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Global calculation of neoclassical impurity transport including the variation of electrostatic potential
Journal of Plasma Physics ( IF 2.5 ) Pub Date : 2020-06-25 , DOI: 10.1017/s0022377820000598
Keiji Fujita , S. Satake , R. Kanno , M. Nunami , M. Nakata , J. M. García-Regaña , J. L. Velasco , I. Calvo

Recently, the validity range of the approximations commonly used in neoclassical calculation has been reconsidered. One of the primary motivations behind this trend is observation of an impurity hole in LHD (Large Helical Device), i.e. the formation of an extremely hollow density profile of an impurity ion species, such as carbon $\text{C}^{6+}$ , in the plasma core region where a negative radial electric field ( $E_{r}$ ) is expected to exist. Recent studies have shown that the variation of electrostatic potential on the flux surface, $\unicode[STIX]{x1D6F7}_{1}$ , has significant impact on neoclassical impurity transport. Nevertheless, the effect of $\unicode[STIX]{x1D6F7}_{1}$ has been studied with radially local codes and the necessity of global calculation has been suggested. Thus, we have extended a global neoclassical code, FORTEC-3D, to simulate impurity transport in an impurity hole plasma including $\unicode[STIX]{x1D6F7}_{1}$ globally. Independently of the $\unicode[STIX]{x1D6F7}_{1}$ effect, an electron root of the ambipolar condition for the impurity hole plasma has been found by global simulation. Hence, we have considered two different cases, each with a positive (global) and a negative (local) solution of the ambipolar condition, respectively. Our result provides another support that $\unicode[STIX]{x1D6F7}_{1}$ has non-negligible impact on impurity transport. However, for the ion-root case, the radial $\text{C}^{6+}$ flux is driven further inwardly by $\unicode[STIX]{x1D6F7}_{1}$ . For the electron-root case, on the other hand, the radial particle $\text{C}^{6+}$ flux is outwardly enhanced by $\unicode[STIX]{x1D6F7}_{1}$ . These results indicate that how $\unicode[STIX]{x1D6F7}_{1}$ affects the radial particle transport crucially depends on the profile of the ambipolar- $E_{r}$ , which is found to be susceptible to $\unicode[STIX]{x1D6F7}_{1}$ itself and the global effects.

中文翻译:

新古典杂质输运的全局计算,包括静电势的变化

最近,重新考虑了新古典计算中常用的近似值的有效性范围。这一趋势背后的主要动机之一是观察 LHD(大螺旋装置)中的杂质空穴,即杂质离子种类(例如碳)的极其中空的密度分布的形成 $\文本{C}^{6+}$ , 在等离子体核心区域中,负径向电场 ( $E_{r}$ ) 预计存在。最近的研究表明,助焊剂表面静电势的变化, $\unicode[STIX]{x1D6F7}_{1}$ ,对新古典杂质传输有显着影响。尽管如此,效果 $\unicode[STIX]{x1D6F7}_{1}$ 已经用径向局部代码进行了研究,并提出了全局计算的必要性。因此,我们扩展了全球新古典代码 FORTEC-3D,以模拟杂质空穴等离子体中的杂质传输,包括 $\unicode[STIX]{x1D6F7}_{1}$ 全球范围内。独立于 $\unicode[STIX]{x1D6F7}_{1}$ 效应,通过全局模拟找到了杂质空穴等离子体双极条件的电子根。因此,我们考虑了两种不同的情况,每种情况分别具有双极性条件的正(全局)和负(局部)解。我们的结果提供了另一个支持,即 $\unicode[STIX]{x1D6F7}_{1}$ 对杂质迁移有不可忽视的影响。然而,对于离子根的情况,径向 $\文本{C}^{6+}$ 通量被进一步向内驱动 $\unicode[STIX]{x1D6F7}_{1}$ . 另一方面,对于电子根的情况,径向粒子 $\文本{C}^{6+}$ 通量向外增强 $\unicode[STIX]{x1D6F7}_{1}$ . 这些结果表明,如何 $\unicode[STIX]{x1D6F7}_{1}$ 影响径向粒子传输关键取决于双极性的轮廓 $E_{r}$ , 它被发现容易受到 $\unicode[STIX]{x1D6F7}_{1}$ 本身和全球影响。
更新日期:2020-06-25
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