Gyrokinetic study of transport in the Scrape-Off Layer with SPARC-relevant parameters

As fusion devices approach reactor-scale conditions, it is crucial to manage the heat poured into its walls and divertor. Due to the high temperatures of burning plasmas, fluid theory becomes unreliable not only in the core, but also in boundary plasmas. For this reason, first-principles gyrokinetic theory and modeling is important for understanding turbulent transport from the core to the edge and scrape-off layer (SOL) of burning-plasma reactors. This poster will present results obtained using the gyrokinetic code Gkeyll to perform simulations in a simple-model helical geometry with SPARC's characteristic magnetic field, temperature and density. In particular, we have studied the evolution of the temperature and density profiles and the distribution of the heat flux along the divertor when we vary the pitch angle of magnetic field lines in the SOL. These profiles are determined by the competition of transport across the field lines, dominated by the interchange instability and stabilized by sheath and FLR effects; versus the transport along the field lines, determined by the time that thermal particles take to reach the divertor plates from the mid-plane. Analytical work and numerical simulations support the conclusion that by decreasing the pitch angle, the resulting increase in the connection length will reduce the stabilization from sheath effects. This makes interchange-driven transport more predominant, resulting in broader profiles and a larger pressure gradient scale length.