Divertor power exhaust with Ar impurity seeding for CFEDR H-mode operation

A conventional single-null divertor geometry has been proposed for the China Fusion Engineering Demo Reactor (CFEDR). The divertor performance of CFEDR under the conventional high confinement mode (H-mode) scenario with a fusion power of 1.5 GW has been evaluated using the SOLPS-ITER code package. A comparative simulation has been carried out with two different gas puffing settings. The results indicate that simultaneous seeding with both argon (Ar) and deuterium (D) presents a promising solution to divertor power exhaust by increasing radiation losses and thus reducing heat flux. It has been demonstrated that both the inner and outer divertor targets can reach nearly full detachment with total peak heat loads lower than 10 MW m⁻² and without notable impurity contamination in the core plasma. The heat loads on both targets contributed by radiation and neutrals are notable for the pronounced divertor detachment scenario. The simulation indicates that, to achieve a similar divertor condition, increasing the D puffing rate can significantly reduce the required Ar puffing rate. This causes a clear reduction in both the average Ar concentration and the effective ion charge number. Additionally, it is found that Ar has a higher compression in the inner divertor region due to the enhanced source-driven flow of recycling main ions in proximity to the outer divertor target. Furthermore, the erosion rate of tungsten divertor targets has been estimated using the DIVIMP code based on the background plasmas provided by SOLPS-ITER. The results indicate that the W erosion rate is generally within the acceptable lifetime requirement for the CFEDR divertor.