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Turbulent impurity transport simulations in Wendelstein 7-X plasmas
Journal of Plasma Physics ( IF 2.1 ) Pub Date : 2021-02-02 , DOI: 10.1017/s0022377820001543
J. M. García-Regaña , M. Barnes , I. Calvo , F. I. Parra , J. A. Alcusón , R. Davies , A. González-Jerez , A. Mollén , E. Sánchez , J. L. Velasco , A. Zocco

A study of turbulent impurity transport by means of quasilinear and nonlinear gyrokinetic simulations is presented for Wendelstein 7-X (W7-X). The calculations have been carried out with the recently developed gyrokinetic code stella. Different impurity species are considered in the presence of various types of background instabilities: ion temperature gradient (ITG), trapped electron mode (TEM) and electron temperature gradient (ETG) modes for the quasilinear part of the work; ITG and TEM for the nonlinear results. While the quasilinear approach allows one to draw qualitative conclusions about the sign or relative importance of the various contributions to the flux, the nonlinear simulations quantitatively determine the size of the turbulent flux and check the extent to which the quasilinear conclusions hold. Although the bulk of the nonlinear simulations are performed at trace impurity concentration, nonlinear simulations are also carried out at realistic effective charge values, in order to know to what degree the conclusions based on the simulations performed for trace impurities can be extrapolated to realistic impurity concentrations. The presented results conclude that the turbulent radial impurity transport in W7-X is mainly dominated by ordinary diffusion, which is close to that measured during the recent W7-X experimental campaigns. It is also confirmed that thermodiffusion adds a weak inward flux contribution and that, in the absence of impurity temperature and density gradients, ITG- and TEM-driven turbulence push the impurities inwards and outwards, respectively.

中文翻译:

Wendelstein 7-X 等离子体中的湍流杂质传输模拟

通过准线性和非线性陀螺动力学模拟对Wendelstein 7-X (W7-X) 的湍流杂质传输进行了研究。计算是使用最近开发的旋动代码 stella 进行的。在存在各种类型的背景不稳定性的情况下考虑不同的杂质种类:工作的准线性部分的离子温度梯度(ITG)、俘获电子模式(TEM)和电子温度梯度(ETG)模式;非线性结果的 ITG 和 TEM。虽然准线性方法允许人们得出关于对通量的各种贡献的符号或相对重要性的定性结论,但非线性模拟定量地确定湍流通量的大小并检查准线​​性结论的适用程度。尽管大部分非线性模拟是在痕量杂质浓度下进行的,但非线性模拟也在实际有效电荷值下进行,以便了解基于对痕量杂质进行的模拟得出的结论在多大程度上可以外推到实际杂质浓度. 所呈现的结果得出结论,W7-X 中的湍流径向杂质传输主要由普通扩散控制,这与最近 W7-X 实验活动中测量的结果接近。还证实热扩散增加了微弱的向内通量贡献,并且在没有杂质温度和密度梯度的情况下,ITG 和 TEM 驱动的湍流分别将杂质向内和向外推。非线性模拟也在实际的有效电荷值下进行,以便了解基于对痕量杂质进行的模拟得出的结论在多大程度上可以外推到实际的杂质浓度。所呈现的结果得出结论,W7-X 中的湍流径向杂质传输主要由普通扩散控制,这与最近 W7-X 实验活动中测量的结果接近。还证实热扩散增加了微弱的向内通量贡献,并且在没有杂质温度和密度梯度的情况下,ITG 和 TEM 驱动的湍流分别将杂质向内和向外推。非线性模拟也在实际的有效电荷值下进行,以便了解基于对痕量杂质进行的模拟得出的结论在多大程度上可以外推到实际的杂质浓度。所呈现的结果得出结论,W7-X 中的湍流径向杂质传输主要由普通扩散控制,这与最近 W7-X 实验活动中测量的结果接近。还证实热扩散增加了微弱的向内通量贡献,并且在没有杂质温度和密度梯度的情况下,ITG 和 TEM 驱动的湍流分别将杂质向内和向外推。为了了解基于对痕量杂质进行的模拟得出的结论在多大程度上可以外推到实际的杂质浓度。所呈现的结果得出结论,W7-X 中的湍流径向杂质传输主要由普通扩散控制,这与最近 W7-X 实验活动中测量的结果接近。还证实热扩散增加了微弱的向内通量贡献,并且在没有杂质温度和密度梯度的情况下,ITG 和 TEM 驱动的湍流分别将杂质向内和向外推。为了了解基于对痕量杂质进行的模拟得出的结论在多大程度上可以外推到实际的杂质浓度。所呈现的结果得出结论,W7-X 中的湍流径向杂质传输主要由普通扩散控制,这与最近 W7-X 实验活动中测量的结果接近。还证实热扩散增加了微弱的向内通量贡献,并且在没有杂质温度和密度梯度的情况下,ITG 和 TEM 驱动的湍流分别将杂质向内和向外推。
更新日期:2021-02-02
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