Optimizing a Quasi-Helically Symmetric Stellarator

Quasi-helically symmetric stellarator configurations over a range of number of field periods are optimized using the SIMSOPT code [M. Landreman, et. al., J. Open Source Software 6, 3525 (2021)]. The WISTELL collaboration developed optimized configurations with high degrees of quasi-helical symmetry, minimization of the radial drift velocity, improved neoclassical confinement, and improved confinement of energetic particles [A. Bader, et al., J. Plasma Physics 85, 905850508 (2019)]. These development efforts focused primarily on four- and five-field period configurations. For a reactor-scaled device, a larger aspect ratio and higher number of field periods may be beneficial. In this work, configurations over a range of number of field periods and aspect ratios are developed and tested. Coil configurations that both optimize the physics and meet engineering constraints will be examined. The effects of different coil configurations on energetic particle confinement will be examined using the SIMPLE code [C. Albert, et al., J. Plasma Physics 86, 815860201 (2020)].