[Table of Contents]

Plasma and Fusion Research

Volume 1, 030 (2006)

Rapid Communications

Control of Growth of Neoclassical Tearing Mode by Central Co-ECCD in JT-60U
Akihiko ISAYAMA, Naoyuki OYAMA, Hajime URANO, Takahiro SUZUKI, Manabu TAKECHI, Shunsuke IDE, Yutaka KAMADA, Takahisa OZEKI, Kazunobu NAGASAKI1) and the JT-60 Team
Japan Atomic Energy Agency
1)
Institute of Advanced Energy, Kyoto University
(Received 15 April 2006 / Accepted 25 April 2006 / Published 5 June 2006)

Abstract

Growth of a neoclassical tearing mode (NTM) with a poloidal mode number m = 3 and a toroidal mode number n = 2 has been controlled by electron cyclotron current drive (ECCD) in the same direction as the plasma current (co-ECCD) in the central region away from the NTM island. By using ECCD at a fraction of about 10% of the plasma current, the amplitude of the m/n = 3/2 NTM is limited to about 1/5 of that without ECCD. The frequency spectrum of magnetic perturbations shows that the frequency of the m/n = 3/2 NTM is modulated by a sawtooth crash. The beta value, which is the ratio of the plasma pressure to the magnetic pressure, is higher by 6% than that without ECCD at the same input power. This operational scenario is quite different from that for conventional NTM stabilization in which the ECCD location is accurately adjusted at the mode rational surface and is thus off-axis. This result shows the compatibility of sawtooth oscillations and a small-amplitude 3/2 NTM, and suggests the possibility of a new and easier operational scenario for NTM control.

Keywords

neoclassical tearing mode, sawtooth oscillation, electron cyclotron current drive, plasma instability, JT-60U

DOI: 10.1585/pfr.1.030

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References

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This paper may be cited as follows:

Akihiko ISAYAMA, Naoyuki OYAMA, Hajime URANO, Takahiro SUZUKI, Manabu TAKECHI, Shunsuke IDE, Yutaka KAMADA, Takahisa OZEKI, Kazunobu NAGASAKI and the JT-60 Team, Plasma Fusion Res. 1, 030 (2006).