Hot stuff: Lab hits milestone on long road to fusion power

Researchers say they have been able to trigger a fusion reaction that briefly held its own, a significant milestone on the long road to fusion power

With 192 lasers and temperatures more than three times warmer than the center of the sun, scientists – at least for a fraction of a second – hit an important milestone on the long road to near-pollution-free fusion energy.

Researchers at the National Ignition Facility at Lawrence Livermore National Lab in California were able to trigger a fusion reaction that briefly sustained itself – a great achievement because fusion requires such high temperatures and pressures that it easily melts out.

The ultimate goal, still years away, is to generate electricity as the sun generates heat by equalizing hydrogen atoms so close together that they combine to form helium, which releases streams of energy.

A team of more than 100 scientists published the results of four experiments that achieved what is known as a burning plasma in Wednesday’s journal Nature. With these results, coupled with the preliminary results announced last August from follow-up experiments, scientists say they are on the threshold of even greater progress: ignition. This is when the fuel can continue to “burn” by itself and produce more energy than is necessary to trigger the initial reaction.

“We’re very close to the next step,” said study lead author Alex Zylstra, an experimental physicist at Livermore.

Nuclear fusion compresses two types of hydrogen found in water molecules. When they melt together, “a small amount (milligrams) of fuel produces enormous amounts of energy, and it is also very ‘clean’ because it does not produce radioactive waste,” said Carolyn Kuranz, an experimental plasma physicist from the University of Michigan who was not one of them. of the research. “It’s basically unlimited, clean energy that can be used anywhere,” she said.

Researchers around the world have been working on the technology for decades, trying different approaches. Thirty-five countries are collaborating on a project in the south of France called the International Thermonuclear Experimental Reactor, which uses huge magnets to control the overheated plasma. It is expected to start operating in 2026.

Previous experiments in the United States and the United Kingdom succeeded in fusing atoms, but did not achieve self-heating, said Steven Cowley, director of the Princeton Plasma Physics Laboratory, which was not part of this study.

But not betting on merger yet.

“The result is scientifically very exciting for us,” said study co-author Omar Hurricane, lead researcher for Lawrence Livermore’s fusion program. “But we are far from useful energy.”

Maybe decades, he said.

It’s already taken several years inside a lab just off Star Trek – one of the movies used the lab as wallpaper for Enterprise’s engine room – and many failed attempts to reach that point. An adjustment that helped: Researchers made the fuel capsule about 10% larger. Now it’s up to the size of a BB.

That capsule fits in a small gold metal can, which the researchers aim 192 lasers at. They heat it to about 100 million degrees, creating about 50% more pressure inside the capsule than what is inside the center of the sun. These experiments created burning plasmas that lasted only a trillionth of a second, but that was enough to be considered a success, Zylstra said.

In total, the four experiments in the Nature study – conducted in November 2020 and February 2021 – produced as much as 0.17 megajoules of energy, which is far more than previous experiments, but still less than a tenth of the power used for to start the process, Zylstra said.

Preliminary results from experiments conducted later in 2021, which are still being reviewed by other scientists, pushed energy production to 1.3 megajoules and lasted 100 trillions of seconds, according to a government press release. But even that is shy of the 1.9 megajoules it takes to break-even.

“The biggest problem with fusion is that it’s difficult,” Princeton’s Cowley said. “Otherwise, it can be the perfect way to make energy – sustainable, abundant, safe and minimal environmental impact.”


Follow Seth Borenstein on Twitter at @borenbears.


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