Dynamic Formation of Plasma Rotation in a Tokamak

本文研究了(1)等离子体旋转的动态形成过程，(2)等离子体旋转与剪切电子结构的关系，(3)旋转螺旋磁场对等离子体旋转的形成过程。到目前为止，在HYBTOK-II托卡马克装置上安装了焦耳和垂直场线圈的快速响应IGBT电源，以产生具有良好重复性的靶托卡马克等离子体。通过数字信号处理器对等离子体水平位置的数字反馈控制，可以非常有效地实现等离子体电流的灵活操作，如交流托卡马克操作、电流快速上升等。在HYBTOK-II上安装了以m=6/n=1为主要模式的螺旋线圈，并研究了该螺旋线圈系统中感应旋转螺旋场的特性。当螺旋场旋转方向与等离子体E×B旋转方向相同时，由于岛的形成使等离子体电流重新分布，相对速度减小，RHF强度增强。当它们相反时，在谐振层产生的屏蔽电流显著地抑制了RHF的强度。电极偏置被用来调节等离子体的旋转。在初步实验中，发现电极偏置对等离子体旋转的修正对RHF的穿透有很大的影响，并且在偏置后RHF强度出现了动态驰豫。

This research has been carried out to study (1) the dynamic formation process of the plasma rotation, (2) the relation between the plasma rotation and the sheared electric structure and (3) the formation process of the plasma rotation by the rotating helical magnetic field. So far, the following results has been obtained ;Fast response IGBT power supplies for Joule and vertical field coils have been installed in HYBTOK-II tokamak in order to produce target tokamak plasmas with good reproducibility. By the digital feedback control of the plasma horizontal position with a digital signal processor, flexible operation of the plasma current can be done very effectively, such as AC tokamak operation, rapid current rise and so on.Helical coils with m=6/n=1 as a main mode has been installed in HYBTOK-II and characteristics of the induced rotating helical field(RHF) in the present helical coil system were studied. When the direction of the helical field rotation is same as that of the plasma E × B rotation, the relative velocity decreases and the intensity of RHF is enhanced due to redistribution of the plasma current by island formation. When they are opposite, the intensity of RHF is remarkably dumped by the generation of the shielding current at the resonance layer.The electrode biasing is applied to modify the plasma rotation. In the preliminary experiment it is found that the modification of the plasma rotation by electrode biasing strongly affects the penetration of RHF and the dynamic relaxation of the RHF intensity has been observed just after the turn of the biasing.