Coupling ThinCurr and GPEC to Assess the Stability Implications of Induced Currents in Fusion Devices

Understanding the interaction between plasma currents and eddy currents driven in device-specific structures is crucial for predicting plasma stability and confinement. We present a new workflow that couples ThinCurr—a thin-wall electromagnetic modeling code—and the Generalized Perturbed Equilibrium Code (GPEC), which can calculate the resonant coupling between external perturbations and toroidal plasmas. Time-dependent field perturbations of vacuum vessel eddy currents and current filaments for coils and plasma are computed on a GPEC-defined control surface. One-dimensional and two-dimensional Fourier analysis is performed on the calculated field, which can be input to GPEC for calculating the plasma response. This integrated computational approach adds field perturbation Fourier analysis capabilities to ThinCurr and offers a streamlined coupling to GPEC, facilitating the study of equilibrium device responses to error fields. The workflow will be exploited to analyze the effects of wall eddy currents and induced currents in closed-circuit Runaway Electron Mitigation Coils (REMC) during plasma current quench and start-up.

Work supported by US DOE under DE-SC0024898, DE-SC0021968, and by Columbia University