Quasi-Helically Symmetric Stellarator Optimization with Poloidal Field Coils

Quasi-symmetry provides a pathway for improved neoclassical confinement in stellarators. Recent work has indicated that combining optimization of quasi-helical symmetry and minimization of the radial drift velocity can lead to configurations with improved neoclassical confinement and improved confinement of energetic particles [A. Bader, et al., J. Plasma Physics \textbf{85}, 905850508 (2019)]. An effort is underway to develop coil configurations that both optimize the physics and meet engineering constraints. The FOCUS code was developed to flexibly explore the configuration space in coil optimization [C. Zhu, et al., Plasma Phys. Contr. Fusion \textbf{60}, 065008 (2018)]. In this work, the FOCUS code will be used to develop and analyze coil configurations for five-field period configurations with quasi-symmetry and enhanced energetic particle confinement. We will examine modular coil configurations with and without a set of poloidal field coils and analyze the effects of different coil configurations on Ideal MHD stability, neoclassical transport and energetic particle confinement. This work will include optimization of a coil set for a midscale stellarator experiment and the development of a coil set for a reactor scale device.