ITER, the world’s largest fusion experiment, has moved a step closer to operational status with the arrival of the special magnets needed for the reactor’s core in southern France. This milestone marks the culmination of a two-decade-long design process, involving fabrication efforts spanning three continents.
As the quest for carbon-free energy intensifies, nuclear fusion emerges as a promising solution, offering the potential for on-demand energy production. Recent advances have shown that energy gain from nuclear fusion is achievable. More than 30 countries are collaborating on the International Thermonuclear Experimental Reactor (ITER) project in France. ITER employs the tokamak approach, where hydrogen fuel is injected into a torus-shaped vacuum chamber, heated to create plasma, and replicate conditions akin to the Sun. At temperatures reaching 150 million degrees Celsius, fusion reactions occur.
Containing this plasma within the reactor’s walls requires the use of giant superconducting magnets. ITER’s design utilizes niobium-tin and niobium-titanium for its magnets. These coils are energized with electricity and cooled to just four degrees above absolute zero (-269 degrees Celsius) to become superconducting.
ITER’s magnetic system comprises three components to create the magnetic cage needed to confine the plasma. Eighteen D-shaped toroidal magnets form the outer donut shape, while six additional magnets circle the tokamak horizontally to control plasma shape. A central solenoid generates current in the plasma with energy pulses. The plasma current will peak at 15 million amperes, setting a record for tokamaks globally. The magnetic field generated will be 250,000 times stronger than Earth’s, with a total magnetic energy of 41 gigajoules.
Each toroidal magnet stands 55 feet tall, 30 feet wide, and weighs 360 tons. The fabrication process began with niobium-tin strands wound with copper and inserted into a steel jacket, forming a conductor. Over 54,000 miles of these strands were required. The conductor was shaped into double spiral trajectories, heated, and inserted into stainless steel plates, then insulated, laser-welded, and injected with resin. Seven such double pancakes formed a winding pack, the core of the magnet, encased in a 200-ton stainless steel structure to withstand plasma forces and fusion energy.
ITER’s advancement marks a significant leap towards realizing a sustainable and powerful energy source, harnessing the immense power of fusion.
