Multi-machine Validation of Plasma Initiation Modelling and Prospects for Future Devices: Predicting plasma initiation using only hardware design and control room input data

H.-T. Kim, (E. Schuster) et al. (ITPA Integrated Operation Scenario topical group)

Nuclear Fusion 66 (2026) 036043 (12pp)

Abstract

This paper reports on the generic prediction capability of full electromagnetic plasma initiation modelling with DYON, which was carried out for the first time in fusion research by the joint modelling of the International Tokamak Physics Activity—Integrating Operation Scenario group. The following devices were included in the experiment database: VEST (spherical torus, copper coils, Stainless steel wall, R/a = 0.3 m/0.2 m, Vv = 3.7 m3), MAST-U (spherical torus, copper coils, C wall, R/a = 0.7 m/0.5 m, Vv = 55 m3), EAST (conventional tokamak, superconducting coils, metallic wall, R/a = 1.85 m/0.5 m, Vv = 38 m3), DIII-D (conventional tokamak, copper coils, C wall, R/a = 1.67 m/0.65 m, Vv = 35 m3), and KSTAR (conventional tokamak, superconducting coils, C wall, R/a = 1.8 m/0.5 m, Vv = 55 m3). Despite the different hardware features of the devices, the required operating spaces of the loop voltage induction and prefill gas pressure for inductive plasma initiation in each device were successfully reproduced by the predictive simulations with DYON using only the individual hardware design and the control room input data for each discharge. This successful validation across multiple machines demonstrates that the full electromagnetic DYON modelling can capture the essential physics of inductive plasma initiation. The simulation settings commonly employed for all modelling and the modifications necessary to account for the discrepancies between individual devices are reported. Predictions for ITER based on the multi-machine validation indicate that a wide range of prefill gas pressures exists for the Townsend breakdown and the plasma burn-through (0.01–1.5 mPa).