Plasma and Fusion Research

Volume 3, 030 (2008)

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 TOI1), Mitsutaka ISOBE1), Fumitake WATANABE, Chihiro SUZUKI1), Daiji KATO1), Kuninori SATO1) and LHD Experimental Group1)
Department of Energy Science and Engineering, Nagoya University, Nagoya 464-8603, Japan
1)
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
(Received 15 February 2008 / Accepted 3 May 2008 / Published 29 May 2008)

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.

Keywords

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

DOI: 10.1585/pfr.3.030

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This paper may be cited as follows:

Kunihiro OGAWA, Kazuo TOI, Mitsutaka ISOBE, Fumitake WATANABE, Chihiro SUZUKI, Daiji KATO, Kuninori SATO and LHD Experimental Group, Plasma Fusion Res. 3, 030 (2008).