, 鞘层稳定性降低; 电子温度对电场轴向分量影响较小; 随电子温度的增大, 壁面二次电子发射系数先增大后减少. 关键词： 霍尔推进器 等离子体鞘层 电子温度 粒子模拟

Effect of electron temperature on the characteristics of plasma sheath in Hall thruster

In this paper, the effect of electron temperature on the characteristics of plasma sheath in the channel of Hall thruster is studied by using two-dimensional (2D) particle-in-cell simulation method. The change laws of electron number density, sheath potential, electric field and secondary electron emission coefficient at different electron temperatures are discussed. The results show that when the electron temperature is low, electron number density decreases exponentially in the radial direction and reaches a minimum at the wall, the sheath potential drops and variation of electric field in the radial direction is larger, and the wall potential stays at a stable value, the stability of sheath is better. However, when the electron temperature is high, the electron number density inside the sheath region approximates to that at the sheath boundary, but in a narrow area near the wall it increases rapidly and reaches a maximum at the wall, sheath potential changes slowly, the sheath potential drops and variation of electric field in the radial direction is smaller, and the wall potential tends to maintain a persistent oscillation and the stability of sheath is reduced. The influence of electron temperature on electric field in the axial direction is small. With the increase of the electron temperature, wall secondary electron emission coefficient increases in the early stage, and reduces later.
Keywords： Hall thruster plasma sheath electron temperature particle in cell