Plasma and Fusion Research

Volume 1, 004 (2006)

Rapid Communications

Observation of Minor Collapse of Current-Carrying Plasma in LHD
Yoshiro NARUSHIMA1), Satoru SAKAKIBARA1), Kiyomasa WATANABE1), Katsumi IDA1), Kazumichi NARIHARA1), Satoshi OHDACHI1), Shigeru INAGAKI1), Mikio YOSHINUMA1), Ichihiro YAMADA1), Wilfred A. COOPER3), Hiroshi YAMADA1), Taiki YAMAGUCHI2), Yasuhiko TAKEIRI1) and LHD Experimental Group1)
1)
National Institute for Fusion Science
2)
Department of Fusion Science, Graduate University for Advanced Studies
3)
CRPP Association Euratom / Confederation Suisse, EPFL
(Received 22 November 2005 / Accepted 23 December 2005 / Published 27 January 2006)

Abstract

A minor collapse observed in current-carrying plasma has been investigated in Large Helical Device (LHD). The magnetic configuration with high central rotational transform has ι/2π = 1 surface at the core region and is relatively unstable for the m/n = 1/1 mode (here, m and n are the poloidal and toroidal mode number, respectively). When the beam-driven current exceeds a certain value, the m/n = 1/1 mode grows with a growth time of ˜30 ms and causes a sudden drop of the plasma stored energy and the electron temperature, and it also limits the plasma current itself. A local flattening in an electron temperature profile appears just after the minor collapse. The mode does not rotate and stays at the same spatial location. The possibility of pressure- and current-driven magneto-hydro dynamics (MHD) instabilities is discussed.

Keywords

Large Helical Device, MHD instability, plasma current

DOI: 10.1585/pfr.1.004

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References

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This paper may be cited as follows:

Yoshiro NARUSHIMA, Satoru SAKAKIBARA, Kiyomasa WATANABE, Katsumi IDA, Kazumichi NARIHARA, Satoshi OHDACHI, Shigeru INAGAKI, Mikio YOSHINUMA, Ichihiro YAMADA, Wilfred A. COOPER , Hiroshi YAMADA, Taiki YAMAGUCHI, Yasuhiko TAKEIRI and LHD Experimental Group, Plasma Fusion Res. 1, 004 (2006).