Graphene nanoribbon explored as basis for gamma monitoring in fusion machines

A tiny ribbon may hold big promise for detecting radiation damage in future tokamaks.

Researchers at the University of Arizona have shown that, when exposed to gamma radiation, graphene nanoribbons exhibit altered current flow from quantum effects while maintaining their atomic framework, suggesting strong potential for use in sensors for monitoring gamma-induced damage to materials and devices in extreme environments, such as fusion machines.

How it works: For a study published in ACS Applied Materials & Interfaces, the researchers fabricated graphene ribbons that were nine atoms wide, one atom thick, and about 45 nanometers long. The ribbons were exposed to gamma radiation from a cobalt-60 source. The researchers tested three exposure lengths-180 minutes, nearly 7 hours, and over 18 hours-after which their structures were reassessed.

"The devices survive the exposure and still respond, but their electrical performance changes dramatically," said Zafer Mutlu, assistant professor of materials science and engineering at the University of Arizona. "That's exactly the behavior we want from a sensor."

According to a university press release, the gamma radiation appears to "subtly alter the ribbon edges," triggering a phenomenon called Anderson localization, "which traps charge-carrying electrons in place and sharply reduces current."

Mutlu sees this as a strong foundation for a sensor that could be placed inside the first wall of a fusion machine. If it works, the sensors could provide direct measurements of radiation-induced degradation, which is currently measured only indirectly through sensors placed outside the first wall.

The aim is to identify signs of radiation-related degradation before failure occurs. The press release said this type of sensor could reduce costly inspection and maintenance shutdowns.

"Real-time monitoring is our vision for this project," Mutlu said.

Next steps: More testing is required to examine the graphene nanoribbon's behavior under different radiation doses. The team also plans to explore ribbons of different sizes, aiming to optimize the device according to the desired application, which could also include other environments where radiation monitoring is critical, such as deep space.

"You can design the material atom by atom, molecule by molecule," said Mutlu. "You can make it less sensitive, more sensitive, non-sensitive."