Stabilization of line tied resistive wall kink modes with rotating walls

A method suggested by Gimblett [ C. G. Gimblett, Plasma Phys. Controlled Fusion, 31 2183 (1989) ] for stabilizing resistive wall modes by using a rotating double wall configuration is applied to a line tied screw pinch equilibrium. The line tied boundary conditions provide an additional stabilizing mechanism relative to instabilities present in periodic cylinders that limits ideal kink instability to only be present when qa<1 for m=1 modes. With differentially rotating walls, resistive wall modes can be stabilized with qa values less than unity. For a given equilibrium, there exists an optimal spacing between a stationary and a rotating wall that minimizes the critical wall rotation frequency for stabilization.