ITER is the 35-nation experimental tokamak under construction in southern France, designed to produce 500 megawatts of 📝fusion power from 50 megawatts of injected heating — a plasma energy gain of 📝Q equals 10.
The name began as an acronym for International Thermonuclear Experimental Reactor, but the project now emphasizes the Latin reading — iter, "the way." ITER is the largest 📝Tokamak ever attempted: a major radius of 6.2 meters, a plasma volume of 840 cubic meters, and a magnet system wound from niobium-tin, a 📝low-temperature superconductor, all assembled at Saint-Paul-lez-Durance under an agreement signed in 2006 by China, the European Union, India, Japan, Korea, Russia, and the United States. An updated baseline announced in 2024 places the start of full 📝deuterium-📝tritium operation in 2039.
ITER is often confused with a power plant; it is not one. Its 500 megawatts of fusion power will be dispersed as heat, never converted to electricity, and its Q of 10 measures plasma gain, not whole-facility gain — the 📝Q_plasma vs Q_engineering distinction. The site will draw more electricity from the grid than the plasma produces. Generating net electricity is deferred to the 📝DEMO class of successor plants in public roadmaps. ITER's actual product is a 📝burning plasma — one heated chiefly by its own 📝D-T reactions — at a scale no experiment has reached, along with the licensing, 📝remote-handling, and tritium-plant experience a first generation of power reactors will draw on.