The Effects of Gas Puff Locations and Divertor Closure on Detachment Conditions in MAST-U
The effect of different D2 fueling locations and divertor closure in the MAST-U is studied in detail with the SOLPS-ITER code to gain insights to detachment physics in H-mode plasma experiments in conventional divertor (CD) configuration. The SOLPS-ITER simulations for MAST-U H-mode plasma reveals that changing D2 fueling location significantly impacts the detachment condition. Under lower outer divertor (LOD) fueling, the total power loss at the lower outer divertor (LOD) is higher compared to the midplane fueling scenario for the same electron density at the outboard midplane side (nOMP e,sep ). With LOD fueling in closed configuration, the analysis demonstrates substantial reductions on the peak heat flux and electron temperature at the lower outer divertor (LOD), facilitating the detachment onset due to an increased D neutral density and enhanced radiation, while suppressing carbon (C) sputtering. The closed divertor shows higher neutral trapping capability under both midplane and LD fueling. With LD fueling, the peak plasma temperature (Te) show greater reduction in the closed divertor compared to the open divertor and the roll over of main ion flux (Γi) happens at ∼ 40% lower nOMP e,sep in the closed divertor. These differences between divertor closure diminish when the midplane fueling is used. The analysis of all four scenarios (midplane/LD fueling in closed/open divertor) show that divertor closure and localized fueling work in synergy to create the optimized neutral trapping and energy dissipation, promoting detachment onset at lower nOMP e,sep . This work demonstrates that divertor closure and the localized fueling are both crucial to facilitate detachment onset at lower nOMPe,sep , highlighting the importance of an integrated approach to divertor optimization