Plasma and Fusion Research

Volume 14, 3403102 (2019)

Regular Articles

Global Effects on the Variation of Ion Density and Electrostatic Potential on the Flux Surface in Helical Plasmas

Keiji FUJITA¹⁾, Shinsuke SATAKE^1,2), Ryutaro KANNO^1,2), Masanori NUNAMI^1,2), Motoki NAKATA^1,2) and José Manuel GARCíA-REGAÑA³⁾

1): Department of Fusion Science, The Graduate University for Advanced Studies, 322-6 Oroshi-cho, Toki 509-5292, Japan
2): National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
3): Laboratorio Nacional de Fusión CIEMAT, 28040 Madrid, Spain

(Received 26 December 2018 / Accepted 22 April 2019 / Published 11 July 2019)

Abstract

Since the observation of impurity hole in LHD, which contradicts the prediction of the conventional neoclassical transport theory, several attempts have been made to explain the mechanism behind the phenomenon. Consideration of the impact of electrostatic potential variation within the flux surface, Φ₁, is one of those attempts. However, all of the numerical studies that have investigated the effect of Φ₁ to date have been conducted with local simulation codes, and no global calculation has been performed yet. Here, a global neoclassical simulation code FORTEC-3D is applied to evaluate Φ₁, including the global effects, for the first time. The global simulation result for a high-temperature low-density plasma, which corresponds to an impurity hole plasma, shows significant difference from the local simulation results in the Φ₁ profile. This indicates that consideration of the global effects is essential for quantitative evaluation of impurity neoclassical transport in an impurity hole plasma.

Keywords

neoclassical transport, impurity transport, stellarator

DOI: 10.1585/pfr.14.3403102

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