Optimization of the Compact Stellarator with Simple Coils at finite-beta

An optimized stellarator at finite plasma beta is realized by single-stage optimization of simply modifying the coil currents of the Compact Stellarator with Simple Coils (CSSC)[Yu et al., J. Plasma Physics 88,905880306 (2022)]. The CSSC is an optimized stellarator obtained by direct optimization via coil shapes, with its coil topology similar to that of the Columbia Non-neutral Torus (CNT) [Pederson et al., Phys. Rev. Lett. 88, 205002 (2002)]. Due to its vacuum-based optimization, the CSSC exhibits detrimental finite beta effects on neoclassical confinement. The results of optimization show that the finite beta effects can be largely mitigated by reducing the coil currents of CSSC.