Abstract The wide application of ion sources requires the optimization of the ion optics to achieve a balance between the performance, life cycle and size. A 2D hybrid model is represented to simulate the ion optics for positive ion extraction where adaptive particle management and parallel computing are considered. Then, misunderstandings and inconsistencies in the previous numerical models of positive ion extraction are discussed, and new methods for determining the key simulation parameters are proposed. The local model of positive ion extraction is found to be unable to form a presheath and simulate a Bohm sheath self-consistently, which indicates that the upstream surface of the numerical domain should be the sheath edge and the simulation parameters should satisfy the sheath characteristics. Accordingly, the methods for determining the length of the upstream domain, the potential of the upstream surface and the injection of ions are discussed, as well as the effects of key parameters on the simulation results. Further simulations demonstrate that the thermal velocities of ions can affect the perveance condition of the ion beamlet. By comparing the simulation results with earlier experimental results, it is shown that our 2D model can describe the beam divergence characteristics correctly and predict the perveance limit well with high computational efficiency.

中文翻译：

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正离子提取数值模拟中的问题

摘要 离子源的广泛应用需要对离子光学器件进行优化，以实现性能、寿命周期和尺寸之间的平衡。2D 混合模型被表示为模拟用于正离子提取的离子光学，其中考虑了自适应粒子管理和并行计算。然后，讨论了先前正离子提取数值模型中存在的误解和不一致之处，并提出了确定关键模拟参数的新方法。发现正离子提取局部模型不能形成预鞘，自洽模拟玻姆鞘，说明数值域的上游面应为鞘边缘，模拟参数应满足鞘特性。因此，讨论了确定上游域长度、上游表面电位和离子注入的方法，以及关键参数对模拟结果的影响。进一步的模拟表明，离子的热速度会影响离子子束的渗透条件。通过将仿真结果与早期实验结果进行比较，表明我们的二维模型可以正确地描述光束发散特性，并以较高的计算效率很好地预测渗透极限。