Plasma and Fusion Research

Volume 16, 2402052 (2021)

Regular Articles

Analysis of NB Fast-Ion Loss Mechanisms in MHD Quiescent LHD Plasmas
Hideo NUGA1), Ryohsuke SEKI1,2), Kunihiro OGAWA1,2), Shuji KAMIO1), Yutaka FUJIWARA1), Hiroyuki YAMAGUCHI1,2), Masaki OSAKABE1,2), Mitsutaka ISOBE1,2), Sadayoshi MURAKAMI3) and Masayuki YOKOYAMA1,2)
1)
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki 509-5292, Japan
2)
The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan
3)
Department of Nuclear Engineering, Kyoto University, Nishikyo, Kyoto 615-8540, Japan
(Received 4 December 2020 / Accepted 10 February 2021 / Published 21 April 2021)

Abstract

Neutral beam (NB) fast-ion loss mechanisms in the large helical device (LHD) are investigated by the combination of the neutron measurement, the classical slowing-down simulation, and the neo-classical guiding center orbit following simulation. It is found that the neo-classical transport provides little contribution to the loss of tangentially injected NB fast-ions. For perpendicularly injected NB fast-ions, the neo-classical transport has more than 40% contribution to the NB fast ion loss. These results indicate that there are other loss mechanisms dominant in LHD plasmas. The charge exchange loss is one of the plausible candidates for the loss mechanism.

Keywords

fast ion confinement, neo-classical transport, charge exchange

DOI: 10.1585/pfr.16.2402052

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