JET — the Joint European Torus at Culham in the United Kingdom — was the tokamak that set the record for total 📝fusion energy from deuterium-tritium fuel before retiring in December 2023.
Operating from 1983 to 2023, JET was for four decades the largest 📝Tokamak in the world and one of only two ever to run the full 📝D-T reaction — the other being TFTR at Princeton. Its 1997 campaign produced a peak of 16 megawatts of fusion power, a record that stood for a quarter century; its final deuterium-tritium campaigns delivered 59 megajoules of fusion energy in 2021 and 69 megajoules in 2023, the largest totals ever released by a confined 📝plasma.
JET is best understood against 📝ITER, the machine it spent its later career serving. Where ITER is designed for tenfold energy gain, JET's best shots reached a Q near 0.67 — but at roughly one-tenth ITER's plasma volume, with copper rather than superconducting magnets, and on pulse lengths of seconds. From 2011 it operated with a 📝beryllium-and-📝tungsten "ITER-like wall" to rehearse ITER's material choices, and its 📝tritium handling plant remained the only one integrated with an operating tokamak. Much of the empirical basis for ITER's performance predictions — confinement scaling, D-T operations experience, remote maintenance — was written at JET.