JET Tokamak's Latest Fusion Energy Record

The result came as part of an experimental campaign to verify operating scenarios for future fusion machines, under conditions as close as possible to those in ITER and future fusion power plants. The result was made possible through the dedication of the international team of scientists and engineers at JET and reflects the central role that JET has played in accelerating the development of fusion energy.

Deuterium-Tritium campaign

In September 2023, the EUROfusion consortium of fusion laboratories around Europe, including Switzerland, started an ambitious experimental campaign at the JET facility of the UK Atomic Energy Authority (UKAEA) in Culham, UK. Their goal: to test out operating scenarios extrapolated from small and medium size European devices to pave the way for the international ITER project and the fusion power plants to follow. JET is unique amongst present-day tokamak machines—which trap a cloud of hot, ionised fuel, in the plasma state, in a donut-shaped cage of magnetic fields—for its capability to work with the deuterium-tritium fuel that will form the basis of future fusion machines like ITER and the demonstration power plant DEMO.

Reproducible energy record

Using advanced scenarios to structure and control their plasma, the researchers set a new fusion energy record of 69.26 megajoules of heat released during a single pulse in JET. Released over six seconds from only 0.21 milligrams of fuel, the energy record equals the energy released from burning 2 kilograms of coal. The JET record is 20 times the amount of energy released in a recent shot at the U.S. National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in October 2023, which used a different approach to fusion to produce more energy than was absorbed by the fuel pellet. The new achievement by the EUROfusion team breaks their previous world records of 59 megajoules (2022) and 22.7 megajoules (1997), which were also set at JET. The scientists at JET were able to reliably reproduce the necessary fusion conditions for the new record in multiple experimental pulses, demonstrating the understanding and control they have achieved over the complex fusion processes.

Testing operating scenarios for ITER

The shots that broke JET’s previous fusion energy record came as a late addition to JET’s third and final run of deuterium-tritium experiments. The campaign was primarily designed as the first-ever opportunity to demonstrate that crucial operating scenarios for ITER will work in a deuterium-tritium environment with its abundant fusion reactions. “Perhaps even more interesting to me than the record is what we have achieved in terms of operating scenarios for ITER”, says the Head of EUROfusion’s Tokamak Exploitation Task Force, Emmanuel Joffrin from the French EUROfusion member CEA. “Not only did we demonstrate how to soften the harsh heat flowing from the plasma to the exhaust, we also showed in JET how we can get the plasma edge into a stable state thus preventing bursts of energy reaching the wall. Both techniques are intended to protect the integrity of the walls of future machines. This is the first time that we’ve ever been able to test those scenarios in a deuterium-tritium environment.” Dedicated upgrades over the past decade have brought JET’s technical specifications as close as possible to those of ITER, allowing for studies that will enable that future machine to hit the ground running when it enters operation. Dr Fernanda Rimini, JET Senior Exploitation Manager, JET Scientific Operations Leader, said:

We can reliably create fusion plasmas using the same fuel mixture to be used by commercial fusion energy powerplants, showcasing the advanced expertise developed over time.

Most approaches to creating commercial fusion favour the use of two hydrogen variants – deuterium and tritium. When deuterium and tritium fuse together they produce helium and release vast amounts of energy – a reaction that will form the basis of future fusion powerplants. Professor Ambrogio Fasoli, Direstor of Swiss Plasma Center and Programme Manager (CEO) at EUROfusion, said:

Our successful demonstration of operational scenarios for future fusion machines like ITER and DEMO, validated by the new energy record, instil greater confidence in the development of fusion energy. Beyond setting a new record, we achieved things we’ve never done before and deepened our understanding of fusion physics.

Andrew Bowie, UK Minister for Nuclear and Networks, said:

JET’s final fusion experiment is a fitting swansong after all the groundbreaking work that has gone into the project since 1983. We are closer to fusion energy than ever before thanks to the international team of scientists and engineers in Oxfordshire. The work doesn’t stop here. Our Fusion Futures programme has committed £650 million to invest in research and facilities, cementing the UK’s position as a global fusion hub.

Professor Sir Ian Chapman, UKAEA CEO, said:

JET has operated as close to powerplant conditions as is possible with today’s facilities, and its legacy will be pervasive in all future powerplants. It has a critical role in bringing us closer to a safe and sustainable future.

JET concluded its scientific operations at the end of December 2023. The findings of JET’s research have critical implications not only for ITER—the fusion research mega-project being built in the south of France—but also for the UK’s STEP prototype powerplant, Europe’s demonstration powerplant, DEMO, and other global fusion projects, pursuing a future of safe, low-carbon, and sustainable energy. 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 once operation begins. On a personal note, it has been for me a great privilege having myself been at JET for a few years. There I had the opportunity to learn from many exceptional people.