Geometrical Improvements of Rotational Stabilization of High-n Ballooning Modes in Tokamaks
M. Furukawa1), S. Tokuda1), and M. Wakatani2)
1) Naka Fusion Research Establishment, JAERI, Naka, Ibaraki 311-0193, Japan
2) Graduate School of Energy Science, Kyoto University, Gokasho, Uji 611-0011, Japan
Abstract.
We have found numerically that damping phases appear in the time evolution of the perturba-tion energy of high-n 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 e ect of the toroidal flow through this mechanism.