EFFECT OF DEUTERIUM PLASMAS ON CARBON IMPURITY TRANSPORT IN THE EDGE STOCHASTIC MAGNETIC FIELD LAYER OF LARGE HELICAL DEVICE
EFFECT OF DEUTERIUM PLASMAS ON CARBON IMPURITY TRANSPORT IN THE EDGE STOCHASTIC MAGNETIC FIELD LAYER OF LARGE HELICAL DEVICE
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发表时间：
2018
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通讯作者：
T. Oishi;S. Morita;M. Kobayashi;G. Kawamura;Y. Liu;M. Goto
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作者：
T. Oishi;S. Morita;M. Kobayashi;G. Kawamura;Y. Liu;M. Goto
大型螺旋器件(LHD)的遍历层是由螺旋线圈形成的具有三维结构的随机磁场组成的。在LHD中研究了减少遍历层中平行的杂质输运，即所谓的“杂质屏蔽”。本文将碳杂质的空间分辨真空紫外光(VUV)光谱应用于氘(D)等离子体，以阐明体离子质量对杂质在遍历层中输运的影响。利用3m垂直入射真空紫外光谱仪，在边缘等离子体水平拉伸位置测量了二阶CIV谱线发射(2×1548.20？)的多普勒剖面。在接近遍历层最外层的位置处，流速变为最大值。用三维数值模拟程序EMC3-Eirene计算的平行动量平衡中的摩擦力与观测到的流动方向一致。在氢(H)等离子体中，流动速度随电子密度的增加而增加。模拟结果支持了摩擦力在高密度区的力平衡中占主导地位的预测。这导致了杂质流动的增加，从而促进了杂质筛选。另一方面，在D等离子体中的流动速度小于在H等离子体中的流动速度。当动量平衡中摩擦力项占主导地位时，体离子热速度的质量依赖性可能是D和H等离子体流量值不同的原因之一。
The ergodic layer of Large Helical Device (LHD) consists of stochastic magnetic fields with three-dimensional structure intrinsically formed by helical coils. Reduction of the parallel impurity transport in the ergodic layer, so called “impurity screening”, has been studied in LHD. In the paper, the space-resolved vacuum ultraviolet (VUV) spectroscopy for carbon impurities is applied to deuterium (D) plasmas to clarify the effect of the bulk ion mass on the impurity transport in the ergodic layer. Doppler profile measurement at the second order of CIV line emission (2 × 1548.20 Å) is attempted using a 3 m normal incidence VUV spectrometer in the edge plasma at a horizontally-elongated plasma position. The flow velocity becomes the maximum value at the position close to the outermost region of the ergodic layer. The direction of the observed flow is same as the friction force in the parallel momentum balance calculated with a three-dimensional simulation code, EMC3-EIRENE. The flow velocity increases with the electron density in the hydrogen (H) plasmas. The result supports a prediction from the simulation that the friction force becomes more dominant in the force balance in higher density regime. It leads to the increase in the impurity flow which can develop the impurity screening. On the other hand, the flow velocity in the D plasma is smaller than that in the H plasma. The mass dependence of the thermal velocity of the bulk ions could be one of the reasons for the difference of the flow values between D and H plasmas when the friction force term is dominant in the momentum balance.