The most recent deliveries included busbars and leads for electrical connections between the magnet modules. All six modules, the support structure, and tooling components had been delivered earlier. ITER is backed by a coalition including the U.S., European Union, China, India, Japan, South Korea and Russia, and is designed as a research facility to demonstrate sustained net-energy fusion reactions—not to produce power for the commercial grid.

"The completion of the central solenoid magnet highlights the capability of the United States to design and deliver the world's most complex fusion systems," said Kevin Freudenberg, U.S. ITER interim project director. "Congratulations to the entire team who contributed, including those here at Oak Ridge National Laboratory who led the work, and our suppliers who fabricated critical components."

The central solenoid—a 59-ft-tall, 14-ft-wide superconducting assembly—was fabricated over a 15-year manufacturing effort at the General Atomics Magnet Technologies Center in Poway, Calif.

Each of the six modules weighs more than 135 tons and is wound from approximately 3.7 miles of niobium-tin superconducting cable sourced from Japan.

As part of a construction risk-management strategy, General Atomics also produced a seventh spare module that is held in reserve should any of the six primary modules need replacement. The completed assembly forms part of a larger magnetic system weighing 3,300 tons that interacts with nine vacuum vessel sectors inside the tokamak complex.

The fabrication challenge was unlike anything previously attempted in magnet manufacturing. "We're talking about orders of magnitude of scale," said Nikolai Norausky, program manager for the central solenoid project at General Atomics, during an August 2025 ceremony at the Poway facility marking the project's completion.

"We had to develop a modern supply chain,” he added. “Often our suppliers were dealing with the largest, or the heaviest or the most precise aspects of their technologies, and we had to bring all that in to develop the manufacturing know-how, and the tooling, in order to produce the central solenoid magnets."

Assembly is underway in southern France under the direction of the ITER Organization, with technical support provided through an agreement with the U.S. ITER project team at Oak Ridge. 

As of April, five of the six modules had been stacked, with the sixth—which arrived last September—scheduled to be added to the stack later this year, according to the ITER Organization.

Once complete, a compression structure will apply downward precompression to the module stack before the entire assembly is moved into the center of the tokamak pit.

The execution requirements for the milestone mirror those of the broader ITER project. ENR reported in July 2020 that building the tokamak's components to minute tolerances would be "like assembling a three-dimensional puzzle on an intricate timeline," in the words of then-ITER Director General Bernard Bigot.

The 23,000-tonne tokamak—more than three times the weight of the Eiffel Tower—is housed in a heavily reinforced concrete, seven-story building on a 180-hectare site near Saint-Paul-lez-Durance, 47 miles north of Marseille along the Mediterranean coast.

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Costs, Policy Scrutiny Mount

As ENR previously reported in July 2020, ITER was running about one decade behind schedule and about 50% over earlier cost estimates. Outside observers have cited total program costs as high as $65 billion, though ITER officials dispute that figure, noting that member nations contribute primarily through in-kind fabricated systems. The European Commission's current program cost, benchmarked in Euros, stands at approximately €22 billion.

The Trump administration's fiscal 2026 U.S. Dept. of Energy budget request proposed reducing ITER funding as part of what it described as a “reassessment of how the project fits” within U.S. fusion strategy—a policy shift that arrives as U.S. ITER formally closes out its central solenoid delivery obligations.

The supply chain ecosystem developed over the endeavor’s construction is increasingly informing commercial fusion development. ITER Head of Communication Laban Coblentz told RealClearScience in February 2025 that, a decade ago, there were perhaps five fusion companies globally; that number has since grown to roughly 45, growth he described as paralleling ITER manufacturing milestones.

"I think this approach, maybe inadvertently, has created a global fusion supply chain," Coblentz said. "As private-sector companies are gaining momentum, we are seeing them use ITER supplies to tackle their designs."

Livermore, Calif.-based Inertia Enterprises, a startup founded in 2024 to commercialize laser-based inertial confinement fusion technology developed at Lawrence Livermore National Laboratory, raised $450 million in Series A financing and aims to begin construction of a grid-scale pilot plant by 2030.

Co-founder and Chief Technology Officer Mike Dunne told ENR in February 2026 that because the company is leveraging known physics, "we can confidently focus our efforts and investments on scaling technology and building a manufacturing supply chain that can deliver fusion power to the grid."

Developer Commonwealth Fusion Systems, based in Massachusetts, gained $863 million from global tech investors in its latest funding round late last year, with its total at nearly $3 billion, to advance work on a planned 400-MW power plant in Virginia to produce fusion energy at commercial scale using high-temperature superconducting magnets developed in partnership with MIT. That plant is set for construction start in 2027, the firm said, adding that its smaller pilot plant in Devens, Mass., is expected to operate next year.

Last month, Commonwealth applied to multi-state grid operator PJM Interconnection for grid connection, the first fusion company to take that step.