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LLNL Experiment Reaches Threshold of Nuclear Fusion Ignition

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An experiment at the Lawrence Livermore National Laboratory (LLNL) National Ignition Facility (NIF) has triggered ignition for the first time. Ignition is the process that amplifies energy output from nuclear fusion and that could provide an avenue for clean energy, as well as provide answers to many long-held questions in physics.

In the Aug. 8 experiment, which LLNL reported today, scientists achieved an energy yield of 1.3 MJ — more than the agreed-upon threshold for the onset of ignition — and successfully re-created the extreme temperatures and pressures found at the heart of the sun. The advancement produced more energy than any previous inertia confinement fusion experiment, proved that ignition is possible, and took researchers to the cusp of realizing fusion ignition.

The experiment focused laser light from the NIF, which is the size of three football fields, onto a target the size of a BB, which produces a hot spot the diameter of a human hair — generating more than 10 quadrillion watts of fusion power for 100 trillionths of a second.

While the results have yet to go through the peer-review process, initial analysis shows an 8× improvement over experiments conducted in spring 2021 and a 25× increase over NIF’s 2018 record yield.

Imperial College London (ICL) physicists are among those helping analyze the data.

The experiment built on progress made over the previous several years by the NIF team, including new diagnostics; target fabrication improvements in the hohlraum, capsule shell, and fill tube; improved laser precision; and design changes to increase the energy coupled to the implosion and the compression of the implosion.

Where the type of nuclear reaction that fuels current power stations — fission — is the splitting of atoms to release energy, fusion instead forces hydrogen atoms together to gain energy, producing a large amount energy and limited radioactive waste.

For this reason, a way to create efficient fusion reactions has been sought for decades to produce clean energy using few resources.

The NIF experiment was the first to reach the stage of ignition, which allowed considerably more energy to be produced than ever before. This paves the way for “break even,” which is the state at which input energy is matched by the energy put out, IPL said, in an independent release.

“Gaining experimental access to thermonuclear burn in the laboratory is the culmination of decades of scientific and technological work stretching across nearly 50 years,” said Thomas Mason, director of Los Alamos National Laboratory. “This enables experiments that will check theory and simulation in the high energy density regime more rigorously than ever possible before and will enable fundamental achievements in applied science and engineering.”

Steven Rose, co-director of the Center for Inertial Fusion Studies at Imperial College London, called the demonstration, “the most significant advance in inertial fusion since its beginning in 1972.”

“What has been achieved has completely altered the fusion landscape and we can now look forward to using ignited plasmas for both scientific discovery and energy production,” Rose said.

Researchers worldwide, ICL said, are currently trying to produce fusion energy in two main ways. The NIF focuses on inertial confinement fusion, which uses a system of lasers to heat fuel pellets to produce a plasma. The pellets themselves contain so-called heavy versions of hydrogen — deuterium and tritium — that are easier to fuse and that produce more energy.

The pellets must be heated and pressurized to conditions found at the center of the sun, which is a natural fusion reactor.

At such a condition, fusion reactions release several particles. “Alpha” particles interact with the surrounding plasma and heat it up further. The heated plasma then releases more alpha particles.

That self-sustaining reaction is called ignition.

“This phenomenal breakthrough brings us tantalizingly close to a demonstration of ‘net energy gain’ from fusion reactions—just when the planet needs it,” said Arthur Terrell, in the Department of Physics at ICL.

NIF lasers have already created the most extreme conditions on Earth, and the new work appears to double that previously achieved temperature, according to Brian Appelbe, in the Centre for Inertial Fusion Studies at ICL. The progress, said Aidan Crilly, from the same center, could also enable the study of states of matter that scientists have not yet been able to create in the lab, including those found in stars and supernovae.

“We could also gain insights into quantum states of matter and even conditions closer and closer to the beginning of the Big Bang — the hotter we get, the closer we get to the very first state of the universe,” Crilly said.

“This result is a historic step forward for inertial confinement fusion research, opening a fundamentally new regime for exploration and the advancement of our critical national security missions,” LLNL Director Kim Budil said. “It is also a testament to the innovation, ingenuity, commitment, and grit of this team and the many researchers in this field over the decades who have steadfastly pursued this goal.”

Los Alamos National Laboratory, Sandia National Laboratories, and the University of Rochester’s Laboratory for Laser Energetics are collaborators on the LLNL work.

The research has not yet been published.

This article has been updated.

Photonics Spectra
Oct 2021
GLOSSARY
laser fusion
Optical confinement of matter with high field energies intended to induce a stable nuclear fusion interaction.
plasma
A gas made up of electrons and ions.
quantum
Smallest amount into which the energy of a wave can be divided. The quantum is proportional to the frequency of the wave. See photon.
laserslaser fusionignitionfusion ignitionAmericassolarResearch & TechnologyeducationplasmonicsplasmanuclearextremeQuantum Energy and Sustainable Solar TechnologiesquantumLLNLNIFICLenergyTech Pulse

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