The last piece of this magnet system-the sixth module of the Central Solenoid-was produced and tested in the U.S. It will soon be integrated into the ITER Tokamak in southern France, where it will function as the system's primary magnetic driver, capable of generating forces strong enough to lift an aircraft carrier.
This central magnet operates alongside six ring-shaped Poloidal Field (PF) magnets, supplied by Russia, Europe, and China. Together, they form the electromagnetic core of the ITER Tokamak reactor, a donut-shaped chamber where fusion reactions will take place. When fully assembled, the magnet system will weigh nearly 3,000 tons.
To produce fusion, a few grams of hydrogen fuel-deuterium and tritium-are injected into the Tokamak. The magnet system then generates a plasma by ionizing the gas and confining it in a magnetic field. External systems heat this plasma to 150 million degrees Celsius, at which point the nuclei begin to fuse, releasing immense energy.
ITER aims to produce 500 megawatts of fusion power from only 50 megawatts of input, achieving a tenfold energy gain and creating a largely self-sustaining "burning plasma." It is a critical step toward realizing commercial fusion energy.
ITER also stands as a rare example of global scientific cooperation. Its seven members-China, Europe, India, Japan, Korea, Russia, and the United States-have contributed thousands of components built by companies across three continents.
"What makes ITER unique is not only its technical complexity but the framework of international cooperation that has sustained it through changing political landscapes," said ITER Director-General Pietro Barabaschi. "This achievement proves that when humanity faces existential challenges like climate change and energy security, we can overcome national differences to advance solutions."
By April 2025, ITER had met 100% of its construction targets. The first vacuum vessel sector was installed in the Tokamak pit, slightly ahead of schedule. The organization has also launched initiatives to engage the growing private sector in fusion development, including a 2025 workshop to foster public-private technological collaboration.
Members contribute primarily by supplying components. Europe, as host, covers 45% of the project cost. The other members each contribute 9%, with all having full access to the resulting intellectual property. The U.S. built all six Central Solenoid modules and the massive exoskeleton needed to contain its forces, in addition to producing 8% of the Toroidal Field magnet superconductors.
Russia has supplied a 9-meter PF magnet, large quantities of NbTi and Nb3Sn superconductors, high-power busbars, and vacuum vessel port plugs. Europe built four PF magnets, ten Toroidal Field coils, and five vacuum vessel sectors. China manufactured PF6, supplied the majority of PF superconductors, correction coils, and magnet feeders. Japan produced eight Toroidal Field coils, the Central Solenoid's superconducting strands, and its casings. Korea contributed 20% of Toroidal Field superconductors, thermal shields, precision tooling, and four vacuum vessel sectors. India built the 30-meter-high cryostat and provided cryolines, the cooling system, shielding, and plasma heating elements.
In total, ITER's magnet systems include 10,000 tons of superconducting magnets made from over 100,000 kilometers of superconducting strand.
Fusion's electromagnetic heart is now complete.
Research Report:Fusion's Electromagnetic Heart: Technical Specifications of ITER Magnets
Related Links
Oak Ridge National Laboratory
ITER
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