Plasma and Fusion Research

Volume 11, 2402106 (2016)

Regular Articles

Comparison of Ion Internal Transport Barrier Formation between Hydrogen and Helium Dominated Plasmas

Kenichi NAGAOKA^1,2), Hiromi TAKAHASHI^1,2), Kenji TANAKA¹⁾, Masaki OSAKABE^1,2), Sadayoshi MURAKAMI³⁾, Shogo MAETA³⁾, Masayuki YOKOYAMA¹⁾, Keisuke FUJII⁴⁾, Haruhisa NAKANO^1,2), Hiroshi YAMADA^1,2), Yasuhiko TAKEIRI^1,2), Katsumi IDA^1,2), Mikiro YOSHINUMA^1,2) and the LHD Experiment Group

1): National Institute for Fusion Science, Toki 509-5292, Japan
2): SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292, Japan
3): Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501, Japan
4): Department of Mechanical Engineering and Science, Kyoto University, Kyoto 615-8540, Japan

(Received 9 December 2015 / Accepted 22 June 2016 / Published 16 September 2016)

Abstract

Ion internal transport barrier (ITB) was formed in both hydrogen discharge and helium dominated discharge. The central ion temperature was investigated as a function of the hydrogen density ratio (n_H/(n_H+n_He)). The central ion temperature increases with the decrease of the hydrogen density ratio, while the electron temperature does not change significantly. The experimentally observed ion temperature was not reproduced by the prediction of TASK-3D modeling. The dominant activity in the density fluctuation measured by the phase contrast imaging is consistent with ion temperature gradient mode and they are almost identical between the hydrogen dominated and helium dominated plasmas.

Keywords

ion ITB, helical plasma, isotope effect, deuterium experiment

DOI: 10.1585/pfr.11.2402106

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