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Onset and Evolution of m/n = 2/1 Neoclassical Tearing Modes in High-β_p Mode Discharges in JT-60U

Akihiko ISAYAMA, Go MATSUNAGA, Yoichi HIRANO¹⁾ and the JT-60 Team

Japan Atomic Energy Agency, Naka, Ibaraki 311-0193, Japan

1)

Nihon University, 1-8-14 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308, Japan

(Received 2 October 2012 / Accepted 27 December 2012 / Published 27 March 2013)

Abstract

The onset and evolution of an m/n = 2/1 neoclassical tearing mode (NTM) in JT-60U under nearly constant discharge conditions are investigated (m and n are the poloidal and toroidal mode numbers, respectively.). In about 80% of the discharges, the 2/1 NTM appears from a small amplitude without a noticeable triggering event, and in the rest of the discharges, the 2/1 NTM is triggered by a collapse localized at the mode location. Although the former grows with regular oscillations of the magnetic perturbations, the latter grows with irregular oscillations from the beginning. In addition, although a collapse causing a temperature change of ∼20% triggers a 2/1 NTM, a smaller-amplitude collapse, e.g., a temperature change of ∼7%, does not trigger an NTM. This suggests the existence of a threshold amplitude that triggers an NTM. The characteristics of the localized collapse are similar to those of a previously observed barrier localized mode.

Copyright (c) 2013 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

neoclassical tearing mode, instability, JT-60U, tokamak

DOI: 10.1585/pfr.8.1402013

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References

• [1] T.C. Hender, J.C. Wesley, J. Bialek et al., Nucl. Fusion 47, S128 (2007).
• [2] H. Zohm, G. Gantenbein, G. Giruzzi et al., Nucl. Fusion 39, 577 (1999).
• [3] G. Gantenbein, H. Zohm, G. Giruzzi et al., Phys. Rev. Lett. 85, 1242 (2000).
• [4] M. Maraschek, G. Gantenbein, Q. Yu et al., Phys. Rev. Lett. 98, 025005 (2007).
• [5] R.J. La Haye, S. Günter, D.A. Humphreys et al., Phys. Plasmas 9, 2051 (2002).
• [6] C.C. Petty, R.J. La Haye, T.C. Luce et al., Nucl. Fusion 44, 243 (2004).
• [7] R. Prater, R.J. La Haye, T.C. Luce et al., Nucl. Fusion 47, 371 (2007).
• [8] A. Isayama, Y. Kamada, S. Ide et al., Plasma Phys. Control. Fusion 42, L37 (2000).
• [9] A. Isayama, Y. Kamada, N. Hayashi et al., Nucl. Fusion 43, 1272 (2003).
• [10] A. Isayama, N. Oyama, H. Urano et al., Nucl. Fusion 47, 773 (2007).
• [11] A. Isayama, G. Matsunaga, T. Kobayashi et al., Nucl. Fusion 49, 055006 (2009).
• [12] N. Hayashi, A. Isayama, K. Nagasaki et al., J. Plasma Fusion Res. 80, 605 (2004).
• [13] K. Nagasaki, A. Isayama, N. Hayashi et al., Nucl. Fusion 45, 1608 (2005).
• [14] L. Urso, H. Zohm, A. Isayama et al., Nucl. Fusion 50, 025010 (2010).
• [15] F.L. Waelbroeck, Nucl. Fusion 49, 104025 (2009).
• [16] O. Sauter, R.J. La Haye, Z. Chang et al., Phys. Plasmas 4, 1654 (1997).
• [17] A. Gude, S. Günter, S. Sesnic et al., Nucl. Fusion 39, 127 (1999).
• [18] A. Isayama, Y. Kamada, T. Ozeki et al., Nucl. Fusion 41, 761 (2001).
• [19] M. Shimada, D.J. Campbell, V. Mukhovatov et al., Nucl. Fusion 47, S1 (2007).
• [20] A. Isayama, G. Matsunaga, Y. Ishii et al., Plasma Fusion Res. 5, 037 (2010).
• [21] S. Takeji, Y. Kamada, T. Ozeki et al., Phys. Plasmas 4, 4283 (1997).
• [22] T. Kobayashi, M. Terakado, F. Sato et al., Plasma Fusion Res. 4, 037 (2009).

This paper may be cited as follows:

Akihiko ISAYAMA, Go MATSUNAGA, Yoichi HIRANO and the JT-60 Team, Plasma Fusion Res. 8, 1402013 (2013).