"We built a first-of-a-kind, superconducting magnet. It required a lot of work to create unique manufacturing processes and equipment. As a result, we are now well-prepared to ramp-up for production," says Joy Dunn, head of operations at Commonwealth Fusion Systems (CFS). "We started with a physics model and a CAD design, and worked through lots of development and prototypes to turn a design on paper into this actual physical magnet." That entailed building manufacturing capabilities and testing facilities, including an iterative process with multiple suppliers of the superconducting tape, to help them reach the ability to produce material that met the needed specifications - and for which CFS is now overwhelmingly the world's biggest user.

We worked with two possible magnet designs in parallel, both of which ended up meeting the design requirements, she says. "It really came down to which one would revolutionize the way that we make superconducting magnets, and which one was easier to build." The design they adopted clearly stood out in that regard, she says.

In this test, the new magnet was gradually powered up in a series of steps until reaching the goal of a 20 tesla magnetic field - the highest field strength ever for a high-temperature superconducting fusion magnet. The magnet is composed of 16 plates stacked together, each one of which by itself would be the most powerful high-temperature superconducting magnet in the world.

The magnets are part of a new tokamak facility called SPARC, targeted for completion in 2025. A series of scientific papers published last year outlined the physical basis and, by simulation, confirmed the viability of the new fusion device. The papers showed that, if the magnets worked as expected, the whole fusion system should exceed scientific energy breakeven, for the first time in decades of fusion research. Citing the series of physics papers published last year, Brandon Sorbom, the chief science officer at CFS, says "basically the papers conclude that if we build the magnet, all of the physics will work in SPARC."