Verification of role of neoclassical poloidal viscosity on transition to improved confinement mode in toroidal plasma

在大型螺旋装置(LHD)和氦-J加速器上进行了不同磁配置下的电极偏置实验，从理论和实验两个方面对新古典主义极向粘度进行了估算。特别是在LHD中，用Fortec-3D程序计算了考虑有限拉莫半径效应的新经典极向粘性。该模拟使我们能够高精度地计算新古典主义的极向粘度。LHD和Heliotron J的实验粘度和理论粘度都与以前在TU-Heliac和CHS中估算的粘度进行了比较。结果表明，实验结果与理论预测吻合较好。除了这些结果外，我们还意外地在氦J的边缘偏置条件下观察到了爆发式跃迁，这是一个新的有趣的物理现象。

The electrode biasing experiments were carried out in various magnetic configurations in the Large Helical Device (LHD) and the Heliotron J. The neoclassical poloidal viscosity was evaluated from the theory and the experiments. Especially in the LHD, the neoclassical poloidal viscosity was calculated using FORTEC-3D code, which includes the finite Larmor radius effect. The simulation enabled us to calculate the neoclassical poloidal viscosity with high accuracy. Both the experimental and theoretical viscosities obtained in the LHD and the Heliotron J were compared with those previously evaluated in TU-Heliac and the CHS. Consequently the experimental results show good agreement with the theoretical prediction. In addition to those results, we unexpectedly observed the burst like transition under the marginal biasing condition in the Heliotron J, which is new interesting physical phenomenon.