SOLPS-ITER modelling of Liquid Lithium Divertor for a Fusion Nuclear Science Facility (FNSF)

The scrape-off layer heat flux width (λ_q) is an important parameter for the plasma facing components in fusion devices because it can determine the peak energy flux to the divertors. Here, we have investigated the impact of λ_q on the divertor and upstream plasma conditions for the Fusion Nuclear Science Facility (FNSF) with fast flowing liquid lithium (Li) divertors. The anomalous radial transport values, χ_⊥e,i = 1.0 m²/s and D_⊥ = 0.3 m²/s are used as a base case, resulting in λ_q mapped to the outer midplane of 3-4 mm. The radial transport values are modified to provide three different λ_q. The main gas puffing and neon (Ne) seeding rate are then adjusted to maintain the upstream electron separatrix density ~ 10²⁰ m^-3 and Li is sourced into the system. The Li ion concentration is increased in the upstream region as λ_q is reduced, while the electron temperature (T_e) profile becomes narrower_. Consequently, Li escapes along the periphery regions and transports toward the upstream region due to lower T_e. The effect of Li sourcing location and private flux region PFC geometry will be presented. Coupling between the liquid Li MHD heat transfer code and SOLPS has been performed, and the radial profile of evaporated flux is imposed according to the liquid metal (LM) surface temperature. Divertor plasma parameters are significantly affected for the higher evaporation Li divertor.