Phys. Rev. Lett. 124, 095001 (2020)

Magnetically confined fusion devices rely on electromagnets to generate magnetic fields to keep the extremely hot plasma in place. In stellarators, external coils with complicated shapes twist the magnetic field lines into a helical shape. This comes with a certain price tag. Per Herlander and colleagues have now proposed a concept that could relax constraints on the design of the magnetic field coils.

Herlander and colleagues showed that adding permanent magnets to a stellarator can simplify the design of the magnetic-field coils and, in principle, reduce the overall cost of the device. They theoretically studied a quasi-axisymmetric configuration with eight identical coils and permanent magnets. Although the permanent magnets cannot generate a toroidal magnetic field, they produce a poloidal flux and a rotational transform of the magnetic field. By shaping the plasma through permanent magnets, the requirements on the coils are less stringent. Future studies will have to address the feasibility of this proposal.