Experimental investigation of m/n = 1/1 and high-order harmonic modes during the sawtooth oscillation in a low β tokamak plasma
Experimental investigation of m/n = 1/1 and high-order harmonic modes during the sawtooth oscillation in a low β tokamak plasma
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DOI：
10.1088/0741-3335/52/1/015008
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发表时间：
2009
影响因子：
2.2
通讯作者：
Changxuan Yu;Xiao-Ye Xu;Jun Wang;Y. Wen;Yi Yu;A. Liu;T. Lan;B. Wan;Xiang Gao;Youwen Sun-You
中科院分区：
文献类型：
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作者：
Changxuan Yu;Xiao-Ye Xu;Jun Wang;Y. Wen;Yi Yu;A. Liu;T. Lan;B. Wan;Xiang Gao;Youwen Sun-You
在HT-7托卡马克上用电子回旋发射成像诊断技术研究了锯齿振荡。高次谐波模式中观察到的超导体前体。它们引起尖锐的压力点，导致在多个地方发生重联事件，并且在低密度时，在q = 1半径的低场侧不是优先的。重连过程分两个阶段进行。在第一阶段，弱重联发生，其特征在于少量热量和粒子通过有限开口缓慢出现。随后，在第二阶段，核心中的大部分剩余热量和粒子向外逃逸。低密度下的观测结果表明，二次重联阶段是由高次谐波模引起的，这在重联模型中很少被提及。然后通过研究大量具有不同密度和qa值的锯齿振荡来描述模式的特性。发现当密度增加到qa = 3.3的阈值以上时，m/n = 1/1模振幅显著超过其谐波。阈值随着qa的增加而减小。
Sawtooth oscillations were investigated using an electron cyclotron emission imaging diagnostic technique on the HT-7 tokamak. High-order harmonic modes are observed in sawtooth precursors. They cause sharp pressure points, leading to the occurrence of reconnection events at more than one place, and which are not preferential on the low field side of the q ∼ 1 radius at low density. The reconnection proceeds in two stages. In the first stage, a weak reconnection happens which is characterized by a slow emergence of a small amount of heat and particles through the finite openings. Subsequently, in the second stage, most of the remaining heat and particles in the core escape outward. The observations at low density indicate that high-order harmonic modes are responsible for the secondary reconnection stage, which has seldom been mentioned in reconnection model. The characteristics of the modes are then described by investigating a large number of sawteeth oscillations with different densities and qa values. It is found that when the density increases above a threshold at qa = 3.3, the m/n = 1/1 mode amplitude significantly exceeds its harmonics. The threshold decreases as qa increases.