论文标题
在低温EXB等离子体中发言。从梯度 - 饮用不稳定到电离波的过渡
Spoke formation in low temperature ExB plasmas. Transition from gradient-drift instability to ionization wave
论文作者
论文摘要
在霍尔推进器或磁铁放电的许多实验中，已经观察到在方位角旋转的长波长等离子体非均匀性（“旋转辐条”）。我们使用二维（2D），轴向 - 齐路粒子粒子中的蒙特卡洛碰撞（PIC-MCC）模型在接近最近实验的条件下，在直流电流（DC）磁控杆排放中的不稳定性形成。 尽管模型的简化了2D几何形状，但模拟仍可以重现实验结果的主要特征。在阴极上方的给定位置，对应于辐条位置，模拟显示了血浆密度的幅度振幅较大，并且在辐条的前沿处的血浆电势和电子温度的急剧升高，因为随着时间的推移探测测量值。此外，模拟表明，不稳定性从线性相中的梯度拖延类型的不稳定类型演变为非线性相的电离波，在第一阶段和第二阶段的-EXB方向旋转，在第二阶段旋转。在实验中，发现辐条的数量随压力增加而增加。讨论了电子加热的机制以及BX $ \ nabla $ b在电子加热中以及在辐条旋转的相干和方向中的作用。
Long wavelength plasma non-uniformities rotating in the azimuthal direction ("rotating spokes") have been observed in a number of experiments on Hall thrusters or magnetron discharges. We use a two-dimensional (2D), axial-azimuthal Particle-In-Cell Monte Carlo Collisions (PIC-MCC) model to study the formation of instabilities in a direct current (dc) magnetron discharge under conditions close to recent experiments. In spite of the simplified 2D geometry of the model, the simulations can reproduce the main features of the experimental results. At a given position above the cathode, corresponding to the spoke location, the simulations show large amplitude oscillations of the plasma density and a very sharp increase of the plasma potential and electron temperature at the leading edge of the spoke, as in time resolved probe measurements. Moreover, the simulations show that the instability evolves in time from a gradient-drift type of instability in the linear phase, to an ionization wave in the non-linear phase, with rotation in the +ExB direction in the first phase and in the -ExB direction in the second phase. The number of spokes is found to increase with pressure, as in experiments. The mechanisms of electron heating and the role of the Bx$\nabla$B drift in electron heating and in the coherence and direction of spoke rotation are discussed.
