The first quasi-axisymmetric permanent magnet stellarator

Fusion energy has the potential to meet the world's demand for clean energy. The stellarator was first invented in 1951 as a potential device for fusion reactions. It uses external coils to generate a magnetic field as well as rotational transform to confine the fusion plasma in a toroidal region. Early stellarators had poor plasma confinement due to large neoclassical loss and MHD instabilities. With the development of more advanced design tools, modern stellarators have been optimized to minimize neoclassical loss (and to be MHD stable). Today, like Windlestien 7X, Stellarators have complex designs that make maintenance and access difficult. It has been proposed by Mike Zarnstorff, et. al.[1] that using planer coils and permanent magnets to generate a magnetic field can significantly reduce the difficulty in building a stellarator. A permanent magnet stellarator would make construction much easier, cheaper, provide us with more freedom for optimizing the magnetic field, make the design and construction modular, and would enable rapid prototyping. ​​We are building the world's first quasi-axisymmetric permanent magnet stellarator(MUSE)[2] to demonstrate the feasibility of this approach for building optimized stellarators.

[1] 2020 Helander, et. al., Phys. Rev. L., 124, 095001

[2] 2022 Qian, et. al., Nucl. Fusion, 62, 084001