We present the optimization of compact quasi-axisymmetric stellarators with aspect ratio as low as A = 2.4 and varying number of field periods. This previously unexplored optimization space has the striking feature that the symmetry-preserving perturbations remain mostly on the inboard side, and that the axisymmetric volume is large compared to previous designs. Configurations of two, three, and four field periods are presented which feature an average external rotational transform of 0.1, expected to act stabilizing, while obeying quasi-symmetry sufficiently enough to provide confinement to alpha particles at a typical reactor scale. We highlight the impact of different physics constraints on the achievable quasi-symmetry and optimized plasma boundaries, and discuss the trade-offs faced in the choice of the number of field periods.
This paper presents the optimization of compact quasi-axisymmetric stellarators, a type of fusion reactor design. The researchers explored a previously unexplored design space, achieving compact stellarators with aspect ratios as low as 2.4 and different numbers of field periods. These designs feature a large axisymmetric volume and an expected stabilizing average external rotational transform of 0.1, while maintaining good confinement of alpha particles.
Shape optimization of surface-current-model tokamaks with elongated cross-sections