Three-dimension spectral characteristics of low-frequency Zonal Flow in the edge plasma of HL-2 A tokamak
Three-dimension spectral characteristics of low-frequency Zonal Flow in the edge plasma of HL-2 A tokamak
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2008
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通讯作者：
A. Liu;T. Lan;H. Zhao;C. Yu;L. Yan;J. Dong;W. Hong;K. Zhao;J. Qian;J. Cheng;D. L. Yu;Q. Yang
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作者：
A. Liu;T. Lan;H. Zhao;C. Yu;L. Yan;J. Dong;W. Hong;K. Zhao;J. Qian;J. Cheng;D. L. Yu;Q. Yang
使用四个朗缪尔探针阵列在 HL-2A 托卡马克等离子体的边缘观察到与大地沉积声学模式 (GAM) 共存的低频层流 (LFZF)。它被识别为低频相干模式，其峰值接近零频率，并且在浮动电势波动的功率谱密度（PSD）上展宽数千赫兹。除了极向轴对称性和环形轴对称性之外，还首先估计了 LFZF 的径向波数频率谱。三维波数-频谱特性为：kθ=kφ≃0，k̄rρi=3.3×10，半峰全宽Δkrρi=0.19，与理论预测和模拟结果基本一致。径向频谱显示 LFZF 封装向外和向内传播，向外净值较小，导致在 LFZF 频率下径向分离的两个探针尖端之间的相移比在 GAM 频率下更小。极向速度涨落的包络线和双谱分析均表明，LFZF与环境湍流（AT）之间的相互作用与GAM与AT之间的相互作用相似，表明其产生机制相同。但不同之处在于，LFZF与AT包络线之间的相干系数比GAM与AT之间的相干系数小，并且包含LFZF的三波相互作用强度也比包含GAM的三波相互作用强度小得多。这些现象可能都是由于边缘区域 LFZF 的小幅度引起的。
The low-frequency Zonal Flow (LFZF), coexisting with the ge od sic acoustic mode (GAM) was observed at the edge of HL-2A tokamak plasmas using four L angmuir probe arrays. It is identified as a low-frequency coherent mode peaking near zero frequenc y and broadening several kilohertz on the power spectral density (PSD) of the floating potential fluctu ations. Besides the poloidal and toroidal axisymmetry, the radial wavenumber-frequency spectra of t he LFZF was firstly estimated. The threedimensional wavenumber-frequency spectral characterist ics: kθ = kφ ≃ 0, k̄rρi = 3.3 × 10 with the full width at half maximum∆krρi = 0.19, are almost consistence with the theoretical predications and simulation results. The radial spectra showing that the LFZF packages propagate both outwards and inwards with a small net value outward, resulting in smaller phase shifts between two probe tips separated radially at the LFZF frequency than the GAM frequency. The en velope and the bispectrum analysis of the poloidal velocity fluctuations both reveal that the inte raction between the LFZF and the ambient turbulence (AT) is as similar as that between the GAM and the A T, suggesting the same generation mechanism. But the differences are: the coherent coefficien ts between the LFZF and the envelope of the AT are smaller than that between the GAM and the AT, and the intensity of the tri-wave interactions including the LFZF is also much smaller than that including t he GAM. These phenomena may both caused by the small amplitude of the LFZF in the edge region.