HT-7超导托卡马克边界等离子体参量及其涨落的实验研究

利用径向可移动朗缪尔三探针和马赫探针对HT-7超导托卡马克边界等离子体参量及其涨落进行了空时空分辨测量.给出了欧姆放电及其与低杂波电流驱动共同作用下边界等离子体电位φ_p、电子温度T_e和电子密度n_e及其涨落的径向分布.实验表明,在限制器附近,存在一由E_r×B确定的极向旋转速度剪切层.在剪切层内,T_e和n_e分布较陡,且φ_p,T_e和n_e的相对涨落水平下降明显.这说明剪切层对边界区的等离子体涨落具有抑制作用.低杂波驱动使径向电场梯度变陡,从而使剪切程度加深但对剪切层宽度无影响.此外,测量表明等离子体环向速度马赫数M_φ存在径向梯度.环向流的这种径向梯度可能是形成径向电场所需的平均极向流的一种重要驱动源 关键词： 托卡马克 边界涨落 低杂波驱动

MEASUREMENT OF EDGE PLASMA PARAMETERS AND THEIR ELECTROSTATIC FLUCTUATIONS ON THE HT-7 SUPERCONDUCTING TOKAMAK

The radial profiles of the electron temperature T_e,the electron density n_e,the plasma potential φ_p,the toroidal Mach number M_p and their electrostatic fluctuations in the plasma boundary region of the HT-7 superconducting tokamak have been measured with a multiarray of Langmuir probes and a set of Mach probes,under the conditions of both ohmic discharge and a lower hybrid current drive.The experimental results show that,under ohmic discharge condition,there is a poloidal velocity shear layer located in the vicinity of the limiter radius,which has a suppression effect on the fluctuations and results in the increase of the radial gradients of T_e and n_e LHCD intensifies the shear.In the same radial position of the poloidal shear layer,there is also a radial shear with the toroidal velocity,which could be the drive source of the mean poloidal flow needed by the formation for radial electric field.