Simplified multimode calculations of resistive wall modes

Feedback stabilization of kink instabilities that would be stable if the conducting structures around the plasma were perfectly conducting is important for achieving sufficient plasma pressure in tokamak fusion systems. The natural growth rate of these instabilities, which are called resistive wall modes (RWMs), is proportional to the resistivity of the surrounding conductive structures. The development of perturbed equilibrium codes allows a simplified treatment of the plasma response and of the separation of the description of the plasma response from that of the external conducting structures. This simplified treatment is given for the case in which an arbitrary number of modes of the plasma response are retained.