3D Electromagnetic Physics-Based Modeling to Support Tokamak Design

Three dimensional electromagnetic capabilities have been developed using the new Psi-Tet finite-element model in support of design work for both the SPARC and DIII-D tokamaks. A 3D model of the SPARC tokamak was used to assess the effect of possible non-axisymmetric eddy currents on future SPARC start-up scenarios such as the ability to produce a large null in the poloidal magnetic field. The connection length during the plasma breakdown phase was also assessed using 3D field line tracing as well as studies in the eigenvalue-domain to determine the modification of 3D-effects on the characteristic vertical instability time-scale. A model of the DIII-D device was also created to study the effects of eddy currents on the performance of a passive runaway electron mitigation coil (REMC) currently being developed which is designed to passively drive large non-axisymmetric fields during the plasma. This coil design has been evaluated using electromagnetic analysis, linear MHD modeling, relativistic drift orbit tracing, and 3D finite-element modeling. This presentation will highlight modeling carried out in support of the design which studied the effect of induced eddy currents on the coils ability to apply a strong n=1 radial field at the plasma magnetic axis. It was determined that these currents had a significant effect on the response-time of the coil and similar studies were completed for the SPARC PREMC which is currently under development.