Image Courtesy: US Iter
The United States has completed delivery of a key component for the world’s largest nuclear fusion project, sending the final parts of a 135 ton central solenoid magnet to the ITER facility in southern France. The magnet, often described as the “beating heart” of the reactor, is essential for generating and maintaining the plasma required for fusion.
The deliveries mark the end of a 15 year manufacturing effort led by the US ITER program, with fabrication carried out at General Atomics in California. The final shipment included critical electrical components such as busbars and leads, completing the package needed for integration into the reactor, according to the ITER Organization.
The central solenoid stands 18 meters tall and is made up of six individual modules, each weighing over 122 tonnes. These modules are constructed using roughly six kilometers of niobium tin superconducting cable, enabling them to carry extremely high electrical currents without resistance. Together, they form part of a magnetic system weighing around 3,000 tonnes, designed to control and confine plasma inside the reactor.
In a fusion system like ITER, the solenoid plays a critical role. It induces the magnetic flux needed to initiate plasma and sustain the current during operation. The reactor itself is designed to produce 500 megawatts of fusion power for short durations, using about 50 megawatts of input heating power, though additional electrical input is required to run the overall system.
Assembly is currently underway at the ITER site in Cadarache, France, under the supervision of the ITER Organization. Five of the six modules have already been stacked, with the final module expected to be added later in 2026. Once assembled, a compression structure will apply force to stabilize the stack against the intense electromagnetic forces generated during operation.
To reduce technical risk, a seventh spare module was also built. Earlier in 2025, the US team delivered a large external support structure designed to hold the magnet in place. This exoskeleton will help manage the mechanical stress created when the system is active.
ITER is an international collaboration aimed at demonstrating the feasibility of fusion as a carbon free energy source. Unlike conventional power plants, the facility will not supply electricity to the grid. Instead, its goal is to show that fusion reactions can produce more energy than they consume under controlled conditions.
The completion of the central solenoid marks a significant milestone in the project, highlighting the scale and complexity involved in building experimental fusion systems. It also reflects ongoing global efforts to explore fusion as a long term energy solution.
