Kink Instabilities in a Tokamak of Large βp

Kink instabilities in high β regime of tokamak, i.e. β p ∼ε 1/2 and q ( a )∼1, are studied in toroidal geometry, where ε is an inverse aspect ratio and q ( a ) is a safty factor at a plasma surface r = a . The n =1 kink mode becomes unstable for q ( a ) above Kruskal Shafranov limit. At marginal stability, the amplitude of m =2 mode becomes larger than that of m =1 mode for larger b / a , where b is a position of conducting shell. The stabilizing effect of conducting shell on the n =1 kink mode can be expected for b / a <1.4.