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Quasisymmetry can greatly improve the confinement of energetic particles andthermal plasma in a stellarator. The magnetic field of a quasisymmetricstellarator at high plasma pressure is significantly affected by the bootstrapcurrent, but the computational cost of accurate stellarator bootstrapcalculations has precluded use inside optimization. Here, a new efficientmethod is demonstrated for optimization of quasisymmetric stellaratorconfigurations such that the bootstrap current profile is consistent with thegeometry. The approach is based on the fact that all neoclassical phenomena inquasisymmetry are isomorphic to those in axisymmetry. Therefore accurateformulae for the bootstrap current in tokamaks, which can be evaluated rapidly,can be applied also in stellarators. The deviation between this predictedparallel current and the actual parallel current in the magnetohydrodynamicequilibrium is penalized in the objective function, and the current profile ofthe equilibrium is included in the parameter space. Quasisymmetricconfigurations with significant pressure are thereby obtained withself-consistent bootstrap current and excellent confinement. In a comparison offusion-produced alpha particle confinement across many stellarators, the newconfigurations have significantly lower alpha energy losses than many previousdesigns.

Optimization of quasisymmetric stellarators with self-consistent bootstrap current and energetic particle confinement