Optimizing fusion power plant designs for negative triangularity through FUSE simulations*

The negative triangularity (NT) campaign recently completed at DIII-D has gained interest in NT-optimized fusion pilot plant (FPP) designs. Compared to positive triangularity (PT) configurations, NT configurations offer significant advantages, including the absence of edge localized modes and reduced heat loads on the divertor. FUSE is a computational framework designed for holistic simulations of fusion power plant facilities. It integrates key plasma physics processes—equilibrium, transport, heating & current drive, and stability—with crucial facility aspects, such as neutronics, structural mechanics, thermal cycle design, tokamak poloidal build, magnet coil design, first wall design, and costing. FUSE's strength lies in its capability for constrained multi-objective optimization, allowing exploration of a broad design space while meeting economic and engineering requirements. In a recent study within FUSE, a constrained multi-objective optimization was performed to minimize capital costs and operational risks by maximizing q95. This exploration of the broad tokamak design space resulted in over 200,000 whole facility simulations. These simulations reveal that both PT and NT offer viable design spaces; however, PT configurations tend to be less expensive due to the increased plant size required for NT.