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Observation of Interaction between Fast Ions and Turbulence in Large Helical Device

Hikona SAKAI¹⁾, Kenji TANAKA^1,2), Toshiki KINOSHITA¹⁾ and Kunihiro OGAWA^2,3)

1)

Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan

2)

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

3)

The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu 509-5292, Japan

(Received 9 January 2023 / Accepted 11 June 2023 / Published 25 September 2023)

Abstract

Systematic experiments were carried out in the 23rd Large Helical Device experiment campaign to explore the interaction between fast ions and ion-scale turbulence focusing on the impact of varying the power of the neutral beam (NB) injection. During the NB heating, two distinct phases of turbulence reduction were observed. The first phase was a transient reduction of about 10 msec immediately following the initiation of the NB injection. This reduction in turbulence was noticeable even while the electron density and temperature profiles remained nearly unchanged. The second phase involved a continuous reduction that maintained a lower turbulence level throughout the duration of the NB injection. The physics mechanisms underlying these phenomena are not fully understood yet. However, it is likely that two distinct processes of turbulence stabilization, each corresponding to the transient and continuous reduction phases, are at work due to the influence of the fast ions.

Copyright (c) 2023 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

plasma, turbulence, fast ions, interaction

DOI: 10.1585/pfr.18.2402069

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