10x cut in fusion reactor heat could be achieved with Super-X exhaust’s long ‘legs’

An international team of researchers at the UK’s MAST Upgrade facility has successfully tested an innovative exhaust system that can reduce the immense heat loads inside a fusion reactor by more than ten times compared to previous designs.

“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,” said James Harrison, head of MAST Upgrade Science, UKAEA. 

This crucial development directly tackles one of the most significant obstacles to building commercial fusion power plants.

Future fusion power plants will operate under extreme conditions. To generate energy, they must contain plasma—a superheated gas of hydrogen fuel—hotter than the sun.

“Temperatures of over 10,000 degrees Celsius (18,032°F) and a hail of charged particles from the fusion fuel (plasma): these are extreme conditions that the exhaust wall (divertor) of future fusion power plants will need to withstand,” stated the researchers in a press release.

The component responsible for this, the divertor, must withstand this incredible onslaught, making its design a critical engineering challenge for the viability of fusion power.

Solving the issue with longer “legs”

The new ‘Super-X’ divertor design offers a solution. Developed at the United Kingdom Atomic Energy Authority’s (UKAEA) purpose-built MAST Upgrade facility, this system features a longer, extended exhaust path. 

These longer “legs” give the searing plasma more room and time to cool before it ever touches a solid surface, drastically reducing the heat and stress on the reactor walls.

“Demonstrating that the plasma conditions in the divertors of MAST Upgrade can be controlled independently is an important advancement towards developing robust control of plasma exhaust in future machines,” highlighted Harrison. 

The latest results move the Super-X concept from a promising theory to a proven technology. 

“The new results are a world-first: at MAST Upgrade, the researchers have shown that the Super-X approach enables exhaust control without impacting the opposing divertor or the core of the plasma where fusion energy is produced,” added the press result.

This ability to manage the edge without disrupting the core is vital for a stable, continuously operating power plant.

Easier to manage

Researchers also confirmed that the Super-X design is significantly easier to manage than conventional, short-legged divertors. 

The findings even suggest that modest design modifications can yield substantial benefits, offering engineers flexibility in designing future reactors by balancing performance with engineering complexity.

“These results clearly demonstrate the many benefits that alternative divertors can offer in maintaining acceptable divertor conditions in fusion power plants,” concluded Bob Kool for DIFFER and TU/e.

Heat management has become a key area of research in the field of nuclear fusion energy. Several researchers across the globe are working towards it.

Recently, in another development, scientists at the DIII-D National Fusion Facility investigated a different approach to tokamak operation. 

Their experiments demonstrated that a plasma configuration known as “negative triangularity” can achieve the high-performance conditions necessary for sustained fusion energy. This was the first time when researchers operating with a negative triangularity shape achieved high plasma confinement in conjunction with “divertor detachment.”

The research has been published in the Nature journal.