Free-boundary simulations of DIII-D plasmas with the NIMROD code Original Research Article

Modeling long-wavelength instabilities in modern tokamak discharges provides many numerical challenges due to the extreme temporal and spatial stiffness as the plasma becomes nearly collisionless. To meet these numerical challenges, the NIMROD code uses a high-order finite-element representation for the poloidal plane, and a pseudo-spectral method for the toroidal direction. The spectral convergence of the high-order elements is important for resolving anisotropic heat conduction at realistic parameters. Simulation results of a tokamak disruption which requires anisotropic heat conduction show that most of the heat flux is concentrated in the divertor region, but not where the initial strike points are located.