Plasma and Fusion Research

Volume 3, 033 (2008)

Rapid Communications

Excitation of Stable Alfvén Eigenmodes by Application of Alternating Magnetic Field Perturbations in the Compact Helical System
Takafumi ITO, Kazuo TOI1), Go MATSUNAGA2), Mitsutaka ISOBE1), Kenichi NAGAOKA1), Tsuyoshi AKIYAMA1), Takashi MINAMI1) and the CHS Experimental Group1)
Department of Energy Engineering and Science, Nagoya University,Furo-cho, Chikusa-ku, Nagoya City, Aichi 464-8601, Japan
1)
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan
2)
Japan Atomic Energy Agency, 801-1 Mukouyama, Naka, Ibaraki 311-0193, Japan
(Received 16 April 2008 / Accepted 7 May 2008 / Published 6 June 2008)

Abstract

Alternating magnetic perturbations, generated by external electrodes, are applied to a neutral-beam-heated plasma in the Compact Helical System, to excite stable Alfvén eigenmodes (AEs). Resonant peaks in the frequency range of the toroidal Alfvén eigenmode (TAE) have been observed in a transfer function defined by the ratio between the magnetic probe signal and the alternating electrode current. The resonant frequency fo agrees well with that of the TAE gap located near the plasma edge, where the strength of energetic ion drive of AEs will be sufficiently low. The damping rates γ derived from the width of the resonant peak are fairly large, i.e., γ/(2π fo) ∼ 20%.

Keywords

Alfvén eigenmodes, active sensing, frequency response analysis, mode damping rate, helical plasma

DOI: 10.1585/pfr.3.033

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References

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This paper may be cited as follows:

Takafumi ITO, Kazuo TOI, Go MATSUNAGA, Mitsutaka ISOBE, Kenichi NAGAOKA, Tsuyoshi AKIYAMA, Takashi MINAMI and the CHS Experimental Group, Plasma Fusion Res. 3, 033 (2008).