Optimizing omnigenity like quasisymmetry for stellarators

Abstract: Omnigenous magnetic fields, where the bounce-averaged radial drift vanishes, offer a promising solution to confine charged particles in fusion devices, particularly in stellarators. However, nonquasisymmetric omnigenity has remained underexplored due to the absence of a general optimization method. We introduce a novel approach for optimizing omnigenity. With simplicity comparable to quasisymmetry (QS) optimization, the new method unifies both QS and non-QS omnigenity optimization and can be further generalized to optimize configurations beyond omnigenity. Precisely omnigenous configurations with exceptional confinement and unprecedented compactness have been realized. Moreover, novel configurations like pseudosymmetry and piecewise omnigenity have been directly optimized for the first time. These advances enable efficient explorations of practical stellarator designs with enhanced confinement and engineering feasibility.