Wendelstein 7-X sets new fusion record

Summary

The Wendelstein 7-X nuclear fusion research reactor in Greifswald has reported a new record. The Max Planck Institute for Plasma Physics (IPP), which operates the reactor, announced that a world record for the so-called triple product in long plasma discharges had been achieved at the research facility during the current experimental campaign. A new peak value was achieved over a plasma duration of 43 seconds. This was achieved on May 22, 2025, the last day of the OP 2.3 experimental campaign. The triple product is the decisive factor in nuclear fusion. It is calculated from the particle density of the plasma, the temperature of the ions between which fusion reactions take place, and the energy confinement time. This is the time over which the thermal energy escapes from the plasma if it is not reheated. Only when a certain threshold value is reached does the fusion reaction become self-sustaining without the need for further heating. A positive energy balance is then achieved, i.e. the plasma generates more fusion power than the heat input. New pellet injector used During the record-breaking run, around 90 fuel pellets were injected into the reactor over 43 seconds. At the same time, powerful microwaves heated the plasma to over 20 million degrees Celsius, and even to 30 million degrees Celsius at peak times. To achieve an optimum combination of heating power and fuel filling, heating and pellet injection must be very precisely coordinated. A new type of pellet injector developed at the US Department of Energy's Oak Ridge National Laboratory in Tennessee was used for this purpose. This system shoots the pellets – millimeter-sized balls of frozen hydrogen – into the reactor. The pellet injector was operated for the first time in such a way that it ran at different predefined pulse rates. This scheme can also be extended to longer plasma durations of several minutes, which is important for future fusion reactors. The record is a great achievement by the international...