Multi-machine Validation of Plasma Initiation Modelling and Prospects for Future Devices

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

30th IAEA Fusion Energy Conference

Chengdu, China, October 13-18, 2025

Abstract

Multi-machine validation of full electromagnetic plasma initiation modelling with DYON was carried out by the joint modelling of the International Tokamak Physics Activity (ITPA) - Integrating Operating Scenario (IOS) group. The following devices were included in the experiment database: VEST (spherical torus, copper coils, Stainless steel wall, R/a=0.3m/0.2m, Vv=3.7m3), MAST-U (spherical torus, copper coils, C wall, R/a=0.7m/0.5m, Vv=55m3), EAST (conventional tokamak, superconducting coils, metallic wall, R/a=1.85m/0.5m, Vv=38m3), DIII-D (conventional tokamak, copper coils, C wall, R/a=1.67m/0.65m, Vv=35m3), and KSTAR (conventional tokamak, superconducting coils, C wall, R/a=1.8m/0.7m, Vv=55m3). 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 simulation 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 will be 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 ~ 1.5mPa). However, the risk of runaway electron generation must be assessed to confirm the operating space.