The most powerful pulsed superconducting magnet system ever built is now complete, and will soon be part of the world’s grandest energy experiment.
The system is the Central Solenoid of the International Thermonuclear Experimental Reactor (ITER), a towering magnet core built and tested in the United States and destined for southern France, where the international project is assembling its gigantic tokamak. The magnet system will serve as the electromagnetic “heart” of the reactor, strong enough—according to ITER—to lift a freaking aircraft carrier.
For the uninitiated: Tokamaks are doughnut-shaped vessels that contain superheated plasma for nuclear fusion, the energetic reaction that powers stars like our Sun. Tokamaks constrain the plasma by generating very strong magnetic fields, hence the importance of ITER’s Central Solenoid.
ITER is dedicated to validating nuclear fusion as a viable energy source, though none of the reactor’s output will be used to power anything. ITER is simply a gigantic and expensive technology demonstrator, one that’s inching increasingly closer to actually flipping the “on” switch to recreate the power of the Sun here on Earth. It’s an expansive collaboration involving over 30 countries, aiming to prove that fusion energy—basically, slamming atoms together until they produce different atoms, releasing massive amounts of energy in the process—can be harnessed and scaled into a commercially viable and essentially limitless power source.
The newly completed magnet system isn’t going to work alone. The Central Solenoid joins six massive ring-shaped Poloidal Field magnets built and delivered from Europe, China, and Russia, forming a 3,000-ton (2,721 tonne) system of superconductors cooled to -452.2 degrees Fahrenheit (-269 degrees Celsius). Together, the supercooled magnets will trap and shape scorching plasma at 270 million degrees Fahrenheit (50 million degrees C)—ten times hotter than the Sun’s core—until atomic nuclei fuse and let out a tenfold energy return.
Commercially viable fusion has long been the clean energy grail, and ITER’s setup is expected to generate 500 megawatts of energy from just 50 megawatts of input. That kind of power return would mark the start of self-sustaining “burning plasma”—though there’s a long road to that goal.
Private companies are attempting to demonstrate smaller-scale tokamak designs as a potential way to realize the future of fusion, though neither approach has had its breakthrough moment to date.
In 2022, the U.S. Department of Energy and Lawrence Livermore National Laboratory announced net energy gain in a fusion reaction at the National Ignition Facility—but even that high-water-mark did not account for “wall power” used in the experiment, making it another incremental step in the marathon towards viable fusion power, rather than a shortcut to the finish line.
ITER isn’t just a physics experiment—it’s a geopolitical flex. Despite tensions between member countries, the project has delivered on component construction and hit its 2024 construction targets. (The collaboration also launched a private sector fusion project last year for sharing data and furthering the project’s R&D goals). The U.S. built the solenoid and support structure, Europe is handling the vacuum chamber, Russia provided the reactor’s massive superconductors and busbars, while Korea, Japan, China, and India have all contributed vital parts of the tokamak’s core.
“With ITER, we show that a sustainable energy future and a peaceful path forward are possible,” said Pietro Barabaschi, ITER’s Director-General, in a collaboration release. Of course, ITER has yet to realize the “sustainable energy future” part of its project, so don’t hold your breath for the peaceful future, either.
Now in its assembly phase, ITER is building up steam towards its actual goals—a slight increase in momentum from the collaboration’s plodding steps in producing its constituent parts. If it works, this magnetized machine could be a watershed moment towards a carbon-free energy future—even if it does not contribute to the power grid itself.
English (US) ·