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.

Oct. 1, 2021

volcano

A new study led by LLNL scientists examined how shock waves and electric discharges interact in particle-laden flows. The work has implications for environments such as volcanoes, where radio frequency emissions from lightning may transmit information about conditions inside the eruption.

Shock waves are lightning fast

Volcanic eruptions spew lava, rock and ash into the air. When fragments of these materials mix and collide in the outflow, they can create an electric potential large enough to generate lightning.

New research by Lawrence Livermore scientists and collaborators has discovered that standing shock waves in the supersonic outflow of gases prevent electric discharges like sparks and lightning from propagating. This suggests standing shocks formed by a volcanic eruption may suppress or reduce volcano lightning during the initial phase of an eruption.

In nature, electric discharges in the form of lightning are frequently observed not only in thunderclouds, but also in widely diverse environments that exhibit turbulent particle-laden flows, such as volcanic plumes and dust devils.

During electric discharge, radio frequency (RF) emissions can be recorded, providing a means to track the progressive evolution in space and time of the lightning source. Similar to the detection of thunderclouds and storms, RF detection also is now being used to detect and inform on the hazards associated with ash-laden volcanic plumes and ash clouds. In particular, lightning at active volcanoes in a state of unrest can indicate the onset of hazardous explosive activity and the production of ash plumes. In addition, both observable discharges and RF emissions can reveal the mechanisms that initiate the lightning and offer clues about the makeup of the erupting material.

planet

LLNL scientists have developed a new approach using machine learning to study with unprecedented resolution the phase behaviors of superionic water found in ice giants Uranus and Neptune.

Come on in, the water is superionic

The interiors of Uranus and Neptune each contain about 50,000 times the amount of water in Earth’s oceans, and a form of water known as superionic water is believed to be stable at depths greater than approximately one-third of the radius of these ice giants.

Superionic water is a phase of H2O where hydrogen atoms become liquid-like while oxygen atoms remain solid-like on a crystalline lattice. Although superionic water was proposed over three decades ago, its optical properties and oxygen lattices were only accurately measured recently in experiments by LLNL’s Marius Millot and Federica Coppari, and many properties of this hot “black ice” are still uncharted.

Lawrence Livermore scientists have developed a new approach using machine learning to study the phase behaviors of superionic water with unprecedented resolution.

Buried deep within the core of planets, much of the water in the universe may be superionic. Understanding its thermodynamic and transport properties is crucial for planetary science but difficult to probe experimentally or theoretically.

NIF

The interior of the target chamber inside the National Ignition Facility. Technicians can be seen on the left. The target positioner, which holds the target where 192 lasers will be aimed, is on the right.

san diego union tribune

Road to a clean energy future

With a powerful zap from 192 laser beams that lasted less than 9 billionths of a second, scientists at Lawrence Livermore believe they have achieved a major milestone in their research to advance nuclear fusion.

News of the experiment has circulated quickly around the scientific community and stirred optimism that hydrogen fusion may someday provide an abundant and clean source of energy around the globe.

“People have been working at this for decades trying to achieve this,” said Annie Kritcher, a physicist at the Lawrence Livermore National Laboratory and the lead designer for the experiment. “I think it has extremely energized the whole community.”

bullseye

To address porosity and defects in metal 3D printing, LLNL researchers experimented with exotic optical laser beam shapes known as Bessel beams — reminiscent of bullseye patterns. Image by Veronica Chen/LLNL.

Metal 3D printing hits a bullseye

While laser-based 3D printing techniques have revolutionized the production of metal parts by greatly expanding design complexity, the laser beams traditionally used in metal printing have drawbacks that can lead to defects and poor mechanical performance.

Researchers at Lawrence Livermore National Laboratory are addressing the issue by exploring alternative shapes to the Gaussian beams commonly employed in high-power laser printing processes such as laser powder bed fusion (LBPF).

The researchers experimented with exotic optical beam shapes known as Bessel beams — reminiscent of bullseye patterns — which possess a number of unique properties such as self-healing and non-diffraction. They discovered that the application of these types of beams reduced the likelihood of pore formation and “keyholing,” a porosity-inducing phenomenon in LPBF exacerbated by the use of Gaussian beams.

balloon

Laser drive asymmetry is similar to compressing a balloon.

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Exsqueeze me

Imagine having a balloon between both hands and trying to squeeze it with the same force on all sides so that it uniformly shrinks down. However, if you push on one side harder than the other the balloon won’t compress uniformly and will, in fact, move away from the hand that is pushing harder.

The same thing happens when the drive pushing on an inertial confinement fusion (ICF) capsule is imbalanced — if it pushes harder on the top than on the bottom the capsule will move downward. This motion detracts from the energy heating the capsule and generating fusion. A short leap is to imagine two pistons compressing this gas instead of hands.

That is how Dave Schlossberg, Lawrence Livermore staff scientist, explains the effect of laser drive asymmetry.

The team conducted experiments at the National Ignition Facility to investigate a “low-mode” laser asymmetry that was significantly degrading performance. The results from the work led to a detailed understanding of this degradation from the very small-scale up to the largest scale.