Highest energy output achieved using nuclear fusion

The highest energy output generated using nuclear fusion is 59 megajoules, achieved during a test at the Joint European Torus (JET) on 21 December 2021. The test saw JET generate power at a rate of 11 megawatts for five seconds. JET is located at the Culham Centre for Fusion Energy in Oxfordshire, UK, and funded by the EUROfusion consortium.

The test used a fuel mixture of deuterium and tritium, two isotopes of hydrogen that, when fused, form a helium nucleus (an alpha particle) and single high-energy neutron. This is the fuel that scientists believe will enable sustainable power generation from nuclear fusion. The full-power fusion test of 21 December was important because it allowed researchers to confirm a number of predictions that had been made as part of the design of JET's replacement, the International Thermonuclear Experimental Reactor (or ITER) which is currently under construction in Provence, France.

JET was built in 1983, and is the largest (weighing 2,800 tonnes) and most powerful example of a type of fusion reactor called a tokamak. This design uses powerful magnetic fields to contain superheated plasm (at temperatures of up to 150 million kelvin) in a doughnut-shaped chamber. It set the previous record in 1997, when another deuterium-tritium test generated 21.7 megajoules of energy in a short burst. Since that landmark test, JET has mostly been running on deuterium alone – which simplifies maintenance and operations, allowing regular experiments to verify predictions about the behaviour of high-temperature plasma. On 19 January 2022, it was announced that JET had performed its 100,000th experimental pulse.