MHD instabilities and magnetic stochasticity driven by the SPARC REMC in 3D nonlinear M3D-C1 simulations R Datta[1], C Clauser[1], G Hu [1,2], N Ferraro [3], R Sweeney [4], R A Tinguely [1] [1] MIT Plasma Science & Fusion Center [2] Wellesley University [3] Princeton Plasma Physics Laboratory [4] Commonwealth Fusion Systems SPARC — a compact, high-current, high-field tokamak designed to achieve a Q > 1 — will test a runaway electron mitigation coil (REMC) for RE suppression during disruptions. This talk will describe the implementation of the SPARC ‘n = 1’ REMC in the extended magnetohydrodynamic (MHD) code M3D-C1. The vacuum magnetic field generated by the REMC is applied as a time-varying magnetic perturbation to the plasma volume. Using this implementation, we investigate the generation of MHD instabilities and magnetic stochasticity in 3D nonlinear MHD simulations. While the REMC reliably stochasticizes outer flux surfaces, flux surfaces near the magnetic axis can be susceptible to rehealing after an initial period of stochasticity. The sensitivity of flux surface reformation to the applied REMC perturbation magnitude and transport coefficients such as the plasma resistivity is explored. Finally, we discuss consequences for RE generation and transport, which is modeled self-consistently in M3D-C1 using a RE fluid model, that comprises Dreicer, tritium beta decay, Compton scattering, and secondary avalanching source terms. This work is supported in part by Commonwealth Fusion Systems and the U.S. DOE.