LIPS-200离子推力器放电室原初电子动力学行为的数值模拟研究

Investigation on Dynamical Behavior of Primary Electrons in LIPS-200 Ion Thruster Discharge Chamber

关键词:  LIPS-200  离子推力器  放电室  原初电子  PIC/MCC数值模拟

Key words:  LIPS-200  Ion thruster  Discharge chamber  Primary electron  PIC/MCC model

摘要:

为了得到试验测量不到的气体放电过程中电磁场作用下单个原初电子的动力学行为，建立了LIPS-200离子推力器放电室二维仿真模型，应用网格粒子法(PIC)和蒙特卡洛碰撞(MCC)模拟法对其进行了研究。模拟得到在额定工况下原初电子和中性原子之间的碰撞概率、原初电子损耗率、电磁场分布对其运动速度及运动轨迹的影响等。结果表明磁铁表面磁感强度最大，越靠近放电室内部磁感强度越小，对称轴区域无磁场分布，原初电子在电磁场作用下沿磁力线作加速螺旋运动；运动等离子体的自洽电势大小范围仅为0~2.0V，几乎不会影响等离子体运动；对应总原初电子个数为1.2×106时直接被阳极表面吸收的损耗率仅为0.02%。

Abstract:

In order to obtain the dynamic behavior of primary electrons that cannot be measured in the ion thruster discharge chamber， a 2D axis symmetric PIC/MCC model is established by using the PIC/MCC simulation. The collisional probabilities between the electrons and neutral atoms， the loss rate of the electrons， the effects of electromagnetic field in the chamber on the velocity and the trajectory of the primary electron are analyzed. The simulation results show that the maximal magnetic field locates at the surface of the permanent magnets. The magnetic field decreases exponentially away from the wall all along the boundary. Dynamic potential induced by space charges is about 0~2.0V， which is so small that cannot affect the dynamical behavior of the primary electron. Motion of a particle along the magnetic field is not affected by this field，however， it causes the particle motion to form a helix along with a radius given by the Larmor radius. Electron loss increases exponentially with the total number of the primary electrons. While the total number of the primary electron is about 1.2×106， its loss rate is only 0.02%