20th February 2025 New world record for nuclear fusion The WEST tokamak in France has maintained plasma for 1,337 seconds, a new world record duration for nuclear fusion and 25% longer than a similar effort by China last month.
France's Atomic Energy Commission (CEA) has announced a major milestone achieved by the WEST tokamak, a nuclear fusion experiment operating in the southeast of the country. On 12th February, the machine sustained a continuous plasma for 1,337 seconds (over 22 minutes). In doing so, it smashed the previous record for plasma duration achieved with a tokamak. The plasma reached a temperature of 50 million degrees Celsius, which is more than three times hotter than the centre of the Sun. While the fusion reaction did not produce a net energy gain, sustaining plasma for extended periods is crucial for the development of future reactors, such as the ITER, which is scheduled for first plasma in 2034. Longer durations allow scientists to refine plasma stability, assess the resilience of reactor components, and improve heating and confinement techniques – all vital to achieving a practical and continuous fusion energy source. "WEST has achieved a key technological milestone by maintaining hydrogen plasma for more than 20 minutes through the injection of 2 MW of heating power," said Anne-Isabelle Etienvre, Director of Fundamental Research at CEA. "Experiments will continue with increased power. This excellent result allows both WEST and the French community to lead the way for the future use of ITER."
WEST, which stands for Tungsten (chemical symbol "W") Environment in Steady-State Tokamak, has a long history of plasma research. Originally known as the Tore Supra, the machine first became operational in 1988. It set an early world record in 2003, sustaining plasma for 6 minutes and 30 seconds while injecting and extracting over 1,000 megajoules of energy. This record stood for 18 years until 2021, when China's Experimental Advanced Superconducting Tokamak (EAST) surpassed it by sustaining plasma for 1,056 seconds (17 minutes and 36 seconds). In 2016, the CEA performed an extensive upgrade of the Tore Supra and rebranded it as WEST. The upgrade included tungsten walls and actively cooled components designed to withstand extreme plasma conditions. Over the past decade, WEST has conducted more than 10,000 tests, refining its ability to sustain long-duration plasmas. In January 2025, EAST briefly extended its own record, sustaining plasma for 1,066 seconds. Just weeks later, however, WEST surpassed this milestone, with its new world record of 1,337 seconds – a 25% improvement over EAST's latest effort. In the coming months, the WEST team will accelerate their efforts to achieve long plasma durations – potentially up to several hours combined – but also to heat the plasma to even higher temperatures, with a view to approaching the conditions needed for self-sustaining fusion reactions similar to those expected in future commercial reactors. WEST is just one part of an international effort comprising other major experiments in which CEA researchers have been heavily involved. These projects include JET in the UK (which generated a world record 69 megajoules in October 2023), JT-60SA in Japan, EAST in China, and KSTAR in South Korea, not to mention the upcoming flagship machine that is ITER.
Background image: Christopher Roux, EUROfusion, CC BY 4.0, via Wikimedia Commons
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