Multi-tokamak Application of a VDE Forecasting Approach for Disruption Avoidance using DECAF*

The ability to forecast vertical displacement events (VDEs) for the purposes of disruption avoidance and mitigation will be a crucial feature of any future tokamak-based fusion power plant. A study of the accuracies of common vertical stability metrics, including the vertical instability growth rate and a vertical force balance, applied to datasets consisting of full shot-years from the MAST-U, KSTAR, and NSTX tokamaks has resulted in the development of a VDE forecasting approach that advances disruption warning time on average by over a factor of three and can facilitate avoidance of the ideally vertically uncontrollable regime altogether. DECAF was used for the development and validation of this model [1]. The applicability of this approach in real-time is enabled by a linear forward model that produces two-dimensional toroidal current density profiles from external magnetic field measurements with high accuracy (R² of 0.992 compared to using full equilibrium reconstructions alone). Work is underway to employ this model in the real-time plasma control system on KSTAR. This study and the performance of a resulting ‘time to disruption’ estimator indicate this approach is an attractive strategy for implementation on future tokamak reactors as a means of minimizing the risk of VDE-induced disruptions.