Thanks to These Mighty Lasers, We're at the 'Threshold' of Nuclear Fusion Ignition

Thanks to These Mighty Lasers, We’re at the ‘Threshold’ of Nuclear Fusion Ignition

A breakthrough experiment last month at Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) in California has turned up a whopping 1.3 megajoules of energy, or about three percent of the energy contained in one kilogram of crude oil. The work, as outlined in the journal Physical Review E, puts physicists “at the threshold of fusion ignition,” according to the lab’s press release.

Nuclear fusion, in the simplest terms, is a reaction in which atoms are smashed together to generate an abundance of energy. In some ways, it’s less dangerous than nuclear fission—a process that involves splitting heavy, unstable atoms into two lighter ones—and has the potential to create a lot more energy.

All of today’s functional nuclear power plants currently use nuclear fission, and scientists have long been on the hunt for a way to make nuclear fusion a reality; consider it a kind of holy grail of clean energy.

Around the world, various groups are building reactors called tokamaks and stellarators that are carefully designed to withstand enormous temperatures and the stresses involved in containing fusion’s streams of plasma ions. For the most part, these reactors are supercooled and use induced magnetic fields to contain the sun-hot plasma safely. But magnetic fusion with tokamak reactors isn’t the only game in tow​​n.

This brings us back to the National Ignition Facility, which is about the size of three football fields. Instead of the usual tokamak or stellarator reactor, the NIF contains an enormous laser, powerful enough to heat atoms into the plasma state. “It precisely guides, amplifies, reflects, and focuses 192 powerful laser beams into a target about the size of a pencil eraser in a few billionths of a second, delivering more than 2 million joules of ultraviolet energy and 500 trillion watts of peak power,” the NIF website explains.

“It is good to diversify approaches and learn from each other in the quest for clean renewable energy.”

NIF’s primary mission is to help deter the threat of nuclear war around the world by continuing to test cutting-edge technological breakthroughs without a full-tilt weapons build. But part of the way they continue to work toward that goal is through a secondary goal of reaching plasma ignition—the industry term for a nuclear fusion plasma that produces more energy than it requires to power up. So far, no facility has achieved plasma ignition.

You can consider this recent accomplishment both very big and very small. The lasers managed to produce an enormous amount of power—about 70 percent of the amount of power it took to generate the laser beams, which is a step in the right direction. “This process requires extreme temperatures of ~100 million degrees and recently has produced 10 quadrillion watts of power, but for a fraction (90 trillionths) of a second,” LLNL physicist Annie Kritcher tells Popular Mechanics in an email. This breaks an existing record from 2018.

A laser bay at the National Ignition Facility in California.
Lawrence Livermore National Laboratory

Kritcher says that scientists have been working to move the needle as high as 70 percent for decades, making this an exciting milestone for the whole nuclear fusion industry. “For the first time in any fusion research facility, we’ve output 70 percent of the laser energy delivered to the target as fusion energy, and exceeded the energy delivered to the capsule that contains the fuel by more than five times,” she says.

That’s good news, but we should still try all sorts of approaches to nuclear fusion, Kritcher explains. “We should continue to pursue other approaches, such as magnetic fusion, due to the difficulties associated with realizing this technology,” she says. “It is good to diversify approaches and learn from each other in the quest for clean renewable energy.”

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