Novel optimized stellarator configurations

Several new stellarator configurations are presented, generated using the new stellarator optimization framework SIMSOPT. It is shown that both quasi-axisymmetry (QA) and quasi-helical (QH) symmetry can be obtained to higher precision than demonstrated previously, both on a single flux surface and throughout a volume. A number of new QA configurations are presented that have much improved confinement of fusion-produced alpha particles compared to previous QA configurations. Finally, a method is demonstrated to optimize a stellarator's geometry to eliminate magnetic islands and achieve other desired physics properties at the same time. In this approach, two equilibrium calculations are run at each iteration of the optimization: one that enforces the existence of magnetic surfaces (VMEC), and one that does not (SPEC), with island residues penalized in the objective function to bring the two magnetic field representations into agreement during the optimization.