As a laser fusion experiment it unleashed an energetic explosion of optimism

[ad_1]

Scientists have tantalizingly come close to reproducing the power of the sun, even if only in a grain of hydrogen for a fraction of a second.

Researchers at the Lawrence Livermore National Laboratory reported Tuesday that by using 192 giant lasers to annihilate a hydrogen pellet, they were able to ignite an explosion of more than 10 quadrillion watts of fusion energy released when hydrogen atoms are fused into helium, the same process that occurs inside the stars.

Indeed, Mark Herrmann, deputy director of the Livermores program for fundamental weapons physics, compared the fusion reaction to the 170 quadrillion watts of sunlight bathing the earth’s surface.

That’s about 10 percent of that, Dr. Herrmann said. And all the fusion energy is emanating from a hot spot about the size of a human hair, he said.

But the explosion, essentially a miniature hydrogen bomb, lasted only 100 trillionths of a second.

However, this has spurred an explosion of optimism for fusion scientists who have long hoped that fusion could one day provide a clean and unlimited source of energy for humanity.

I’m very excited about this, said Siegfried Glenzer, a scientist at the SLAC National Accelerator Laboratory in Menlo Park, Calif., And who had conducted the initial fusion experiments at the Livermore facility years ago, but is not currently involved in the research. . This is very promising for us to get an energy source on the planet that will not emit CO2.

The success also marked a moment of redemption for the laser apparatus the size of a football stadium in Livermores, which goes by the name of the National Ignition Facility, or NIF Despite an investment of billions of dollars, construction began in 1997 and operations started in 2009 the apparatus initially generated almost no fusion at all. In 2014, Livermore scientists finally reported success, but the energy produced back then was miniscule – the equivalent of what a 60-watt light bulb consumes in five minutes.

On August 8, the energy blast was much greater than 70% of the energy of the laser light hitting the hydrogen target. This is still a losing proposition as an energy source, consuming more energy than it produces. But the scientists are confident that further leaps in energy production would have been possible with the experiment set up.

Dr. Herrmann said Livermore scientists would not normally speak until a scientific article describing the findings was published. But these findings spread like wildfire, he said, and so we thought it might be best to disclose some facts now.

Stephen Bodner, a retired plasma physicist who has long been a critic of the NIF, congratulated. I’m surprised, he said. They came close enough to their ignition and draw goal to call it a success.

More promising, fusion reactions for the first time appeared to be self-sustaining, meaning that the torrent of particles flowing outward from the hot spot to the center, the pellet would heat up around the hydrogen atoms and cause them to fuse as well. .

Riccardo Betti, chief scientist at the University of Rochesters Laboratory for Laser Energetics, provided an analogy to the operation of an automotive engine. You supply energy in a very small fraction of the fuel through a spark in the spark plug, and then that energy is amplified by the combustion of the fuel, he said. So, the same thing happened in the Livermore experiment.

Dr. Herrmann was more cautious, noting that the results fell short of the definition established by a National Academy of Sciences report in 1997 that the fusion energy produced must exceed the amount of energy supplied by the hydrogen lasers. . They were in the doorway, he said.

Livermore scientists said they needed to analyze their results more carefully before making more detailed claims.

Dr. Glenzer, however, said he was confident that the merger had spread. The fusion reactions produced a torrent of subatomic particles known as neutrons more than instruments could count.

The data is pretty obvious, Dr. Glenzer said.

The improved fusion results also help the National Ignition Facility meet its primary use for verifying nuclear weapons are working. After the United States suspended underground nuclear testing in 1992, lab officials argued that a way was needed to verify the computer models that replaced the tests.

Dr Herrmann said that within 24 hours of the last experiment, someone working on the nuclear weapons modernization program contacted the NIF team. They are interested in applying this to important questions they have, he said.

The centerpiece of the National Ignition Facility is the target chamber, a 33-foot-wide metal sphere with gleaming diagnostic equipment that radiates outward.

The laser complex fills a building with a footprint equal to three football fields. Each explosion begins with a small laser pulse that is split via partially reflective mirrors into 192 beams, then bounces back and forth through laser amplifiers before converging on a gold cylinder that is about the size and shape of a pencil eraser.

The laser beams enter the top and bottom of the cylinder, vaporizing it. This generates an internal onslaught of X-rays that compresses a BB-sized fuel pellet of carefully frozen deuterium and tritium, the heavier forms of hydrogen. In a short moment, the imploding atoms fuse together.

Since the first promising results in 2014, NIF scientists have been tinkering with the experiment’s setup. The hydrogen-containing capsules are now made of diamond instead of plastic not because the diamond is stronger but because it absorbs X-rays more easily. Scientists have modified the design of the gold cylinder and the laser pulse to reduce the minimum instabilities.

Scientists now also have better diagnostic tools.

After years of only modest improvements, the combinations of changes have begun to pay off and calculations have indicated that the August 8 hit could triple what the NIF had produced in the spring. Instead, the gain was a factor of eight, far more than expected.

I think everyone was surprised, Dr. Herrmann said. Part of the current analysis is figuring out which changes have worked so well.

The NIF itself cannot serve as a blueprint for a future power plant. Its lasers are inefficient and it can only fire once a day. A laser fusion power plant should vaporize the hydrogen pellets at a rate of several per second.

Dr. Glenzer said SLAC was working on a laser system that would work at lower power levels but fire much faster. He said he hoped the merger, overshadowed in recent years by solar energy and other energy technologies, would again gain prominence in efforts to replace fossil fuels.

Federal funding for fusion research is low, even though the Biden administration has placed an emphasis on reducing climate change.

Sometimes it happens that, in the worst year of your funding, you get the best results, said Dr. Glenzer.

Although Dr. Bodner prefers an alternative approach to that of the current experiment, he said the NIF result indicated a path to follow.

Prove to the skeptic that there is nothing fundamentally wrong with the concept of laser melting, he said. It is time for the United States to move forward with a major laser fusion energy program.

Lasers aren’t the only approach to harnessing fusion for future power plants.

Scientists also used donut-shaped reactors called tokamak that use magnetic fields to hold and compress hydrogen. In the late 1990s, the Joint European Torus experiment in England was able to generate 16 million watts of fusion energy for a brief moment, producing around 70% of the energy it consumed. An international project called ITER is now building a larger tokamak reactor in France, which is expected to start operating in 2025.

[ad_2]