NIMROD simulations of disruption-relevant phenomena in support of Disruption Event Characterization and Forecasting (DECAF)

Disruption prediction and avoidance are paramount issues for next generation tokamaks aiming to produce net fusion power. These machines cannot handle the high heat loads and large forces that would be produced in unmitigated disruptions. Such disruptions should at the very least be mitigated, but even better is to avoid disruptions altogether. This is the aim of DECAF. DECAF has already produced its first real time disruption avoidance on the KSTAR tokamak [1], and future experiments are forthcoming. To support DECAF, NIMROD simulations are performed to simulate disruption and stability phenomena in tokamaks. The goal of these simulations is to provide further understanding of the underlying physics, ultimately leading to disruption avoidance solutions for present and future tokamak devices. Among the phenomena that are currently being investigated (or are planned to be investigated) in NIMROD include: the effects and prevalence of resistive wall tearing modes (RWTM) and their relationship to disruptions, mechanisms to achieve and sustain high beta in spherical tokamaks, mechanism of fast thermal quenches and their relationship to disruptions, and mode activity and mode coupling leading to disruptions. Initial NIMROD analysis of RWTMs has already been undertaken, and preliminary results shows the required mode coupling to device electrical conducting structure. [1] https://www.apam.columbia.edu/first-demonstration-tokamak-disruption-avoidance-disruption-event-characterization-and-forecasting-0