等离子体中H_α辐射强度涨落的相干结构

Coherent Structures in the H_α Fluctuation in Plasma

采用8道光学纤维成像系统测量了CT-6B托卡马克等离子体中Hα强度的涨落,并使用双正交分解技术(Biorthogonal decomposition method)对涨落信号进行了分析。得到了表征相干结构的权重元素,进一步给出了等离子体湍流中相干结构在时间上的变化和空间上的分布。提取出的主要模式包含了原始信号中相应时刻的大部分相干结构,并从中发现在相邻两道或几道信号中有较强的相干结构,表明此相干结构在空间上局部地存在于等离子体湍流中。结果对托卡马克等离子体研究具有重要意义。

The Hα fluctuation emitting from the CT-6B Tokamak plasma was measured by an eight-channel optical fibers set-up, and the fluctuation data were analyzed by the biorthogonal decomposition method (BD). The distribution of the biorthogonal weights An, by which coherent structures in plasma turbulence can be indicated, was obtained. The detailed information on the time evolution and spatial distribution of the coherent structures is reported. The analysis of the dominant mode extracted by the BD shows that the temporal-component curve was composed of most coherent structures existing in the original signals. Moreover, we found that there was strong coherence among signals from two or more adjacent channels, which indicated that the coherent structures locally exist in plasma turbulence. The result is of importance to Tokamak plasma study.