Wall stabilization of a sharp boundary toroidal plasma

The stability of a toroidally symmetric sharp boundary plasma is studied in a wall whose cross section is an arbitrary shape. The wall stabilization has an effect on a fat plasma. The kink mode of the plasma has two stable regions in which toroidal fields and poloidal fields are, respectively, dominant. The second harmonic plays an important role for the stability. For a fixed aspect ratio of the plasma, the stable regions increase accordingly as the plasma shifts outward. If circular walls, elliptical walls, and oval-shaped walls have the same cross-sectional area, the circular wall is the worst case for the stability.