Confinement degradation and transport of energetic ions due to Alfvén eigenmodes in JT-60U weak shear plasmas
Confinement degradation and transport of energetic ions due to Alfvén eigenmodes in JT-60U weak shear plasmas
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DOI：
10.1088/0029-5515/47/8/016
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发表时间：
2007-08
期刊：
影响因子：
3.3
通讯作者：
M. Ishikawa;M. Takechi;K. Shinohara;C. Cheng;G. Matsunaga;Y. Kusama;A. Fukuyama;T. Nishitani
中科院分区：
文献类型：
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作者：
M. Ishikawa;M. Takechi;K. Shinohara;C. Cheng;G. Matsunaga;Y. Kusama;A. Fukuyama;T. Nishitani
首次定量地研究了基于负离子的中性束注入对Alfvén本征模（AE）的不稳定性所引起的高能离子的约束退化和输运。在JT-60 U弱剪切等离子体中观察到AE，其频率在几百毫秒的时间尺度上扫描到30-50 kHz，因为等离子体中心的安全系数q（0）从1.75降低到1.5。然后，当q（0）在约600 ms内从1.5减小到1.25时，AE频率饱和，并且AE被识别为TAE。测量的总中子发射率（Sn）在这些AE的存在下进行比较与经典理论预测。其结果是，高能离子的约束退化被确认和Sn的减少率是最大的AE时不稳定的，并位于大的快离子压力梯度区域中的等离子体核心。为了研究高能离子输运由于这些AE，线积分中子发射轮廓测量与大型中子准直器阵列与经典的限制计算进行了比较。结果表明，由于这些AE，高能离子从等离子体核心区域传输到外部区域。此外，电荷交换高能中性粒子通量的能量分布的变化表明，径向高能离子输运是由于高能离子和AE之间的共振相互作用。
The confinement degradation and transport of energetic ions due to Alfvén eigenmodes (AEs) destabilized by negative-ion-based neutral beam injection are quantitatively evaluated for the first time. AEs were observed in JT-60U weak shear plasmas with frequencies sweeping up to 30–50 kHz on a time scale of a few hundred milliseconds as the safety factor at the plasma centre, q(0), decreases from 1.75 to 1.5. Then as q(0) decreases from 1.5 to 1.25 in about 600 ms, the AE frequencies are saturated and the AEs are identified as the TAEs. The measured total neutron emission rate (Sn) in the presence of these AEs is compared with that predicted by classical theory. As a result, the confinement degradation of energetic ions is confirmed and the reduction rate in Sn is largest when AEs are destabilized and are located at the large fast ion pressure gradient region in the plasma core. In order to investigate the energetic ion transport due to these AEs, line-integrated neutron emission profiles measured with a large neutron collimator array are compared with the classical confinement calculations. It is found that energetic ions are transported from the plasma core region to the outer region due to these AEs. Furthermore, changes in the energy distribution of charge exchange energetic neutral particle fluxes suggest that the radial energetic ion transport is due to the resonance interaction between the energetic ions and the AEs.