Kernfusion mit Wendelstein 7-X | Thomas Klinger | GDNÄ 2026

Summary

Thomas Klinger explains the physics behind fusion energy and the role of the Wendelstein 7-X stellarator. Fusion joins light atomic nuclei, unlike fission, which splits heavy nuclei. The most practical fusion reaction discussed is deuterium–tritium (D–T): the nuclei fuse to form helium and a neutron, releasing energy as mass is converted into kinetic energy. The reaction releases energy overall, though the fuel must first be heated and confined to initiate fusion.

The Sun produces energy through the proton–proton chain, which relies on its immense gravity to confine an extremely dense, hot core. That approach cannot be reproduced on Earth. Magnetic-confinement fusion instead uses a much thinner plasma heated to around 100–200 million degrees. Because the plasma consists of charged particles, magnetic fields can guide it and keep it away from the vessel walls.

A major challenge is maintaining high plasma pressure and good thermal insulation for long periods. Turbulence creates vortices that carry heat and particles outward, making confinement harder. The stellarator’s specially shaped magnetic field is designed to improve confinement and support steady operation.

How Wendelstein 7-X works and what it has demonstrated

• Magnetic configuration: Computer calculations were used to optimize the magnetic-field shape. The field is produced by 50 superconducting coils of five different designs, with additional planar coils available for adjustments.
• Vacuum vessel and cooling: The plasma sits in an evacuated vessel with water-cooled, heat-resistant wall components. The superconducting magnets are cooled to about 3.4 kelvin and enclosed in a separate vacuum vessel.
• Plasma heating and observation: Microwaves heat the gas, while diagnostic systems monitor the plasma. In one example, the plasma reached about 25 million degrees Celsius.
• Increasing plasma density: Frozen hydrogen pellets about 1 mm across were fired into the plasma. A run using 20 pellets increased the plasma’s density and energy. In a longer experiment, 100 pellets were used, and the plasma was maintained at about 20 million degrees for 43 seconds.
• Long-pulse operation: Klinger describes a 500-second plasma run as progress toward the sustained operation a power plant would require. Technical problems, including failing microwave tubes, remained.
• Managing heat at the wall: The talk describes “detachment,” in which a radiation belt forms around the plasma and reduces the heat load on the wall.

Wendelstein 7-X is an experimental facility, not a power plant. Its purpose is to test the stellarator’s magnetic-field concept and demonstrate sustained operation. A future power plant would need a much larger plasma volume and would have to combine strong confinement with long-duration operation.

The proposed fuel cycle would use deuterium and tritium. Deuterium is available in water, while tritium is radioactive and has a half-life of about 12.3 years, so it would need to be produced in the reactor using lithium and fusion neutrons. Those neutrons would also heat the reactor’s wall; a coolant could carry that heat to a steam-generation system.

Klinger presents fusion as a possible complement to renewable energy, particularly for large-scale electricity generation and industrial heat. He notes that fusion would still involve radiation protection and some activated materials, but describes it as producing no high-level radioactive waste and having a passively safe plasma that stops if operating conditions fail. These are potential advantages, not evidence that fusion is already commercially available.

Researchers and sources featured

• Thomas Klinger — speaker and fusion researcher.
• Wendelstein 7-X — the stellarator experiment discussed.
• No other researchers or external sources are named in the subtitles.