The M3D-C1 Code as a Tool for Design Validation and Whole-Facility Modeling

Recent developments in the M3D-C1 code extend its use for tokamak and stellarator design validation. M3D-C1 is a parallel, implicit, finite element code that provides the capability to simulate MHD equilibrium and stability by combining a 3D, nonlinear fluid plasma model with a variety of models for sources, impurities, transport, and external conductors. A new meshing capability enables the efficient treatment of multiple conducting regions, such as the nested vessels in ITER and SPARC. These regions allow anisotropic, nonaxisymmetric resistivity, and spatially-resolved eddy and halo currents. Utilizing an impurity radiation and transport model, simulations of disruption mitigation in NSTX-U, DIII-D, ITER, KSTAR, and SPARC yield detailed predictions of thermal and electromechanical loads. Furthermore, a fluid model for runaway electrons allows self-consistent evolution of runaway electrons and nonlinear MHD stability. A capability to use nonaxisymmetric spatial domains enables simulations of strongly-shaped stellarators, including W7-X and LHD, and to self-consistently describe the breakup of magnetic surfaces and the nonlinear evolution of the pressure profile. Finally, M3D-C1 has been used to map non-ideal peeling-ballooning stability thresholds, which may differ strongly from ideal thresholds in NSTX. Taken together, these capabilities provide a unique new tool for high-fidelity design validation and whole-facility modeling.