Particle-in-cell simulations of heat flux to tokamak divertors in an oblique magnetic field
Particle-in-cell simulations of heat flux to tokamak divertors in an oblique magnetic field
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DOI：
10.1088/1361-6587/abe6b6
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发表时间：
2021-02
影响因子：
2.2
通讯作者：
Zongzheng Men;N. Xiang;J. Ou;Xueyi Wang
中科院分区：
文献类型：
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作者：
Zongzheng Men;N. Xiang;J. Ou;Xueyi Wang
托卡马克偏滤器过多热通量的管理是最重要的问题之一，特别是对于 EAST 的长脉冲运行。人们开发了主要基于流体模型的不同模拟代码来研究边缘等离子体中的物理过程，包括偏滤器目标板的热通量。在这些模拟中，仅包括中性区域，并使用基于简化护套模型的能量传输系数来估计热通量。在本文中，通过考虑鞘层，进行细胞内颗粒模拟来研究流向 EAST 偏滤器目标板的热通量。研究发现，鞘层中的平行电子速度分布函数（VDF）是截止麦克斯韦分布，因此可以解析地获得电子鞘层能量传输，而鞘层中的离子VDF强烈依赖于磁场和偏滤器靶板之间的入射角。对于较小的入射角，在鞘层中，离子沿开放轨道运动，并由于洛伦兹力而主要在垂直于磁场和靶板形成的平面的方向上加速。给出了靶板离子热通量的解析表达式，所得结果与模拟结果非常吻合。
The management of excessive heat flux to tokamak divertors is one of the most important issues, especially for long-pulse operations of EAST. Different simulation codes based mainly on fluid models have been developed to study the physical processes in edge plasma, including the heat flux to divertor target plates. In these simulations, only the neutral region is included and the heat flux is estimated by using energy transmission coefficients based on a simplified sheath model. In this paper, particle-in-cell simulations are conducted to study the heat flux flowing to the EAST divertor target plates by taking the sheath into account. It is found that the parallel electron velocity distribution function (VDF) in the sheath is a cut-off Maxwellian distribution so the electron sheath energy transmission can be obtained analytically, while ion VDFs in the sheath strongly depend on the incident angle between the magnetic field and divertor target plates. For a small incident angle, in the sheath, the ions move along open orbits and are accelerated mainly in the direction perpendicular to the plane formed by the magnetic field and target plates due to the Lorentz force. An analytical expression for the ion heat flux to the target plates is presented and the obtained results are in good agreement with the simulation results.