A year ago, researchers at the Lawrence Livermore National Laboratory in California said they had achieved a net energy gain in a fusion reaction—a breakthrough seen as the "holy grail" of clean energy. The lab has now demonstrated that the achievement, known as ignition, was no fluke, Nature reports. It says it was able to repeat the feat at least three times in five experiments this year. Two other attempts probably achieved ignition but the measurements weren't certain enough for it to be confirmed. Fusion, unlike nuclear fission, does not produce radioactive waste and while scaling the process up will likely take many years, the breakthrough has raised hopes of creating an unlimited source of clean energy.
The lab has been firing 192 laser beams at a pellet of hydrogen fuel inside a diamond capsule housed in a gold cylinder, CNN reports. The lab says it "crowned six decades of research and development" last year when the reaction generated more energy that it took to power. In a report on its progress, the lab said it achieved its highest yield in July when the reaction almost doubled the input, with the reaction releasing 3.88 megajoules of energy after the lasers delivered slightly over 2 megajoules. The lab says the reaction creates higher temperatures than those inside the sun, which, like other stars, is powered by fusion.
Brian Appelbe, a research fellow from the Centre for Inertial Fusion Studies at Imperial College London, tells CNN that replicating the reaction demonstrates the "robustness" of the process and scientists are learning more from every attempt. "This provides valuable information to the scientists in addressing the next challenge to be overcome: how to maximize the energy that can be obtained," he says. Nature reports that the Biden administration is building three new research centers to advance the technology. "Harnessing fusion energy is one of the greatest scientific and technological challenges of the 21st Century," says US Secretary of Energy Jennifer Granholm. "We now have the confidence that it's not only possible, but probable, that fusion energy can be a reality." (More nuclear fusion stories.)