The Joint European Torus has sustained a super-hot plasma for 5 seconds, producing 59 megajoules of energy and suggesting that larger experiments could produce more power than is put in
A white hot river of heat winds around the bottom of a doughnut-shaped machine before the searing light jumps up to fill the space and vanishes, leaving only darkness. This is the moment when a European experiment to reproduce the process powering the sun, called fusion power, set a new global energy record.
The experiment at the Joint European Torus (JET) in Oxford on 21 December saw a super-hot plasma sustained for 5 seconds, producing a record 59 megajoules of heat energy. JET’s previous record was 22 megajoules for less than a second, set in 1997.
“It’s not an unexpected result. It is really the pinnacle of the work that is done for years: that yes, it does do what you understood it should do. I feel a certain amount of relief,” says team member Volker Naulin at EuroFusion, a consortium of fusion research groups. Nuclear fusion holds the promise of a continuous low carbon power supply without the radioactive waste problem of its cousin, nuclear power from fission.
The new record is significant as it indicates commercial fusion power could become a reality. While 5 seconds might not sound like long, it is the maximum JET’s copper magnets can manage. Naulin says the duration and output shows that our understanding of plasma physics is settled. The achievement suggests a far bigger and more powerful fusion tokomak machine being built in the south of France, called ITER, should achieve its goals when it is switched on in 2025.
Those aims are to generate more power than is put in, the long-awaited goal of fusion power, and to do so for a sustained period of time, about 50 minutes initially. Naulin says JET’s new record is a sign that the modelling for ITER is correct. “It’s really confirmation that what has been calculated for ITER is not a fantasy number.”
The big technology change that enabled the new record was a shift away from carbon-based materials in the wall of JET, such as graphite, which act as a sponge for the hydrogen isotopes used to create the plasma. Instead, metals such as tungsten and beryllium were used in the wall, similar to those that will be used for ITER.
The record came after a series of plasma “shots” generated at JET between September and December, which had been delayed by around a year due to the pandemic. The fusion attempts were the first at JET in more than two decades to use two types of hydrogen isotope, deuterium and tritium. Most tests in recent years have used only deuterium. Using them both together can achieve fusion at lower temperatures, and is considered by fusion researchers to be the most efficient fuel for a future power station.
Juan Matthews at the University of Manchester, UK, says the scale of the new record set at JET means it is “much more significant” than an attempt last August at a US facility using lasers and an entirely different approach to creating fusion.
“JET is getting close to breakeven, with power close to that being used to run the reactor,” he says. “We must remember that JET is using real fuel with tritium as well as deuterium and these pulsed tests will be valuable in making sure ITER is able to get off to a running start once it begins operation. Very few fusion experiments are using tritium.”
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