On May 22, 2025, the Wendelstein 7-X (W7-X) stellarator at the Max Planck Institute for Plasma Physics (IPP) in Greifswald concluded its latest experimental campaign with a major success: a new world record in the triple product for long plasma durations, a key milestone in nuclear fusion research. This result confirms the stellarator’s potential as a viable path toward future fusion power plants.
The triple product – the fusion key parameter combining plasma density, temperature, and energy confinement time – was maintained at a record level for 43 seconds. W7-X now surpasses all previous long-duration results from tokamak devices, including those from JT60U (Japan) and JET (UK).
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| In a future fusion power plant, a plasma with a high triple product (y-axis, logarithmic scale) must be maintained for long periods (x-axis). Previous fusion experiments only achieved high values for plasma durations of a very few seconds. On May 22, 2025, Wendelstein 7-X achieved the world record for plasma times of more than 30 seconds with a high fusion product. In this OP2.3 experiment campaign, further best values were achieved for plasma durations between 30 and 40 seconds. Tokamaks remain the record holders for short plasma times. Source: MPI for Plasma Physics, Dinklage et al (to be published) / X. Litaudon et al 2024 Nucl. Fusion 64 015001 |
This breakthrough was made possible by international collaboration, especially with the U.S. Department of Energy’s Oak Ridge National Laboratory, which developed and delivered a novel pellet injector. During the record-setting discharge, around 90 frozen hydrogen pellets were injected into the plasma, enabling continuous refueling. Simultaneous microwave heating raised the plasma temperature above 20 million degrees Celsius, peaking at 30 million degrees.
Crucial diagnostic data came from Princeton Plasma Physics Laboratory and IPP, enabling precise calculation of the triple product.
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| The pellet injector in the Wendelstein 7-X experimental hall. Photo: MPI for Plasma Physics, Beate Kemnitz |
In addition to the new triple product record, W7-X achieved two further milestones:
- A new energy turnover record of 1.8 gigajoules (360 seconds plasma duration), exceeding the previous 1.3 GJ record and even surpassing values from the 1000-second EAST tokamak experiment.
- For the first time, plasma pressure reached 3% of magnetic pressure across the entire plasma volume, an important benchmark on the way to achieving reactor-relevant conditions (4-5%).
"The records of this experimental campaign are much more than mere numbers. They represent a significant step forward in validating the stellarator concept – made possible through outstanding international collaboration," said Prof. Dr. Robert Wolf, Head of Stellarator Heating and Optimization at IPP.
Wendelstein 7-X is operated in cooperation with EUROfusion and aims to demonstrate that stellarators can achieve the confinement quality needed for a future fusion power plant - safely, continuously, and efficiently.
Since the start of Wendelstein 7-X operation in 2015, a research team from the Institute of Plasma Physics and Laser Microfusion (IPPLM) in Poland has been actively participating in the device’s experimental campaigns. Members of the team operating the PHA (pulse-height analyzer) diagnostic system, designed and built by IPPLM researchers, were also involved in the record-setting experiment.
More information: www.ipp.mpg.de/5532945/w7x
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| View inside the vacuum vessel of Wendelstein 7-X in Greifswald. Photo: MPI for Plasma Physics, Jan Hosan |
