Lab Report

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The Lab Report is a weekly compendium of media reports on science and technology achievements at Lawrence Livermore National Laboratory. Though the Laboratory reviews items for overall accuracy, the reporting organizations are responsible for the content in the links below.

Aug. 27, 2021

NIF

The National Ignition Facility at the Lawrence Livermore National Laboratory in Livermore, Calif. The blue sphere in the center is the Target Chamber where the fusion reactions occur.

‘Wright Brothers moment’

The Lawrence Livermore National Laboratory announced a key achievement in fusion research on Tuesday [Aug. 17]. Fusion, the lesser known and opposite reaction to nuclear fission, is when two atoms slam together to form a heavier atom and release energy. It is the way the sun makes energy.

“Our result is a significant step forward in understanding what is required for it to work. To me, this is a Wright Brothers moment,” Omar A. Hurricane, Chief Scientist for the Inertial Confinement Fusion Program at the Lawrence Livermore National Laboratory, told CNBC.

“It’s not practical, but we got off the ground for a moment,” Hurricane said.

The Livermore, Calif.-based lab announced it had, back on Aug. 8, been able to produce 1.3 megajoules of energy at its National Ignition Facility, albeit very briefly.

At the National Ignition Facility, which is the size of three football fields, super powerful laser beams recreate the temperatures and pressures similar to what exists in the cores of stars, giant planets and inside exploding nuclear weapons, a spokesperson tells CNBC.

NIF science mag

An artist’s rendering shows how the National Ignition Facility’s 192 beams enter an eraser-size cylinder of gold and heat it from the inside to produce X-rays, which then implode the fuel capsule at its center to create fusion.

Explosive new result

More than a decade ago, the world’s most energetic laser started to unleash its blasts on tiny capsules of hydrogen isotopes, with managers promising it would soon demonstrate a route to limitless fusion energy. Now, the National Ignition Facility (NIF) has taken a major leap toward that goal. Last week, a single laser shot sparked a fusion explosion from a peppercorn-size fuel capsule that produced eight times more energy than the facility had ever achieved: 1.35 megajoules (MJ ) — roughly the kinetic energy of a car traveling at 160 kilometers per hour. That was also 70 percent of the energy of the laser pulse that triggered it, making it tantalizingly close to “ignition”: a fusion shot producing an excess of energy.

“After many years at 3 percent of ignition, this is super exciting,” says Mark Herrmann, head of the fusion program at Lawrence Livermore National Laboratory, which operates NIF.

NIF’s latest shot “proves that a small amount of energy, imploding a small amount of mass, can get fusion. It’s a wonderful result for the field,” says physicist Michael Campbell, director of the Laboratory for Laser Energetics (LLE) at the University of Rochester.

“It’s a remarkable achievement,” adds plasma physicist Steven Rose, co-director of the Centre for Inertial Fusion Studies at Imperial College London. “It’s made me feel very cheerful. … It feels like a breakthrough.”

NIF physics today

Preamplifiers at the National Ignition Facility boost the energy of the laser beams that ultimately irradiate hydrogen fuel. The photo is color-enhanced. Credit: Damien Jemison/LLNL.

Laser fusion milestone

Lawrence Livermore National Laboratory (LLNL) announced today [Aug. 17] that it has produced a fusion reaction in the laboratory that yielded more energy than was absorbed by the fuel to initiate it.

Zapping a BB-size capsule of fusion fuel with UV light from 192 lasers at the lab’s $3.5 billion National Ignition Facility (NIF), scientists say they sparked fusion reactions that released 1.3 megajoules of energy, about five times the 250 kilojoules that were absorbed by the capsule.

That energy emission from the tiny blob of plasma — roughly a cube with sides measuring the width of a human hair — occurred within about 100 trillionths of a second to yield more than 1016 watts of power.

The shot, which occurred on Aug. 8, demolished the facility’s previous record yield of 170 kJ, observed in February, and was 25 times as high as the best results obtained just a year ago. “Everyone has a spring in their step,” says NIF director Mark Herrmann. The results have not yet been peer reviewed.

Although the achievement represents a milestone in fusion research, the laboratory stopped short of declaring ignition, the goal for which NIF was named and which it had planned to achieve by 2012. The fusion yield fell short of the 1.9 MJ that the NIF laser brought to bear on the hollow target, called a hohlraum, in which the fuel capsule was suspended. A 1997 National Academy of Sciences review of NIF’s design defined ignition as fusion yield equal to or more than the laser energy input. In NIF’s approach, known as indirect drive, 85 percent of the laser’s energy is lost in the conversion of UV to X-rays that occurs inside the hohlraum.

