Nuclear Fusion’s New Idea: An Off-the-Shelf Stellarator
Fast prototyping revives a 70-year-old reactor design
Tom Clynes | 28 Oct 2024

For a machine that’s designed to replicate a star, the world’s newest stellarator is a surprisingly humble-looking apparatus. The kitchen-table-size contraption sits atop stacks of bricks in a cinder-block room at the Princeton Plasma Physics Laboratory (PPPL) in Princeton, N.J., its parts hand-labeled in marker.

The PPPL team invented this nuclear-fusion reactor, completed last year, using mainly off-the-shelf components. Its core is a glass vacuum chamber surrounded by a 3D-printed nylon shell that anchors 9,920 meticulously placed permanent rare-earth magnets. Sixteen copper-coil electromagnets resembling giant slices of pineapple wrap around the shell crosswise.

The arrangement of magnets forms the defining feature of a stellarator: an entirely external magnetic field that directs charged particles along a spiral path to confine a superheated plasma. Within this enigmatic fourth state of matter, atoms that have been stripped of their electrons collide, their nuclei fusing and releasing energy in the same process that powers the sun and other stars. Researchers hope to capture this energy and use it to produce clean, zero-carbon electricity.

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Graduate students did the meticulous work of placing and securing the magnets. “This is a machine built on pizza, basically,” says Cowley, PPPL’s director. “You can get a lot out of graduate students if you give them pizza. There may have been beer too, but if there was, I don’t want to know about it.”

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