Integrating edge exhaust in SPARC L-mode scenario development

High performance L-modes on SPARC operate with high plasma current (∽8.5MA) and poloidal magnetic field (Bpol,omp∽3T), resulting in a narrow heat flux decay length of λ_q∽0.6mm (Brunner scaling). The Q>1 scenario requires just ∽10MW of heating power, but because of the narrow SOL width the predicted unmitigated heat fluxes in L-mode will be 20MW/m² perpendicular to the target. To avoid recrystallization or excessive sputtering of the tungsten divertor targets, scenario development in SPARC will target radiative, impurity-seeded regimes. A model for impurity-seeded core and edge radiation has recently been integrated into the CFS-POPCON 0D scoping tool. Here, we use a two-point-model and a Lengyel-model to determine the xenon and neon concentrations required to achieve a given target temperature, and calculate a consistent dilution and effective charge (Z_eff). A scenario achieving Q>1 in L-mode was identified with a surface heat flux of 4MW/m², a 40eV target and a 140eV upstream temperature. This scenario uses 60% core radiation and 80% edge radiation, resulting in a fuel dilution of ∽85% and a Z_eff of ~2.5. The scenario is now being studied using higher-fidelity core and edge simulations.