Stabilization of External Kink Modes by Means of a Limiter

Abstract

It is shown that poloidal ring limiters are very effective in stabilizing ideal external kink modes in a tokamak. With one poloidal limiter all external modes are stable for $q_a>1\mathrm{}$. However, toroidal limiters have negligible influence on stability. Reversed-field pinches require a finite number of poloidal limiters (typically six) to stabilize the strong external kink modes that would result if the conducting wall were removed.