Stabilization of neoclassical tearing mode by ECCD and its evolution simulation on JT-60U tokamak
Stabilization of neoclassical tearing mode by ECCD and its evolution simulation on JT-60U tokamak
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DOI：
10.1088/0029-5515/45/12/016
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发表时间：
2005-11
期刊：
影响因子：
3.3
通讯作者：
K. Nagasaki;A. Isayama;N. Hayashi;T. Ozeki;M. Takechi;N. Oyama;S. Ide;S. Yamamoto
中科院分区：
文献类型：
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作者：
K. Nagasaki;A. Isayama;N. Hayashi;T. Ozeki;M. Takechi;N. Oyama;S. Ide;S. Yamamoto
在JT-60U托卡马克高β p ELMy H模等离子体中，研究了局域电子回旋电流驱动（ECCD）对m = 3/n = 2新经典撕裂模（NTM）的稳定作用。在稳定实验中，电子回旋（EC）注入定时扫描从“前模式开始”阶段（抢先ECCD）的模式饱和阶段（晚ECCD）。已经证明，ECCD是更有效的，当它被施加之前的模式启动和有效的ECCD的关键时刻有关的模式激发阶段。与晚期ECCD完全稳定相比，抢先ECCD阻止3/2 NTM激发的EC功率降低约20%。即使当3/2 NTM被激发时，稳定效果也比晚期ECCD更强。对于归一化β（β N = 3.0）的高性能等离子体，当3/2 NTM被抑制时，H因子H89PL从1.9提高到2.1。基于修正的卢瑟福方程，结合1.5维输运程序和EC程序，进行了数值研究。模拟结果很好地再现了磁岛在生长和稳定阶段的时间演化。仿真结果表明，不仅要调整EC电流的位置，而且要调整其宽度，才能有效地稳定NTM。NTM预防的EC功率在实验中的抢先ECCD的减少可以解释为NTM激发的最小种子岛尺寸的增加。
Stabilization of an m = 3/n = 2 neoclassical tearing mode (NTM) by a local electron cyclotron current drive (ECCD) has been studied in high βp 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, βN = 3.0, the H-factor H89PL 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.