[Table of Contents]

Plasma and Fusion Research

Volume 3, S1067 (2008)

Regular Articles

Effect of Toroidal Current on Rotational Transform Profile by MHD Activity Measurement in Heliotron J
Gen MOTOJIMA, Satoshi YAMAMOTO1), Hiroyuki OKADA2), Satoru SAKAKIBARA3), Kiyomasa WATANABE3), Kazunobu NAGASAKI2), Yasuhiro SUZUKI3), Tohru MIZUUCHI2), Shinji KOBAYASHI2), Boyd D. BLACKWELL4), Yuji NAKAMURA, Katsumi KONDO, Kiyoshi HANATANI2), Hajime ARIMOTO, Shinya WATANABE and Fumimichi SANO2)
Graduate School of Energy Science, Kyoto University, Uji 611-0011, Japan
Kyoto University Pioneering Research Unit for Next Generation, Uji 611-0011, Japan
Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan
National Institute for Fusion Science, Toki 509-5292, Japan
Plasma Research Laboratory, Research School of Physical Sciences and Engineering, The Australian National University, Canberra ACT 0200, Australia
(Received 16 November 2007 / Accepted 4 February 2008 / Published 1 August 2008)


The effect of toroidal current on the rotational transform was investigated in Heliotron J by measuring magnetohydrodynamic (MHD) activities at two configurations with a rotational transform (ι/2π) close to 0.5. The resonant m/n = 2/1 mode was observed in an ECH + co-NBI plasma in the configuration with ι/2π = 0.48 at ρ = 0.7. Here, m and n are the poloidal and toroidal mode numbers, respectively. ρ is the normalized minor radius. The rotational transform is increased presumably due to the toroidal current. The location of the ι/2π = 0.50 rational surface was determined to be ρ = 0.8-0.9 by soft X-ray (SX) fluctuations related to the MHD mode. An equilibrium calculation considering the toroidal current showed that the increase in the rotational transform due to the toroidal current was consistent with experimental results. The resonant mode structure was also investigated in an ECH + counter-NBI plasma at the ι/2π = 0.50 configuration. The location of the ι/2π = 0.50 rational surface, as determined by SX signals, did not change significantly compared with that obtained under a vacuum configuration. There is no significant difference between the rotational transform profile that considers toroidal currents by equilibrium calculation and that of the vacuum configuration. These results suggest that the change in the rotational transform profile caused by the toroidal current was small, owing to the balance between the bootstrap current and counter-flowing NB driven current.


bootstrap current, NB driven current, MHD instability, magnetic fluctuation, Heliotron J

DOI: 10.1585/pfr.3.S1067


  • [1] T. Obiki et al., Nucl. Fusion 41, 833 (2001).
  • [2] S. Yamamoto et al., Fusion Sci. Technol. 51, 92 (2007).
  • [3] G. Motojima et al., Nucl. Fusion 47, 1045 (2007).
  • [4] G. Motojima et al., Fusion Sci. Technol. 51, 122 (2007).
  • [5] S. Sakakibara et al., Jpn. J. Appl. Phys. 34, L252 (1995).
  • [6] E. Sallander et al., Nucl. Fusion 40, 1499 (2000).
  • [7] F. Sano et al., Nucl. Fusion 45, 1557 (2005).
  • [8] S. Kobayashi et al., Proc. 34th EPS Conf. on plasma Phys. Warsaw, ECA 31F, P-4. 162 (2007); also available at http://epsppd.epfl.ch/Warsaw/pdf/P4_162.pdf
  • [9] S.P. Hirshman and O. Betancourt, J. Comput. Phys. 96, 99 (1991).

This paper may be cited as follows:

Gen MOTOJIMA, Satoshi YAMAMOTO, Hiroyuki OKADA, Satoru SAKAKIBARA, Kiyomasa WATANABE, Kazunobu NAGASAKI, Yasuhiro SUZUKI, Tohru MIZUUCHI, Shinji KOBAYASHI, Boyd D. BLACKWELL, Yuji NAKAMURA, Katsumi KONDO, Kiyoshi HANATANI, Hajime ARIMOTO, Shinya WATANABE and Fumimichi SANO, Plasma Fusion Res. 3, S1067 (2008).