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 this project, we study the dependance of the temperature, density and divertor heat flux profiles on the magnetic configuration and simulation parameters. As the pitch angle of the magnetic field lines in the SOL is decreased, it is expected that the interchange stability driving transport across the field lines is enhanced and the characteristic time of transport along the field lines increases as well. Analytical work and numerical simulations support the conclusion that this results in broader profiles and a larger pressure gradient scale length, which could help to spread the heat load along the divertor plates. In addition, we study the dependance on the simulation box radial length to observe how our boundary conditions affect the decay lengths of the profiles. Ongoing work includes evaluating the driving terms from gyrokinetic equations with the objective of deriving a scaling law for the pressure decay length of the SOL, and comparing it with previous predictions from fluid theory and modeling.