Commonwealth Fusion Systems installs reactor magnet, lands deal with Nvidia

Commonwealth fusion systems (CFS) said Tuesday at CES 2026 that it had installed the first magnet in its Sparc fusion reactor, the demonstration device it hopes to turn on next year.

The magnet is the first of 18 that, when the reactor is completed, will create a doughnut-like shape that will produce a powerful magnetic field to trap and compress superheated plasma. If all goes well, that plasma will release more energy than is needed to heat and compress it.

After decades of promise and delays, fusion energy appears to be just around the corner: CFS and its competitors are locked in a race to deliver the first electrons to the electricity grid sometime in the early 2030s. If successful, fusion energy could unlock virtually unlimited clean energy in a package that resembles a traditional power plant.

Major components of Sparc’s magnets have been completed and the company expects to install all 18 magnets by the end of the summer, said Bob Mumgaard, co-founder and CEO of CFS. “It’s going to be pop, pop, pop for the first half of this year as we put together this revolutionary technology.”

Once installed, the D-shaped magnets will sit upright on a 25-foot-wide, 75-ton stainless steel circle known as a cryostat, which was placed in place last March. The magnets themselves weigh about 24 tons each and can generate a magnetic field of 20 teslas, about 13 times stronger than a typical MRI machine. “It’s the type of magnet you could use to lift an aircraft carrier, for example,” Mumgaard said.

To achieve that strength, the magnets are cooled to -253˚ C (-423˚ F) so they can safely conduct more than 30,000 amps of current. Plasma will burn in the donut at a temperature of more than 100 million degrees Celsius.

To iron out as many kinks as possible before Sparc is turned on, CFS said Tuesday it is working with Nvidia and Siemens to develop a digital twin of the reactor. Siemens provides the design and manufacturing software, which allows the company to collect data to enter into Nvidia’s Omniverse libraries.

That won’t be CFS’s first simulation — the company has already run numerous simulations to predict the performance of different parts of the reactor — but existing efforts are producing isolated results, Mumgaard said. With the digital twin, he said, “these are no longer isolated simulations used just for design. They will be next to the physical thing all the way, and we will be comparing them against each other all the time.”

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

Building Sparc has been a costly undertaking. CFS has raised nearly $3 billion to date, including an $863 million Series B2 round in August with 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 dollars more, CFS estimates.

Mumgaard hopes that digital twins and AI technology will help the company deliver fusion energy to the power grid sooner rather than later. “As machine learning tools get better and representations become more accurate, we could see it getting even faster, which is good because we desperately need fusion to reach the power grid,” he said.

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