Measurement of Radial Structure of Energetic-Ion-Driven MHD Modes with a Fast Response Hα-Detector Array in the Large Helical Device

Kunihiro OGAWA; Kazuo TOI; Mitsutaka ISOBE; Fumitake WATANABE; Chihiro SUZUKI; Daiji KATO; Kuninori SATO; LHD Experimental Group

doi:10.1585/pfr.3.030

Rapid Communications

Measurement of Radial Structure of Energetic-Ion-Driven MHD Modes with a Fast Response Hα-Detector Array in the Large Helical Device

Kunihiro OGAWA, Kazuo TOI, Mitsutaka ISOBE, Fumitake WATANABE, Chihiro SUZUKI, Daiji KATO, Kuninori SATO, LHD Experimental Group

Author information

Kunihiro OGAWA
Department of Energy Science and Engineering, Nagoya University, Nagoya 464-8603, Japan
Kazuo TOI
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
Mitsutaka ISOBE
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
Fumitake WATANABE
Department of Energy Science and Engineering, Nagoya University, Nagoya 464-8603, Japan
Chihiro SUZUKI
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
Daiji KATO
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
Kuninori SATO
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
LHD Experimental Group
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

Keywords: Alfvén eigenmode (AE), fast-response Hα detector, correlation analysis, radial structure, TAE

JOURNAL FREE ACCESS

2008 Volume 3 Pages 030

DOI https://doi.org/10.1585/pfr.3.030

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Abstract

In the Large Helical Device, coherent fluctuations related to energetic-ion-driven magneto-hydrodynamic (MHD) instabilities such as Alfvén eigenmodes (AEs) were detected for the first time using an Hα detector array having high-frequency response up to 200 kHz. Correlation analysis between detector and magnetic probe signals has enabled us to successfully extract coherent fluctuations in the AE frequency range. The radial profile of the excess of the coherence from the background value (Δγ) has a clear peak around the predicted toroidal Alfvén eigenmode (TAE) gap.

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