JET Fusion Reactor Sets World Record in Final Tests

8 February 2024

The Joint European Torus (JET) has demonstrated that magnetic fusion is suitable for reliably generating energy. In the last experiment campaign, which involved scientists from Forschungszentrum Jülich, EUROfusion researchers also set a new world record. On 3 October, they generated a five-second pulse with an energy of 69 megajoules. The results represent an important milestone for fusion technology and will play a key role in the launch of JET's successor, ITER, which aims to demonstrate the feasibility of fusion energy on an industrial scale.

Fusion energy makes use of the same reactions that power the sun and stars. The Joint European Torus (JET), which brought its scientific operations to a close at the end of last year, is the largest and most powerful fusion experiment to date and the central research facility of the European fusion programme. The facility has been used jointly by more than 31 European research institutions since 1983.

JET was designed as a tokamak, which uses strong magnetic fields to confine a plasma in a doughnut shape. JET can already produce similar conditions to its successor ITER and is the only tokamak in the world that can be operated with the same deuterium-tritium fuel mixture that is planned for ITER and subsequent facilities.

Deuterium and tritium are two heavier forms of hydrogen and together offer the highest reactivity of all fusion fuels. At a temperature of 150 million degrees Celsius, deuterium and tritium fuse to form helium and release an enormous amount of heat energy without producing greenhouse gases. Nuclear fusion also has the advantage that it is inherently safe. It cannot set off any uncontrollable chain reactions and does not produce any long-lived waste.

Fusion experts from Forschungszentrum Jülich have been involved in JET since its beginnings over 40 years ago. They were responsible for the design and construction of the divertor. This is the only part of the tokamak reactor that comes into direct contact with the hot fuel and has to withstand more intense conditions than spacecraft upon re-entering the Earth's atmosphere.

As part of the final experiment campaign, the Jülich researchers investigated control techniques to protect the reactor walls and conducted active laser measurements for the first time in connection with the recovery of the tritium absorbed in the walls. The efficient recycling of this fusion fuel is essential for the operation of fusion plants and their decommissioning at the end of their service life.