Joint European Torus's swansong yields fusion record

The Joint European Torus (JET) has bowed out with a final hurrah by setting a world record in energy output.

The UK-based JET began operation in 1983, and the results announced yesterday represent the facility's swansong as it transitions into repurposing and decommissioning.

In its final deuterium-tritium experiments, JET produced high fusion power for five seconds, "resulting in a ground-breaking record of 69 megajoules using a mere 0.2 milligrams of fuel."

JET was one of the world's largest and most powerful fusion machines. It was a tokamak, using magnetic fields to contain plasma in the shape of a doughnut. Its first deuterium-tritium experiments took place in 1997, and it previously set a record in 2021 by producing 59 megajoules during a five-second pulse.

However, JET's days have been numbered for some time. The enormous ITER facility is expected to produce its first plasma in 2025, based on 2016's baseline schedule, and reach full magnet power in 2026. In the latter part of its operational life, JET's carbon inner wall was replaced with one made of the metals beryllium and tungsten, dubbed the ITER Like Wall (ILW) as part of upgrades aimed at making JET's configuration as close to ITER as possible.

The changes meant that scientists were able to model experiments planned for ITER.

A petition was set up to keep JET operational until ITER came online but, alas, managers at EUROfusion pointed out that the time for considering ways of keep JET running had passed, and the decommissioning process was already underway.

Dr Pietro Barabaschi, ITER director-general, said: "Throughout its lifecycle, JET has been remarkably helpful as a precursor to ITER: in the testing of new materials, in the development of innovative new components, and nowhere more than in the generation of scientific data from Deuterium-Tritium fusion.

"The results obtained here will directly and positively impact ITER, validating the way forward and enabling us to progress faster toward our performance goals."

Faster progress would be most welcome. ITER has been dogged by schedule delays during its design and construction. The current 2025 date for first plasma was originally expected years earlier, and the start of deuterium-tritium operation is not expected until 2035.

As well as ITER, research carried out at JET will also benefit other fusion projects, including the UK's STEP prototype powerplant and Europe's demonstration powerplant, DEMO. ®