Breaking New Ground: JET Tokamak’s Latest Fusion Energy Record Shows Mastery of Fusion Processes

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 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 donut-shaped cloud of hot, ionised fuel or plasma in a 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, 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.”

UK Minister for Nuclear and Networks, Andrew Bowie, 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.”

40 years of fusion science

JET has been the largest and most successful fusion experiment in the world, and a central research facility of the European Fusion Programme. The machine is based at the UKAEA campus in Culham, UK and has been a collective facility used by European fusion researchers under the management of the EUROfusion consortium—experts, students, and staff from across Europe and internationally, co-funded by the European Commission. A big aspect of its success was to show that large scientific projects can be done in a collaborative way on a global scale. Since its inception in 1983 as a joint European project, JET has been at the forefront of groundbreaking achievements, spearheading the pursuit of safe, low-carbon, and sustainable fusion energy solutions to meet the world’s future energy demands. Over its lifetime JET has delivered crucial insights into the complex mechanics of fusion, allowing scientists to plan the international fusion experiment ITER and DEMO, the demonstration fusion power plant currently under design by the European fusion community. Built by Europe and used collaboratively by European researchers over its lifetime, JET became UKAEA property in October 2021. The machine celebrated its 40th anniversary in June this year, and ceased plasma operations at the end of 2023, having created 105,842 pulses.

Fusion energy’s potential

Fusion, the process that powers stars like our sun, promises a clean baseload source of heat and electricity for the long term, using small amounts of fuel that can be sourced worldwide from inexpensive materials. Deuterium and tritium are two heavier variants of ordinary hydrogen and together offer the highest reactivity of all fusion fuels. At a temperature of 150 million degrees Celsius, deuterium and tritium fuse together to form helium and release a tremendous amount of heat energy without any greenhouse contributions. Fusion is inherently safe in that it cannot start a run-away process and produces no long-lived waste.