This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Future fusion power plants aim to recreate the heart of a star here on Earth to power our future energy needs. While the core fusion plasma will burn at hundreds of millions of degrees, the surrounding structural components must handle sudden, punishing heat loads that rival the extreme temperatures faced by spacecraft upon reentry into Earth's atmosphere.
Copper and its alloys are primary candidates for handling these intense heat fluctuations, making it vital to understand exactly how the metal behaves when pushed to its melting point. Now, researchers at the Department of Energy's SLAC National Accelerator Laboratory and collaborators have captured a detailed, step-by-step look at copper atoms as they underwent extreme heating. Published in Nature Communications, the results revealed a key parameter that allowed copper's crystal lattice to melt steadily rather than collapse instantaneously, as earlier simulations predicted.
"These results greatly improve the simulations we use to predict which materials have the best shot at surviving the extreme conditions of future fusion reaction chambers," said Mianzhen Mo, a SLAC staff scientist who led the research. "They also demonstrate the incredible, atomic-scale resolution imaging we can achieve at SLAC's electron camera." In the search for resilient materials, knowing the temperature at which a material melts isn't enough. Materials in future fusion energy chambers will undergo transient thermal heating—a swift scorching that pushes atomic bonds to the limit, supercharges energy flow across underlying crystal structures and causes otherwise well-understood materials to behave in unusual ways.
Researchers use computer simulations, aided by AI and machine learning, to sift through innumerable combinations of elements and identify promising candidate materials for real-world testing. In recent years, Mo's group has investigated the properties of tungsten after it was flagged as a potential material for fusion chambers. Leading models suggest that copper alloys could serve as "heat sinks"—materials that cool fusion systems by absorbing heat from materials closer to the fusion reactions.
Mo's team decided to take a closer look, starting with a pure copper sample. To test the resilience of fusion-chamber candidate materials, researchers often use a "cook and look" approach, first zapping a sample material with extreme heat, then examining the fully baked aftermath. Whether the copper melts slowly or suddenly collapses, by the time the researchers look, the sample resembles nothing more than a metallic brown puddle.
"We needed a time-resolved, step-by-step look at the melting process," Mo said. The team brought their sample to MeV-UED, SLAC's powerful electron camera that captures atomic and molecular movements down to the femtosecond—a millionth of a billionth of a second. They blasted a thin copper film with laser heat, then sent an electron beam to image the sample as it heated.
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