HT-7超导托卡马克边缘涨落谱特征及湍流输运研究

ELECTROSTATIC FLUCTUATIONS AND TURBULENT TRANSPORT STUDIES IN THE HT-7 SUPERCONDUCTING TOKAMAK EDGE PLASMAS 

用郎缪尔三探针对HT 7超导托卡马克边缘等离子体涨落进行了高时空分辩测量 .给出了欧姆放电下涨落幅度的径向分布、谱特征及传播特性 .实验观察表明 ,在由Er×B确定的极向旋转速度剪切层附近 ,等离子体电位、电子温度和电子密度的相对涨落水平和两两间的相干系数均有明显下降 ,其极向互相关函数亦减小 ,这说明剪切层对涨落具有去相关作用 .由涨落驱动的径向局域粒子输运通量Γtur测量显示出湍动输运具有时间上的阵发特性。将悬浮电位涨落～f2 的自动率谱P～f～f 和局域粒子输运通量的频谱Γtur(f)对比可见 ,Γtur(f)的峰值位置均落在P～f～f 的 1 f频段 。

Electrostatic fluctuations and turbulence-induced particle flux have been investigated in the plasma boundary region of the HT-7 superconducting tokamak. There is a poloidal velocity shear layer driven by E-r x B-T located in the vicinity of the limiter radius, which has a suppression effect on the fluctuations and results in reductions in the normalized fluctuation level, coherence between the two plasma parameter fluctuations of <(<phi>)over tilde>(p) (T) over tilde (e) and (n) over tilde (e). The radial decorrelation effect of the poloidal velocity shear causes a decrease in the turbulent flux. The time evolution of the turbulent flux shows bursts in turbulent transport. The frequency range where the turbulent flux, which comes in bursts, is dominant has been identified. It is in this frequency range that the spectral region with power decay close to 1/f of the power spectrum of the floating voltage fluctuation has been found. This result could be a signature of the turbulent transport close to instability threholds.