Last month, the US National Ignition Facility (NIF) fired a laser at full power for the first time since December. This time, it achieved the decades-old goal of ‘ignition’ by producing more energy than it consumed during the nuclear reaction. The most recent run didn’t quite match up: NIF only delivered 4% of the output it did late last year.
Building on NIF’s success, they are now enhancing the program’s experimental capabilities in an attempt to better understand the capabilities of fusion facilities. here, Nature We look at the future of NIF and whether it will drive global efforts to bring clean energy to the planet in abundance.
What is the purpose of your latest experiment?
Based at Lawrence Livermore National Laboratory (LLNL) in California, the NIF is a stadium-sized facility that fires 192 lasers into a small gold cylinder containing a diamond capsule. Inside the capsule are frozen pellets of the hydrogen isotopes deuterium and tritium. The laser causes an implosion, generating extreme heat and pressure to fuse the hydrogen isotopes into helium, releasing additional energy.
One of the main challenges in making this scheme work is the production of the diamond capsules. Even the smallest defects (bacterial-sized pockmarks, metallic contamination, changes in shape and thickness) affect implosion and affect the pressure and heat that drive the fusion reaction.
Record-breaking experiments in 2021 and 2022 used the best capsules available, but while waiting for a new batch in March, scientists at NIF discovered capsules that were thicker on one side than the other. Modeling suggested that this imperfection could be offset by adjusting the beam from the laser to produce a more uniform implosion. Richard Town, a physicist who heads the inertial confinement fusion science program at LLNL, says this was a test of their theoretical predictions.
The results fell short of their expectations, and researchers are now working to understand why. will deepen,” says Towne.
What next for NIF?
Scientists last December succeeded in prolonging the fusion reaction by increasing the energy of the laser and increasing the thickness of the capsule. An experiment later this year will follow a similar strategy, says physicist Annie Kritcher, who is leading the design of the campaign.
In the long term, the goal is to increase the amount of energy produced by fusion reactions to hundreds of megajoules from the 3.15 megajoules created last year. Towne sees a viable avenue to increase the energy yield of NIF to tens of megajoules, among other things, by further boosting the laser’s energy entering the target. But he warns that NIF may soon need a major security upgrade. The facility has only been rated for a maximum fusion power output of 45 megajoules. of concrete walls need to be reinforced.
How does this help propel the creation of Earth’s fusion energy?
NIF was never designed as a power plant. Its primary purpose was to help scientists demonstrate the reliability and safety of the weapons in the U.S. nuclear stockpile by replicating and studying nuclear weapon reactions. But what ignited in December was “a gateway event that opens the door to energy programs,” said Stephen Dean, president of Fusion Power Associates, an advocacy group in Gaithersburg, Maryland.
This record-breaking experiment produced about 50% more energy than was fed into a gold cylinder. Importantly, it was about 13 times the energy concentrated in the fuel pellets inside. For Max Karasik, a physicist at the Naval Research Laboratory in Washington, D.C., this highlights a potential avenue he and others are pursuing: dump gold cylinders and direct lasers into fuel pellets. An experimental design known as direct drive that focuses on .
In this configuration, “more energy is available to compress the fuel pellets,” says Karasik.
But the future challenges of fusion energy are daunting. NIF’s laser consumed 322 megajoules of energy in a landmark experiment in December. To power the public, a laser fusion plant would need to produce 100 times his input energy, and its laser would need to fire about 10 times per second, Dean said. This means designing systems that can precisely focus and fire lasers at hundreds of thousands of targets each day.
With its current design, NIF will continue to be a place where scientists can learn from high-yield laser fusion experiments, lab officials say. But in the meantime, private companies are increasingly focusing on alternative solutions.
Last year, the administration of US President Joe Biden laid out a vision of public-private partnerships in fusion energy at a summit at the White House. The private sector takes the lead as a pioneer in new fusion technologies, and the U.S. Department of Energy (DOE), of which NIF is a part, advances knowledge in a wide range of areas such as materials science, advanced manufacturing and modeling. . Product commercialization.
Over the next 18 months, DOE will distribute $50 million in grants to private fusion companies in a milestone-based program modeled on partnerships between NASA and space transportation companies such as SpaceX. However, laser fusion companies will be competing with other companies pursuing fusion designs. One of his most popular is a tokamak. A tokamak is a device that generates a magnetic field to confine the burning plasma generated by a nuclear fusion reaction in a doughnut-shaped “torus”. This is the approach used at his ITER, the world’s largest fusion experiment in Saint-Paul-les-Durance, France.
What are the odds of success?
The old joke about fusion energy is that it’s 50 years away and always will be. Many scientists now say the frontier of that equation is closer to 20 to 30 years, but it’s really just a matter of funding, said former Lawrence Livermore National Laboratory scientist, now says his Pravesh Patel, scientific director for Focused Energy in Austin. , Texas, a private laser fusion company.
“As a scientist, I think fusion energy is inevitable,” he says. “The question is how quickly do you want it to work, and that depends on your resources.”
This article is reproduced with permission and was first published on April 26, 2023.
