Particle‐in‐cell/Monte Carlo simulation of electron and ion currents to cylindrical Langmuir probe
Particle‐in‐cell/Monte Carlo simulation of electron and ion currents to cylindrical Langmuir probe
复制标题
圆柱形朗缪尔探针的电子和离子电流的细胞内粒子/蒙特卡罗模拟
DOI：
10.1002/ctpp.201800063
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发表时间：
2018
影响因子：
1.6
通讯作者：
Z. Bonaventura
中科院分区：
文献类型：
--
作者：
P. Zikán;Kristián Farkaš;D. Trunec;J. Janský;Z. Bonaventura
利用粒子池/蒙特卡罗（PIC/MC）自一致模拟，计算了中性气体在2-3,000 Pa压力范围内的电子和离子流向圆柱形朗缪尔（静电）探针。当收集到的带电粒子与探针附近的中性气体粒子碰撞很重要时，模拟使我们能够在高中性气压力下计算探针电流。本文的主要目的是计算在这种高压下的探头电流，并将结果与实验测量的探头电流进行比较。在两种情况下进行了模拟：(a)在低中性气压力为2 Pa的高电子温度的非热等离子体中具有不同半径的探针（为了验证我们模拟的正确性），(b)在低电子温度和高中性气压力（高达3,000 Pa）的余热等离子体中具有10 μm半径的探针。在给定的等离子体条件下，情况(a)中得到的电子探针电流与轨道运动限制电流（OMLC）理论对半径为100 μm的探针的预测结果吻合得很好。在较大的探针半径和/或较高的探针电压下，OMLC理论错误地预测了过高的电子探针电流。此外，还推导了无碰撞情况下预鞘层中电子密度的空间依赖性公式。在较高的中性气体压力下的模拟，即情况(b)，显示了随着气体压力的增加和在探针周围形成一个大的预护套，电子探针电流降低。将模拟的电子探针电流与其他作者的测量结果进行了比较，并讨论了差异。
Electron and ion currents to a cylindrical Langmuir (electrostatic) probe were calculated using the particle‐in‐cell/Monte Carlo (PIC/MC) self‐consistent simulation for a neutral gas in the pressure range 2–3,000 Pa. The simulation enables us to calculate the probe currents even at high neutral gas pressures when the collisions of collected charged particles with neutral gas particles near the probe are important. The main aim of this paper is the calculation of probe currents at such high gas pressures and the comparison of the results with experimentally measured probe currents. Simulations were performed for two cases: (a) probes with varying radii in a non‐thermal plasma with high electron temperature at low neutral gas pressure of 2 Pa (in order to verify the correctness of our simulations), and (b) probe with the radius of 10 μm in the afterglow plasma with low electron temperature and a higher neutral gas pressure (up to 3,000 Pa). The electron probe currents obtained in case (a) show good agreement with those predicted by the orbital motion limited current (OMLC) theory for probes with radii up to 100 μm for the given plasma conditions. At larger probe radii and/or at higher probe voltages, the OMLC theory incorrectly predicts too high an electron probe current for the plasma parameters studied. Additionally, a formula describing the spatial dependence of the electron density in the presheath in the collisionless case is derived. The simulation at higher neutral gas pressures, i.e. case (b), shows a decrease of the electron probe current with increasing gas pressure and the creation of a large presheath around the probe. The simulated electron probe currents are compared with those of measurements by other authors, and the differences are discussed.