Description
The X-point radiator (XPR) regime is the subject of a great deal of attention in the magnetic confinement fusion community. It has now been established in most current tokamaks and is a rather attractive potential future reactor scenario, providing both a fully detached divertor and a naturally more ELM-stable regime [1]. Several authors have also successfully demonstrated access to the XPR regime in stand-alone plasma boundary code simulations of both present experiments and for ITER (e.g. [2]). However, for burning plasmas, a critical question is the core-edge compatibility of these XPR regimes. Such assessments require integrated modelling and efforts in this direction are the subject of this contribution.
Our approach is to deploy and, where necessary, further develop the integrated modelling code JINTRAC, currently the workhorse for high-fidelity integrated simulations at the ITER Organization. The 2D nature of the XPR and its localization inside the separatrix require that the domain of EDGE2D Eirene, the plasma boundary solver in JINTRAC, be extended into the confined plasma. We add a new coupling interface between JETTO, SANCO and EDGE2D to accommodate the inwards-shifted boundary location, creating an overlap region between the core and edge models, such that the core transport coefficients can be used in the confined edge while still resolving this zone in 2D. This preserves neoclassical and turbulent transport in the pedestal while using a 2D mean-field code.
We present, to the best of our knowledge, the first ever core-edge integrated modelling simulation of a nitrogen seeded H-mode XPR in ASDEX Upgrade, validating the ELM-stable phase against experiment. We further demonstrate a preliminary exploration of the ITER burning plasma regime under neon-seeded XPR conditions. Here a plethora of transport assumptions and heating schemes is used in the core using boundary conditions obtained with EDGE2D-Eirene. Across the range of parameter scans so far investigated in these early studies, this ITER XPR seems to operate at somewhat reduced fusion gain (Q=3-7) compared the Type-I ELMing H-mode baseline at Q = 10.
[1] M. Bernert et al., Nucl. Mater. and Energy 43 (2025) 101916
[2] A. Poletaeva et al., Nucl. Fusion 64 (2024) 126038