Optimization of Radial Electric Field in Toroidal Plasmas

为了提高环形器件的高温等离子体约束效率，研究表明，E*B漂移产生的径向电场或极向剪切流是有效的。禁闭改善的L-H相变可能是由边缘区域的径向电场分叉触发的。对于径向电场约束的改进，我们得到了以下结果：(1)交换模与极向剪切流之间的相互作用是L-H相变的根源。基于这种相互作用，还可以对在H模过程中观察到的ELM(边缘局域模)进行建模。(2)为了研究在某些特定装置中是否可能发生L-H跃迁，我们评估了用来确定托卡马克和星耀器中极向速度的非线性粘性。(3)当极向流的速度切变较大时，一个负面影响是Kelvin-Helmholtz(K-H)不稳定性的激发。给出了激发K-H不稳定性的条件及其非线性行为。

For improving the efficiency of high temperature plasma confinement in toroidal devices, it has been shown that the radial electric field or the poloidal shear flow generated by the E * B drift is effective. The L-H transition for confinement improvement may be triggered by the bifurcation of radial electric field in the edge region. We have obtained the following results for the improvement of confinement with the radial electric field.(1) The interaction between the interchange mode and the poloidal shear flow is considered as the origin of the L-H transition. The modeling of ELM (Edge Localized Mode) observed during the H mode is also possible based on this interaction.(2) Nonlinear viscosity to determine the poloidal velocity in tokamaks and stellarators is evaluated for studying whether the L-H transition is possible or not in some specific devices. A strategy to obtain the H mode in a stellarator is discussed.(3) When the velocity shear of poloidal flow becomes large, one negative effect is the excitation of Kelvin-Helmholtz (K-H) instability. The condition for exciting the K-H instability and its nonlinear behavior have been shown for the heliotron device.