Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D
Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D
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DOI：
10.1063/1.3575159
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发表时间：
2011-05
影响因子：
2.2
通讯作者：
M. Okabayashi;G. Matsunaga;J. Degrassie;W. Heidbrink;Y. In;Yueqiang Liu;H. Reimerdes;W. Solomon
中科院分区：
文献类型：
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作者：
M. Okabayashi;G. Matsunaga;J. Degrassie;W. Heidbrink;Y. In;Yueqiang Liu;H. Reimerdes;W. Solomon
能量粒子（EP）驱动的离轴鱼骨状模（OFM）经常触发JT-60 U和DIII-D器件中的电阻壁模（RWM），从而阻止长时间高βN放电。在这些实验中，EP是由中性束注入的高能离子（70-85 keV），以产生高压等离子体。EP驱动的爆发事件同时降低EP密度和等离子体旋转。这些变化在高βN低旋转等离子体中是显著的，其中RWM稳定性被预测强烈地受到EP进动漂移共振和q = 2表面附近的等离子体旋转（动力学效应）的影响。使用MARS-K代码的自洽扰动的模式结构的稳定性的这些影响的分析表明，EP损失和旋转下降的影响是足够的不稳定的RWM在低旋转等离子体，当等离子体旋转归一化的阿尔芬频率只有百分之零点几附近的q = 2的表面。JT-60 U和DIII-D的OFM特性非常相似，包括非线性模式演化。模式的增长最初像一个经典的鱼骨，然后模式结构变得强烈扭曲。OFM对外加n = 1外场的动态响应表明，该模式保留了其外部扭结特征。这些比较研究表明，高能粒子驱动的离轴鱼骨状模式是壁稳等离子体中外部扭结模式的一个新的EP驱动分支，类似于经典鱼骨分支与内部扭结模式的关系。© 2011美国物理研究所。
An energetic-particle (EP)-driven off-axis-fishbone-like mode (OFM) often triggers a resistive wall mode (RWM) in JT-60U and DIII-D devices, preventing long-duration high-βN discharges. In these experiments, the EPs are energetic ions (70-85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce the EP density and the plasma rotation simultaneously. These changes are significant in high-βN low-rotation plasmas, where the RWM stability is predicted to be strongly influenced by the EP precession drift resonance and by the plasma rotation near the q = 2 surface (kinetic effects). Analysis of these effects on stability with a self-consistent perturbation to the mode structure using the MARS-K code showed that the impact of EP losses and rotation drop is sufficient to destabilize the RWM in low-rotation plasmas, when the plasma rotation normalized by Alfven frequency is only a few tenths of a percent near the q = 2 surface. The OFM characteristics are very similar in JT-60U and DIII-D, including nonlinear mode evolution. The modes grow initially like a classical fishbone, and then the mode structure becomes strongly distorted. The dynamic response of the OFM to an applied n = 1 external field indicates that the mode retains its external kink character. These comparative studies suggest that an energetic particle-driven off-axis-fishbone-like mode is a new EP-driven branch of the external kink mode in wall-stabilized plasmas, analogous to the relationship of the classical fishbone branch to the internal kink mode. © 2011 American Institute of Physics.