Take a smidgen of hydrogen, then blast it with lasers to set off a small thermonuclear explosion. Do it right, and maybe you can solve the world’s energy needs.
A small group of startups have embarked on this quest, pursuing their own variations on this theme — different lasers, different techniques to set off the fusion reactions, different elements to fuse together.
Last December, after years of trying, the National Ignition Facility, or NIF, at Lawrence Livermore National Laboratory reported that it had finally lived up to its middle name: ignition. For the first time anywhere, a laser-induced burst of fusion produced more energy than that supplied by the incoming lasers.
“We’re really excited by the NIF results,” said Kramer Akli, who manages the internal fusion energy sciences program at the U.S. Energy Department.
A decade ago, a report by the National Academy of Sciences found much to like in the energy potential of laser fusion but recommended that the United States hold off major investments until ignition was achieved.
That time is now.
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The dream of fusion is easy to explain.
The sun generates heat and light by jamming — fusing — hydrogen atoms together into helium. Harnessing that phenomenon on Earth could lead to a bountiful energy source that does not generate planet-warming carbon dioxide or long-lived radioactive waste.
For more than 70 years, fusion research has largely focused on mimicking the inside of the sun in reactors known as tokamaks, which trap superhot hydrogen gas within strong magnetic fields so that atoms will collide and fuse.
NIF offered another possibility. It was designed primarily to help verify computer simulations of nuclear explosions after a treaty banned tests of actual exploding nuclear weapons. But a secondary aim of NIF was to explore the possibility that technology could be adapted to provide a bountiful, clean source of energy.
Until two years ago, NIF sputtered well short of its goals. But in December 2022, a burst finally crossed the threshold of ignition.
“Simply put, this is one of the most impressive scientific feats of the 21st century,” Energy Secretary Jennifer Granholm said during a celebratory news conference announcing the success.
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Private enterprise is jumping in, too, and scientists are following.
Since the beginning of the year, the Energy Department has gathered views across academia and industry about the technological challenges that stand between the basic science result of NIF and commercial laser fusion power plants hooked onto the electrical grid.
The agency has bestowed modest awards to a couple of the startups to begin designing what such a power plant would look like, and it is looking to finance consortiums of institutions to tackle pieces of laser fusion research, including high-power lasers that are able to fire at high rates, and fuel targets that can be manufactured in quantity at low cost.
Longview Fusion Energy Systems of Orinda, California, has the simplest strategy: Directly replicate NIF’s approach, but use more modern components.
In NIF’s approach, known as indirect drive, the laser beams do not directly hit the hydrogen fuel. Instead, they annihilate a surrounding gold cylinder that is about the size and shape of a pencil eraser. That generates a bath of inward-rushing X-rays that compresses a round pellet that contains a layer of deuterium and tritium, the heavier forms of hydrogen.
The problem is that the extra step of generating X-rays throws away much of the laser energy.
In its place, some, including some at the Naval Research Laboratory, want to attempt direct drive, where lasers directly implode hydrogen pellets, a more energy-efficient approach that would generate more power and potentially more economically viable.
Stephen Obenschain, who led the Naval Research Laboratory laser fusion program for more than two decades, left last year to start a direct-drive fusion company, LaserFusionX. The naval research laboratory researchers have been pushing to use a type of laser that uses argon and fluoride gases to produce ultraviolet laser light.
Computer simulations, they say, indicate that argon-fluoride lasers of modest power could generate energy gains — the ratio of fusion energy output divided by the energy of the incoming lasers — of 100 or more. (The NIF burst in July produced a gain of 1.8.)
Energy gains that high could enable power plants that are smaller and less expensive.
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