Speaker
Description
The X-point radiator (XPR) regime (see the Ref. [1] and the references therein) is now commonly explored in most modern tokamaks using a variety of impurity seeding gases. Given its usual association with almost complete divertor detachment and benign or no ELM activity, it is an extremely attractive potential option for future reactor-scale machines.
On the SOLPS-ITER numerical simulation side, steady-state modelling has successfully reproduced the experimental XPR regime in ASDEX-Upgrade [2] and has been used to achieve the first predictive modelling of this regime for ITER [3]. One caveat is that maintaining a stable XPR regime in these simulations requires boundary conditions with fixed densities and temperatures at the inner core boundary and a high concentration of radiating impurity.
An alternative modelling strategy to achieve and stabilize the XPR regime has recently been demonstrated in [4] for ASDEX Upgrade based on SOLPS-ITER dynamic modelling. This approach uses feedback control of the XPR regime by varying the impurity seeding in a similar fashion to the experimental methods of XPR control and stabilization. The chosen control parameter for feedback is the minimum electron temperature at a selected core flux surface where the radiating region is located. In contrast to the previous stationary simulations, in this new dynamic modelling, more physically justified boundary conditions of fixed heat and particle flows from the core are applied at the inner core boundary.
We present here the first dynamic SOLPS-ITER simulations of the XPR regime in ITER following the strategy developed in [4]. Calculations are performed for neon and argon as radiating impurities. The dynamics of the transition to the XPR regime and the possibility of achieving a steady-state XPR solution in ITER is investigated. The resulting stable X-point radiator regimes are achieved with lower impurity content and power crossing the inner core boundary than in [3]. As a result, the XPR is obtained with relatively low Zeff in the core region of the simulation domain which is favourable for integration of the regime with burning plasma operation.
[1] Bernert M. et al 2025 Nucl. Mater. Energy 43, 101916
[2] I.Senichenkov et al. 2021 Plasma Phys. Control. Fusion 63 055011
[3] A. Poletaeva et al 2024 Nucl. Fusion 64 126038
[4] A. Poletaeva et al 2025 CPP to be published