Fast and Accurate Stellarator Optimization for Novel Physics Metrics*

The stellarator is a promising fusion reactor concept that can avoid many limitations of tokamaks, such as operating without current drive and softer stability limits. However, the large design space and lack of guaranteed confinement means significant numerical optimization is required of any feasible stellarator design. We present an overview of the new stellarator design and analysis results made possible by the DESC code suite. This software package couples equilibrium and optimization codes together to efficiently solve the numerical optimization problems required for next-generation stellarator designs. Unlike finite differences or adjoint methods, automatic differentiation provides access to exact derivatives of any objective function and allows the inclusion of more physics constraints, such as metrics for particle confinement and stability. We demonstrate optimization of MHD equilibria for omnigenity, mercier and ballooning stability, alpha particle confinement, neoclassical and turbulent transport, and coil feasibility metrics. We also show new results from coil and winding surface optimization along with free boundary equilibria and single stage optimization of coils and equilibrium simultaneously.