Stabilization of neoclassical tearing mode by ECCD and its evolution simulation on JT-60U tokamak

被引:38
作者
Nagasaki, K [1 ]
Isayama, A
Hayashi, N
Ozeki, T
Takechi, M
Oyama, N
Ide, S
Yamamoto, S
机构
[1] Kyoto Univ, Inst Adv Energy, Uji, Kyoto 6110011, Japan
[2] Japan Atom Energy Res Inst, Naka, Ibaraki 3110193, Japan
关键词
D O I
10.1088/0029-5515/45/12/016
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
Stabilization of an m = 3/n = 2 neoclassical tearing mode (NTM) by a local electron cyclotron current drive (ECCD) has been studied in high beta(p) ELMy H-mode plasmas in the JT-60U tokamak. In the stabilization experiment, the electron cyclotron (EC) injection timing is scanned from the 'before mode onset' phase (preemptive ECCD) to the mode saturation phase (late ECCD). It has been demonstrated that the ECCD is more effective when it is applied before the mode onset and the critical timing for effective ECCD is related to the mode excitation phase. The EC power to prevent the 3/2 NTM excitation by preemptive ECCD is lower by about 20% compared with complete stabilization by late ECCD. Even when the 3/2 NTM is excited, the stabilization effect is stronger than for late ECCD. For a high performance plasma of the normalized beta, beta(N) = 3.0, the H-factor H-89PL improves from 1.9 to 2.1 when the 3/2 NTM is suppressed. A numerical study has been made based on the modified Rutherford equation coupled with a 1.5D transport code and an EC code. The simulation reproduces well the time evolution of the magnetic island both at the growing and stabilizing phases. The simulation results show that it is important to adjust not only the EC current position but also its width to stabilize the NTM effectively. The reduction of EC power for NTM prevention in experiments for preemptive ECCD can be explained by the increase of the minimum seed island size for NTM excitation.
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页码:1608 / 1617
页数:10
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