In the quest to harness nuclear fusion as a nearly limitless and clean energy source, researchers have turned to an unlikely tool — mayonnaise. This household condiment is helping scientists at Lehigh University understand complex fluid dynamics that occur during fusion reactions, potentially paving the way for more efficient fusion processes.

The nuclear fusion dream

Nuclear fusion is the process that powers the sun and could change the world’s energy landscape forever. Achieving fusion on Earth, however, involves replicating the sun’s extreme conditions, a feat that remains extremely challenging.

In late 2022, physicists at the National Ignition Facility (NIF) in California announced a landmark achievement in nuclear fusion. For the first time, they had successfully extracted more energy from a controlled fusion reaction than was used to initiate it. On October 30, 2023, the NIF set a new record for laser energy. For the first time, they fired 2.2 MJ of energy on an ignition target, resulting in 3.4 MJ of fusion energy yield.

The announcement led to a familiar divide. Fusion enthusiasts celebrated it as a sign that the long-awaited fusion era might be nearing. Skeptics, however, remained unconvinced, pointing out that fusion has been “20 years away” for decades. This tension underscores the high stakes involved.

The world is in desperate need of a clean, abundant energy source to replace fossil fuels and mitigate the climate crisis. Fusion, which merges light atomic nuclei to release energy, has always been this sort of white whale. But after decades of research, it is still not clear when — or if — fusion will be a significant contributor to our energy mix.

Most projections suggest that practical fusion energy might not be realized until around 2050. This timeline means that fusion is unlikely to play a significant role in reducing carbon emissions by mid-century — a crucial period for addressing global warming.

Harnessing nuclear fusion

The challenges of harnessing fusion are immense. The process involves creating and maintaining conditions similar to those inside stars, with temperatures reaching 100 million kelvins. This requires confining a plasma of hydrogen isotopes, deuterium, and tritium, within powerful magnetic fields. And this task has proven exceedingly difficult. Moreover, fusion reactors must withstand the intense neutron bombardment generated during the reactions, which degrades materials over time.

There are multiple designs for fusion reactors currently in development, but the most promising are inertial confinement fusion and magnetic confinement fusion. The former is what the INF used, an approach where scientists use powerful lasers or ion beams to compress a tiny pellet of fuel — typically a mix of deuterium and tritium — until the conditions for fusion are met.

An example of magnetic confinement fusion is the International Thermonuclear Experimental Reactor (ITER) in France, which has recently been delayed until 2039 rather than 2035 with an extra cost of $5 billion. This method relies on powerful magnetic fields to contain a superheated plasma — an ionized gas where fusion occurs. The plasma, reaching temperatures ten times hotter than the sun’s core, is confined within a doughnut-shaped vacuum chamber known as a tokamak. The magnetic fields prevent the plasma from touching the chamber walls, which would cool it down and stop the reaction.

Mayo and nuclear fusion physics

Okay, so where does mayo fit into all of this? A major hurdle to stable nuclear fusion using inertial confinement is the Rayleigh-Taylor instability. This is a phenomenon that occurs when different-density materials are subjected to opposing gradients of density and pressure, leading to unpredictable and often detrimental outcomes during the fusion process.

To tackle this, Arindam Banerjee, a professor of mechanical engineering at Lehigh University, and his team have turned to an unconventional substance — mayonnaise. The condiment mimics the behavior of more complex materials under pressure but in a much more controlled setting.

“We’re still working on the same problem, which is the structural integrity of fusion capsules used in inertial confinement fusion, and Hellmann’s Real Mayonnaise is still helping us in the search for solutions,” said Banerjee, the Paul B. Reinhold Professor of Mechanical Engineering and Mechanics at Lehigh University.

“We use mayonnaise because it behaves like a solid, but when subjected to a pressure gradient, it starts to flow,” he says. 

The new findings build upon similar research from 2019, which first examined the Rayleigh-Taylor instability problem in this context. Banerjee and his team utilized a rotating wheel facility to simulate the flow conditions experienced by fusion plasma. They discovered that mayonnaise undergoes distinct phases — first behaving elastically, then plastically, before finally flowing unstably. Understanding these transitions is crucial because it offers clues on how to control or delay the onset of instability in fusion capsules.

From theory to practice

Their latest research goes deeper into the conditions that govern these phase transitions. The study identified specific criteria under which elastic recovery is possible, deemed vital for delaying or suppressing instability. These insights could guide the design of future fusion capsules, ensuring they remain stable under extreme conditions.

Yet, there remains a critical question: how applicable are these findings to actual fusion capsules, where the materials involved differ significantly in their properties? Banerjee and his team addressed this by non-dimensionalizing their data, allowing them to predict behaviors in fusion capsules despite the differences in material properties.

As Banerjee explains, this research is part of a global effort to make fusion energy a reality. By refining the understanding of fluid dynamics through such innovative experiments, researchers hope to bring us closer to a future powered by clean, limitless energy.

“We’re another cog in this giant wheel of researchers,” he says. “And we’re all working towards making inertial fusion cheaper and therefore, attainable.”

The findings appeared in the journal Physical Review E.