Impurity seeding studies in MAST-U

The effect of nitrogen seeding on H-mode plasmas in MAST-U is studied using the SOLPS-ITER code. Two different divertor configurations and D and N seeding rates have been scanned to study the effects in detail and create a scope for our database. The results of these simulations show that the closed divertor improves impurity control, achieving detachment at lower upstream densities compared to its open counterpart along with a higher impurity enrichment peak. We have also observed that the leakage of N upstream is due to the difference in both N flows and N ionization source locations in agreement with previous experiments and modeling at DIII-D (Casali PoP 2020, Casali NF 2020). The power radiated in the divertor is roughly 50% higher in the closed divertor compared to the open, with most of this power loss arising from ion-neutral interactions. This work contributes to a deeper understanding of divertor physics in H-mode MAST-U experiments and offers practical insights into optimizing detachment conditions through controlled impurity seeding and tailored magnetic geometries.