NIMROD simulations in support of Disruption Event Characterization and Forecasting (DECAF)*

As unmitigated disruptions for next-generation, higher-performance plasma devices such as ITER [1] are anticipated to produce unacceptable forces on the device and unacceptable heat loads on the plasma facing components, the need for accurate and timely disruption avoidance and mitigation systems is vital in future devices. Effective disruption avoidance and mitigation relies crucially on an ability to predict, in real-time, the plasma state, and as necessary, to activate appropriate actuators to keep the plasma away from disruption boundaries in parameter space. The Disruption Event Characterization and Forecasting (DECAF) code [2] automates the identification of the chain of events leading to a disruption and provides appropriate forecasting of such events, allowing appropriate plasma control systems to be activated to prevent (or mitigate) plasma disruptions. Recent work on the KSTAR tokamak demonstrated a 100% real-time forecasting accuracy using DECAF [3]. To support disruption characterization and forecasting work in DECAF, NIMROD simulations are performed to assess the physical characteristics of disruption relevant scenarios in MAST-U and KSTAR plasmas. In particular, the physics of fast reconnection events, double tearing modes, island overlap and mode coupling, and stochasticity are investigated. The understanding gained from these calculations will enable the development of reduced models to be incorporated into DECAF.

[1] A. H. Boozer, “Plasma steering to avoid disruptions in ITER and tokamak power plants”, Nuclear Fusion 61, 054004 (2021).

[2] S. A. Sabbagh, et al., “Disruption event characterization and forecasting in tokamaks”, Phys. Plasmas 30, 032506 (2023).

[3] Sabbagh, Y. S. Park, J. D. Riquezes, et al., 2023 Proceedings of the 29th IAEA Fusion Energy Conference, London, United Kingdom (International Atomic Energy Agency, Vienna, 2023) Paper IAEA-CN-316/2038