Exploratory Divertor Heat Load Studies for Compact Stellarator Reactors

Divertor heat load evaluation studies are being carried out for an example compact stellarator reactor configuration modeled after the National Compact Stellarator Experiment (NCSX). Using the field line tracing technique, an initial divertor plate geometry has been obtained, with one plate per field period, which covers 15% of the plasma surface area. A plate heat load peaking factor of 14 is acceptable with reasonable core and SOL radiation fractions in order to satisfy the engineering constraint of 10 MW/m peak heat load. Assessment of heat flux due to ejected energetic alpha particles is equally important for their contribution to the heat load. A particle gyro-orbit code follows these particles in the scrape-off layer (SOL) until they hit the divertor plates and the first wall, while the distribution of lost particles on the plasma surface can be calculated with a Monte Carlo guiding center code with collisions