The Effects of Gas Puff Locations and Divertor Closure on Detachment Conditions in MAST-U

The effect of different fueling locations and divertor closure in the MAST-U tokamak is studied in detail with the SOLPS-ITER code to gain insights to detachment conditions in H-mode plasma experiments in conventional divertor (CD) configuration. The SOLPS simulation for MAST-U H-mode plasma reveals that changing fueling location significantly impacts the detachment condition. Fueling from the lower divertor (LD) in a closed geometry significantly enhances reductions on the peak heat flux and temperature at the lower outer divertor (LOD), enabling detachment at ~50% lower upstream density (n_e,sep) compared to midplane fueling. In the closed divertor configuration, LD fueling reduces peak electron temperature across the range of density scans and leads to a rollover in main ion flux at 40% lower n_e,sep than in the open divertor. These effects diminish under the midplane fueling. The analysis of all four scenarios (midplane/LD fueling in closed/open divertor) shows that divertor closure and localized fueling work in synergy to create the optimized neutral trapping and energy dissipation, promoting detachment onset at lower n_e,sep. This work demonstrates that divertor closure and localized fueling are both crucial to facilitate detachment onset at lower highlighting the importance of an integrated approach to divertor optimization.