Plasma and Fusion Research
Volume 1, 030 (2006)
Rapid Communications
- Japan Atomic Energy Agency
- 1)
- Institute of Advanced Energy, Kyoto University
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
Full Text
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).