An international collaboration of researchers at the United Kingdom Atomic Energy Authority’s (UKAEA) MAST Upgrade facility has successfully demonstrated an innovative exhaust system capable of reducing the extreme heat loads within a fusion reactor by over ten times compared to conventional designs. This pivotal development directly addresses one of the most significant engineering hurdles to the realization of commercial fusion power plants.

Future fusion power plants, such as tokamaks, must contain plasma—a superheated gas of hydrogen isotopes—at temperatures exceeding 100 million degrees Celsius, far hotter than the sun's core, to initiate and sustain fusion reactions. The component responsible for managing the exhaust of this super-hot plasma, known as the divertor, must endure an incredible onslaught of heat and charged particles. Its ability to withstand these conditions is paramount for the long-term operational viability of fusion energy.

The new ‘Super-X’ divertor design, developed and tested at UKAEA's purpose-built MAST Upgrade facility, offers a robust solution. This system features a significantly longer, extended exhaust path, often referred to as 'long legs.' This extended path provides the searing plasma with increased volume and time to cool down before it makes contact with any solid surface, thereby drastically reducing the thermal load and stress on the reactor walls. "These exciting results were made possible by strong international collaborations between the UKAEA, TU Eindhoven, DIFFER and EUROfusion teams that will continue pushing the boundaries of our understanding in this important area of research," stated James Harrison, head of MAST Upgrade Science, UKAEA.

The latest findings elevate the Super-X concept from a theoretical promise to a proven technology. Crucially, researchers confirmed that the Super-X approach enables exhaust control without negatively impacting the opposing divertor or the core plasma where fusion energy is generated. This independent management of the plasma edge, without disrupting the stability of the fusion core, is vital for a continuously operating and stable power plant. Bob Kool, representing DIFFER and TU/e, concluded that "These results clearly demonstrate the many benefits that alternative divertors can offer in maintaining acceptable divertor conditions in fusion power plants."

Furthermore, the Super-X design has proven to be significantly easier to manage than traditional, short-legged divertors. The research, published in the Nature journal, suggests that even modest design modifications can yield substantial benefits, offering engineers greater flexibility in balancing performance with engineering complexity for future reactor designs. This advancement in heat management is a key area of global fusion research, complementing other efforts like the DIII-D National Fusion Facility's investigation into 'negative triangularity' plasma configurations for high confinement and divertor detachment.