Quasisymmetric stellarator equilibria optimized for good magnetic surfaces

Quasisymmetric stellarators with good magnetic surfaces boast the superior confinement properties of tokamaks. However, good magnetic surfaces are not guaranteed in three-dimensional toroidal magnetic fields. In general, magnetic islands or regions of chaotic fields will exist, which can degrade particle and energy confinement of the main plasma. Using the Stepped Pressure Equilibrium Code (SPEC) with the Green’s residue method in Simsopt [similar to Physics of Plasmas 28, 092505 (2021)], we show that magnetic islands can be eliminated while preserving good quasisymmetry, in a new equilibrium. Further, we identify an equilibrium with a pressure profile that is self-consistent with turbulent fluxes, using T3D+GX.