Coil Optimization for a Quasi-Helically Symmetric Stellarator*

Optimized coil configurations are developed for a quasi-helically symmetric stellarator using the FOCUS code [C. Zhu, et al., Plasma Phys. Contr. Fusion 60, 065008 (2018)]. Recent work has indicated that 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 85, 905850508 (2019)]. Preliminary coil configurations that both optimize the physics and meet engineering constraints have been obtained. In this work, the FOCUS code will be used to develop and analyze coil configurations for four-field and five-field period configurations with a set of poloidal field coils. The effects of different coil configurations on Ideal MHD stability, neoclassical transport and energetic particle confinement will be examined. 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.