Wedoany.com Report-Jun 5, Germany’s Wendelstein 7-X, the world’s largest stellarator-type fusion device, achieved a world record for the triple product, a key fusion physics parameter, during its latest experimental campaign, which concluded on May 22, 2025, in Greifswald. The triple product, calculated by multiplying fuel density, fuel temperature, and confinement time, reached a new peak for long plasma durations, surpassing previous tokamak records for extended pulses.

Inside the vacuum vessel of Wendelstein 7-X

The Max Planck Institute for Plasma Physics (IPP) in Greifswald, in collaboration with researchers from Europe and the United States, facilitated this milestone. A critical component was a new pellet injector, developed by the U.S. Department of Energy’s Oak Ridge National Laboratory, which injected approximately 90 frozen hydrogen pellets, each about a millimeter in size, over 43 seconds. This allowed continuous plasma refueling, enabling a plasma duration of 43 seconds at temperatures exceeding 20 million degrees Celsius, with peaks reaching 30 million degrees.

Thomas Klinger, head of operations at Wendelstein 7-X and head of stellarator dynamics and transport at IPP, stated: “The new record is a tremendous achievement by the international team. It impressively demonstrates the potential of Wendelstein 7-X. Elevating the triple product to tokamak levels during long plasma pulses marks another important milestone on the way toward a power-plant-capable stellarator.”

The experiment utilized precise coordination between powerful microwave heating and variable pulse rates from the pellet injector, a technique vital for future fusion reactors. Diagnostic tools, including an X-ray spectrometer from Princeton Plasma Physics Laboratory for ion temperature measurements and IPP’s unique interferometer for electron density data, were essential in calculating the triple product. The energy confinement time was also determined using IPP-developed diagnostics.

The campaign increased energy turnover to 1.8 gigajoules over six minutes, surpassing the previous record of 1.3 gigajoules set in February 2023. Unlike tokamak reactors, such as the Joint European Torus in the UK or the ITER project in France, the Wendelstein 7-X stellarator employs a figure-8 design to address magnetic confinement challenges, enabling continuous operation potential without auxiliary equipment.

While not designed to produce energy, Wendelstein 7-X aims to validate stellarators as viable power plant candidates. This record underscores the device’s capability to sustain long plasma durations, advancing fusion research and supporting the development of sustainable energy solutions through international collaboration.