UEDGE modeling of plasma detachment of CFETR with ITER-like divertor geometry by external impurity seeding

Abstract

Efficient handling of high heat flux on the plasma-facing components, particularly the divertor targets, poses a significant challenge for the Chinese Fusion Engineering Testing Reactor (CFETR) with fusion power of Gigawatt. This work investigates the divertor plasma detachment of CFETR with a standard ITER-like divertor geometry by neon (Ne) or argon (Ar) impurity seeding using UEDGE code. The cross-field drifts terms are switched off, and fluid neutral models and a “fixed-fraction” impurity model are applied to enable efficient simulations for the study of CFETR detachment. In order to reduce the heat load on the divertor targets below the acceptable level (<10 MW/m²), the impurity fraction (f), pumping speed (S), and upstream density are varied to identify the suitable operations window during Ne seeding. The effects of Ne and Ar impurities on the plasma detachment are compared. It is found that with the power across the core-edge interface P_SOL = 200 MW and separatrix density of 2.8 $\times$ 10¹⁹ $m^{-3}$, Ne impurity fraction ≥1.7%, and Ar impurity fraction ≥0.24% can achieve the partial detachment. Achieving similar total radiation power (˜148 MW), the Ne fraction is 2.3% and the Ar fraction is 0.24%. Moreover, the simulation results indicate that Ar exhibits better power radiation efficiency and core compatibility compared with Ne.