Error-Field and Resistive Wall Coupling in NIMROD

Boundary conditions for a periodic cylinder that allow for the simultaneous presence of a resistive wall and external error fields have been successfully implemented in \textsc{nimrod}. Small magnetic field errors stemming from coil feeds and misalignment are present in all devices. These errors are modeled as small helical currents at some radius outside the resistive wall, which contribute terms to the \textsc{nimrod} boundary condition at the wall. Using these new \textsc{nimrod} capabilities, error-field penetration is studied for intrinsically stable rotating plasmas. An axial equilibrium flow is included in the simulation in order to observe suppression of error-field driven modes by rotation. Error-fields of a critical amplitude penetrate the plasma and create stationary magnetic islands. These numerical results are compared to the analytic predictions of Fitzpatrick [Nucl. Fusion \textbf{33}, 1049 (1993)] for periodic cylinder geometry and visco-resistive plasmas. Further generalization of the resistive wall and error-field boundary conditions in \textsc{nimrod} to toroidal geometry will be discussed.