Commonwealth Fusion Systems installs the reactor magnets, and closes a deal with Nvidia

Commonwealth Fusion Systems (CFS) said Tuesday at CES 2026 that it has installed the first magnets in its Sparc fusion reactor, an experimental device it hopes to have operational next year.

The magnet is the first of 18 that, when the reactor is complete, will create a donut-like shape that will produce a powerful magnetic field to confine and compress the super-hot plasma. If all goes well, that plasma will release more energy than it takes to heat and compress it.

After decades of promises and delays, nuclear fusion power appears to be just around the corner, with CFS and its competitors in a race to deliver the first electrons to the grid sometime in the early 2030s. If successful, fusion power could unleash nearly limitless clean energy in a package resembling a conventional power plant.

Major components of the Sparc magnets have been completed, and the company expects to have all 18 elements installed by the end of the summer, said Bob Mumgaard, co-founder and CEO of CFS. “There will be buzz, buzz, buzz throughout the first half of this year as we put together this revolutionary technology.”

When installed, the D-shaped magnets will be placed upright on a 24-foot-wide, 75-ton stainless steel circle known as the cryostat, which was put in place last March. Each magnet weighs about 24 tons and can generate a 20 Tesla magnetic field, about 13 times stronger than a typical MRI machine. “It’s the kind of magnet you could use to lift an aircraft carrier,” Mumgaard said.

To achieve this strength, the magnets will be cooled to -253°C (-423°F) so they can safely deliver over 30,000 amps of current. Inside the donut, the plasma will burn at a temperature of more than 100 million degrees Celsius.

To iron out as many kinks as possible before Sparc is operational, CFS said Tuesday it is working with Nvidia and Siemens to develop a digital twin of the reactor. Siemens is supplying the design and manufacturing software, which will help the company collect data for input into Nvidia’s Omniverse libraries.

Mumgaard said this wouldn’t be CFS’s first simulation — the company has already run several simulations to predict the performance of different parts of the reactor — but current efforts provide results in isolation. With the digital twin, “These are no longer isolated simulations used just for design. They will be side by side with the physical thing all the way through, and we will constantly be comparing them to each other,” he said.

The hope is that CFS can run experiments or tweak parameters in the digital twin before applying it to Sparc itself. “It will work side by side so we can learn from the machine faster,” he said.

Building Sparc was an expensive endeavor. CFS has raised nearly $3 billion to date, including an $863 million Series B2 round in August that included investments from Nvidia, Google, and nearly three dozen other investors. The company’s first commercial-scale power plant, ARC, will be the first of its kind. As a result, it will likely cost several billion more dollars, the Committee on World Food Security estimates.

Mumgaard hopes digital twins and artificial intelligence technology will help the company get fusion power to the grid sooner rather than later. “As machine learning tools get better, and as the representations get more accurate, we can see it going faster, which is good because we have a pressing need for fusion to get into the network,” he said.

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