NIF BBC

The research takes place at the National Ignition Facility in Livermore, California.

Threshold of key nuclear fusion goal

The National Ignition Facility uses a powerful laser to heat and compress hydrogen fuel, initiating fusion.

An experiment suggests the goal of "ignition," where the energy released by fusion exceeds that delivered by the laser, is now within touching distance.

Harnessing fusion, the process that powers the Sun, could provide a limitless, clean energy source.

In a process called inertial confinement fusion, 192 beams from NIF's laser — the highest-energy example in the world — are directed towards a peppercorn-sized capsule containing deuterium and tritium, which are different forms of the element hydrogen.

This compresses the fuel to 100 times the density of lead and heats it to 100 million degrees Celsius — hotter than the centre of the Sun. These conditions help kickstart thermonuclear fusion.

An experiment carried out on Aug. 8 yielded 1.35 megajoules (MJ) of energy — around 70 percent of the laser energy delivered to the fuel capsule. Reaching ignition means getting a fusion yield that's greater than the 1.9 MJ put in by the laser.

“This is a huge advance for fusion and for the entire fusion community,” Debbie Callahan, a physicist at the Lawrence Livermore National Laboratory, which hosts NIF, told BBC News.

mushroom cloud

The Weather Research and Forecasting model has been a mainstay in weather forecasting and cloud modeling for decades.

Simulating nuclear cloud rise

For decades, understanding the behavior of a nuclear mushroom cloud was done with careful analysis of observations made during the testing era. Old photos, outdated film and incomplete weather data made precise calculations difficult. Now, with results published in Atmospheric EnvironmentLawrence Livermore National Laboratory (LLNL) scientists are improving our understanding of nuclear cloud rise using a widely adopted and strongly validated weather modeling tool.

The Weather Research and Forecasting (WRF) model has been a mainstay in weather forecasting and cloud modeling for decades. The model source code is maintained by the National Center for Atmospheric Research, but it is community-developed, using several contributions from researchers at LLNL. In particular, the LLNL version of WRF is used at the National Atmospheric Release Advisory Center to simulate the movement and turbulence of airborne particulates flowing around terrain features and buildings. Compared to the lower-fidelity simulations often used to model cloud rise for emergency response, a WRF-based model of a nuclear cloud incorporates time-varying weather for the exact location under study. This adaptability and high resolution appealed to one of the paper’s authors, Livermore mechanical engineer Katie Lundquist.

“Because we have so much experience developing the model for meter-scale resolutions, we thought this model was very well-suited to modeling cloud rise,” she said. Additional co-authors on the paper include Robert Arthur, Jeffrey Mirocha, Stephanie Neuscamman, Yuliya Kanarska and John Nasstrom.

spectrometer

Layout of the spectrometer, which will provide high-resolution measurements of a challenging feature of high energy density matter produced by National Ignition Facility experiments. Credit: Image by Neil Ose/LLNL.

Probing extreme matter

Scientists at Lawrence Livermore National Laboratory (LLNL) have collaborated with Princeton Plasma Physics Laboratory (PPPL) to design a novel X-ray crystal spectrometer to provide high-resolution measurements of a challenging feature of high energy density (HED) matter produced by National Ignition Facility (NIF) experiments.

The work is featured in a paper in the Review of Scientific Instruments that describes the new crystal shape being fabricated for NIF, the world’s most energetic laser.

Laser-produced high energy density plasmas, similar to those found in stars, nuclear explosions and the core of giant planets, may be the most extreme state of matter created on Earth.

PPPL previously built a spectrometer for NIF that was quite successful. The spectrometer, delivered in 2017, provides high-resolution measurements of the temperature and density of NIF extreme plasmas for inertial confinement fusion experiments, and the data obtained was presented in invited talks and peer-reviewed publications.

The instruments measure profiles of key parameters such as the ion and electron temperatures in large volumes of hot plasmas that are magnetically confined in doughnut-shaped tokamak fusion devices to facilitate fusion reactions. By contrast, NIF laser-produced HED plasmas are tiny, point-like substances that require differently designed spectrometers for high-resolution studies.