To achieve fusion, the U.S. National Ignition Facility focuses its lasers onto a gold cylinder containing a diamond capsule filled with hydrogen isotopes. NIF could need safety upgrades, if its energy yields continue to climb. Credit: UPI/Alamy Stock Photo
Last month, the US National Ignition Facility (NIF) fired its lasers up to full power for the first time since December, when it achieved its decades-long goal of ‘ignition’ by producing more energy during a nuclear reaction than it consumed. The latest run didn’t come close to matching up: NIF achieved only 4% of the output it did late last year. But scientists didn’t expect it to.
Building on NIF’s success, they are now flexing the programme’s experimental muscles, trying to better understand the nuclear-fusion facility’s capabilities. Here, Nature looks at what’s to come for NIF, and whether it will propel global efforts to create a vast supply of clean energy for the planet.
WHAT WAS THE GOAL OF THE LATEST EXPERIMENT?
NIF, based at Lawrence Livermore National Laboratory (LLNL) in California, is a stadium-sized facility that fires 192 lasers at a tiny gold cylinder containing a diamond capsule. Inside the capsule sits a frozen pellet of the hydrogen isotopes deuterium and tritium. The lasers trigger an implosion, creating extreme heat and pressure that drive the hydrogen isotopes to fuse into helium, releasing additional energy.
One of the main challenges in getting this scheme to work is fabricating the diamond capsule. Even the smallest defects — bacterium-sized pockmarks, metal contamination or variations in shape and thickness — affect the implosion, and thus the pressure and heat that drive the fusion reactions.
Record-breaking experiments in 2021 and 2022 used the best capsules available, but in March, while waiting for a new batch, NIF scientists ran an experiment with a capsule that was thicker on one side than the other. Modelling suggested that they could offset this imperfection by adjusting the beams coming from the lasers, to produce a more uniform implosion. This was a test of their theoretical predictions, says Richard Town, a physicist who heads the lab’s inertial-confinement fusion science programme at the LLNL.
The results fell short of their predictions, and researchers are now working to understand why. But if this line of investigation pays off, Town says, “it opens up more capsules for us to use and will improve our understanding of implosion”. READ MORE...
NIF, based at Lawrence Livermore National Laboratory (LLNL) in California, is a stadium-sized facility that fires 192 lasers at a tiny gold cylinder containing a diamond capsule. Inside the capsule sits a frozen pellet of the hydrogen isotopes deuterium and tritium. The lasers trigger an implosion, creating extreme heat and pressure that drive the hydrogen isotopes to fuse into helium, releasing additional energy.
One of the main challenges in getting this scheme to work is fabricating the diamond capsule. Even the smallest defects — bacterium-sized pockmarks, metal contamination or variations in shape and thickness — affect the implosion, and thus the pressure and heat that drive the fusion reactions.
Record-breaking experiments in 2021 and 2022 used the best capsules available, but in March, while waiting for a new batch, NIF scientists ran an experiment with a capsule that was thicker on one side than the other. Modelling suggested that they could offset this imperfection by adjusting the beams coming from the lasers, to produce a more uniform implosion. This was a test of their theoretical predictions, says Richard Town, a physicist who heads the lab’s inertial-confinement fusion science programme at the LLNL.
The results fell short of their predictions, and researchers are now working to understand why. But if this line of investigation pays off, Town says, “it opens up more capsules for us to use and will improve our understanding of implosion”. READ MORE...
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