Regular Articles

Full Text / References

Mode Structure of Locked-Mode-Like Instability in LHD and Its Effects on Confinement Degradation

Yuki TAKEMURA^1,2), Ryo YASUHARA^1,2), Hisamichi FUNABA¹⁾, Hiyori UEHARA^1,2), D. J. Den HARTOG³⁾, Kiyomasa WATANABE^1,4), Satoru SAKAKIBARA^1,2), Yoshiro NARUSHIMA^1,2) and Satoshi OHDACHI^1,5)

1)

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

2)

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

3)

University of Wisconsin-Madison, Department of Physics, Madison, Wisconsin, USA

4)

Nagoya University, Graduate School of Engineering, Chikusa, Nagoya 464-8603, Japan

5)

The University of Tokyo, Graduate School of Frontier Sciences, Kashiwa, Chiba 277-8561, Japan

(Received 20 April 2021 / Accepted 24 June 2021 / Published 2 August 2021)

Abstract

The internal mode structure of a precursor with the tearing-parity structure of the locked-mode-like instability is investigated. For the first time, the Thomson scattering system with high temporal and spatial resolution enables us to find the non-rotating temperature flattening region in the torus outboard side in addition to the rotating island during the slowing-down phase. Additionally, the width of the flattening region is 10% normalized by the plasma minor radius. Furthermore, the radial profiles of the pressure degradation during the slowing-down phase are evaluated. At the beginning of the slowing-down phase, the pressure degradation area is located slightly inside the resonant surface. After that, the peak location moves to the core region. Finally, the degradation area peaks at the plasma center.

Copyright (c) 2021 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

locked mode, magnetic island, ideal interchange mode, MHD instability, LHD

DOI: 10.1585/pfr.16.1402091

Full Text

PDF format (790Kbytes)

References

• [1] Y. Takemura et al., Nucl. Fusion 52, 102001 (2012).
• [2] S. Sakakibara et al., Nucl. Fusion 55, 083020 (2015).
• [3] S. Sakakibara et al., Nucl. Fusion 53, 043010 (2013).
• [4] M. Okamoto et al., Nucl. Fusion 61, 046005 (2021).
• [5] Y. Takemura et al., Nucl. Fusion 59, 066036 (2019).
• [6] Y. Takemura et al., Plasma Fusion Res. 12, 1402028 (2017).
• [7] T. Tokuzawa et al., Nucl. Fusion 57, 076003 (2017).
• [8] Y. Takemura et al., Nucl. Fusion 61, 026011 (2021).
• [9] I. Yamada et al., Fusion Sci. Technol. 58, 345 (2010).
• [10] K.Y. Watanabe et al., Fusion Sci. Technol. 58, 160 (2010).
• [11] T. Morisaki et al., Fusion Sci. Technol. 58, 465 (2010).
• [12] S. Sakakibara and H. Yamada, Fusion Sci. Technol. 1055, 471 (2010).
• [13] H. Johnsen et al., Phys. Fluids 30, 2239 (1987).