Influence of wall thickness on the stability of the resistive wall mode in tokamak plasmas

The influence of finite wall thickness on the stability of the resistive wall mode (RWM) in a tokamak is determined using a simple cylindrical plasma model in which the dissipation required to stabilize the mode is provided by neoclassical parallel ion viscosity. For present-day tokamaks, which possess relatively thin walls, finite wall thickness effects are found to have relatively little influence on the RWM stability boundaries, which are almost the same as those calculated in the thin-wall limit. On the other hand, for next-step devices, which are likely to possess much thicker walls than present-day tokamaks, finite wall thickness effects are found to significantly impede the ability of plasma rotation to stabilize the RWM all the way to the perfect-wall stability limit.