Optimized Quasisymmetric Stellarators Are Consistent with the Garren-Boozer Construction

Plasma Phys. Control. Fusion 61, 075001 (2019)https://ireap.umd.edu/10.1088/1361-6587/ab19f62019Journal ArticlePlasma, Accelerator, and Nuclear Physics

Most quasisymmetric stellarators to date have been designed by numerically optimizing the plasma boundary shape to minimize symmetry-breaking Fourier modes of the magnetic field strength B. At high aspect ratio, a faster approach is to directly construct the plasma shape from the equations of quasisymmetry near the magnetic axis derived by Garren and Boozer (1991 Phys Fluids B 3 2805). Here we show that the core shape and rotational transform of many optimization-based configurations can be accurately described by this direct-construction approach. This consistency supports use of the near-axis construction as an accurate analytical model for modern stellarator configurations.