Dynamics of the major disruption of a DIII-D plasma^a)

The dynamics of the major disruption of DIII-D discharge 87009 are investigated with the NIMROD code [Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. To explore the time dynamics in a computationally efficient manner, a fixed-boundary equilibrium is used to model the physics of a plasma being heated through an ideal magnetohydrodynamic (MHD) instability threshold. This simulation shows a faster-than-exponential increase in magnetic energy as predicted by analytic theory [Callen et al., Phys. Plasmas 6, 2963 (1999)]. The dynamics of the heat flux loading on the divertor surfaces is explored with an equilibrium that has the plasma beta raised 8.7% above the best equilibrium reconstruction to start above the ideal MHD threshold. The nonlinear evolution of the ideal mode leads to a stochastic magnetic field and parallel heat transport leads to a localization of the heat flux that is deposited on the wall. The structure of the heat flux deposition is dependent upon the magnetic topology that results from the growth of the ideal mode.