Geometrical improvements of rotational stabilization of high- ballooning modes in tokamaks

Furukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*

We have found numerically that damping phases appear in the time evolution of the perturbation energy of high- ballooning modes in the presence of toroidal shear flows. The damping dominates exponential growth which occurs in the bad curvature region, resulting in stabilization of ballooning modes. D-shaping of plasma cross-section, reduction of aspect ratio, and arrangement of X-point at inner side of the torus enhance the stabilization effect of the toroidal flow through this mechanism.