DISCHARGE IMPROVEMENT THROUGH CONTROL OF NEOCLASSICAL TEARING MODES BY LOCALIZED ECCD IN DIII-D
DISCHARGE IMPROVEMENT THROUGH CONTROL OF NEOCLASSICAL TEARING MODES BY LOCALIZED ECCD IN DIII-D
复制标题
DOI：
10.1088/0029-5515/43/10/014
复制
发表时间：
2002-10
期刊：
影响因子：
--
通讯作者：
R. Prater;R. Lahaye;J. Lohr;T. Luce;C. Petty;Ferrón;D. Humphreys;E. Strait;F. Perkins;R. Harvey
中科院分区：
文献类型：
--
作者：
R. Prater;R. Lahaye;J. Lohr;T. Luce;C. Petty;Ferrón;D. Humphreys;E. Strait;F. Perkins;R. Harvey
A271通过DIII-D中局部ECCD控制新古典撕裂模式改善放电。新古典撕裂模（NTM）是一种MHD模，它可以限制托卡马克中高β放电的性能，在某些情况下会导致重大破坏。导致NTM生长的不稳定效应是由种子磁岛局部减小等离子体压力梯度引起的自举电流的螺旋形减小。NTM特别适合于控制，因为模式是线性稳定的，尽管非线性不稳定，所以如果岛幅度可以降低到阈值大小以下，则模式将衰减并消失。缩小岛的一种方法是用电子回旋电流驱动（ECCD）产生的局部电流替换缺失的自举电流。这种方法已被应用到m=3/n=2的新古典撕裂模式在DIII-D，在H模式等离子体与正在进行的ELMs和锯齿，这两个周期性地产生种子岛。在3/2模式的情况下，通过在非常接近模式的有理表面处施加约1.5 MW的ECCD，获得了鲁棒的完全抑制。当模式第一次出现在等离子体中时，存储的能量减少20%，但是在模式被ECCD稳定之后，通过额外的中性束加热，β可以被提高到初始阈值压力以上20%，从而产生接近因子2的极限β的改善。实施了一种创新的自动搜索算法，以在存在该模式的情况下找到并保留幼儿保育和发展的最佳位置。
A271 DISCHARGE IMPROVEMENT THROUGH CONTROL OF NEOCLASSICAL TEARING MODES BY LOCALIZED ECCD IN DIII-D. Neoclassical tearing modes (NTMs) are MHD modes which can limit the performance of high beta discharges in tokamaks, in some cases leading to a major disruption. The destabilizing effect which results in NTM growth is a helical decrease in the bootstrap current caused by a local reduction of the plasma pressure gradient by seed magnetic islands. The NTM is particularly well suited to control since the mode is linearly stable although nonlinearly unstable, so if the island amplitude can be decreased below a threshold size the mode will decay and vanish. One means of shrinking the island is the replacement of the missing bootstrap current by a localized current generated by electron cyclotron current drive (ECCD). This method has been applied to the m=3/n=2 neoclassical tearing mode in DIII-D, in H-mode plasmas with ongoing ELMs and sawteeth, both of which generate seed islands periodically. In the case of the 3/2 mode, full suppression was obtained robustly by applying about 1.5 MW of ECCD very near the rational surface of the mode. When the mode first appears in the plasma the stored energy decreases by 20%, but after the mode is stabilized by the ECCD the beta may be raised above the initial threshold pressure by 20% by additional neutral beam heating, thereby generating an improvement in the limiting beta of nearly a factor 2. An innovative automated search algorithm was implemented to find and retain the optimum location for the ECCD in the presence of the mode.