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.

Feb. 24, 2023


Subcritical tests are held at the Nevada National Security Site (NNSS). Image courtesy of NNSS.

Defense daily

Subcrits on the horizon

The Lawrence Livermore National Laboratory was set to fire the first test in its Nimble series of subcritical experiments in the late summer, a senior lab official recently said.

“The first one [called Nob Hill] is scheduled for August of this year, the next one [Twin Peaks] will be hopefully a few months later and actually Mission Hills … is a few years out,” Bradley Wallin principal associate director for weapons and complex integration at the Lawrence Livermore National Laboratory, said at the Exchange Monitor’s annual Nuclear Deterrence Summit.

The tests share names with California neighborhoods. “I think they’re intended to be locations in the Bay Area,” Wallin said. The teams working on each project choose the project’s name, he said on the sidelines of the annual conference.

In subcritical tests, nuclear weapon labs essentially blow up small pieces of plutonium inside of a steel sphere in the U1a underground facility at the Nevada National Security Site. These detonations bring the plutonium to the threshold of nuclear criticality, the U.S. says, allowing labs to physically test parts of existing weapons without resorting to nuclear explosive tests. The U.S. has not tested a weapon at full yield since 1992.

Livermore is responsible for maintaining the W80 air-launched cruise missile warhead, the W87 intercontinental ballistic-missile warhead and the B83 megaton-capable gravity bomb. The Department of Energy’s National Nuclear Security Administration (NNSA), which owns the U.S. nuclear weapons labs, is dismantling some of the B83 stockpile.


An artist’s rendering of the DICER technology. Image courtesy of Rensselaer Polytechnic Institute.

Dicing it up for exoplanets

Are there other Earth-like planets? In the quest to find planets that orbit stars other than the sun, "Earth 2.0" is the Holy Grail. Earth 2.0 is a planet similar enough to Earth to enable the existence of life as we know it. It would be the right temperature for liquid water, and it would orbit a star with a steady supply of light.

A Lawrence Livermore scientist and Rensselaer Polytechnic Institute researchers are leading a team in pursuit of an idea that could make it possible to find nearby, habitable, Earth-like planets - or prove that they are unlikely to exist - thanks to a new grant from NASA.

With the funding, the team will determine if the idea for a Diffractive Interfero Coronagraph Exoplanet Resolver (DICER) is feasible. Using conventional telescopes, it would take a 20-meter infrared telescope in space to see a planet like the Earth orbiting a star like the sun. That is three times the diameter of the state-of-the-art James Webb Space Telescope and is considered beyond the reach of current technology. With DICER, light from a faint planet is collected by two 10-meter diffraction gratings, which are easier to pack up in a rocket to shoot into space.

DICER is designed to find all habitable zone planets closer than 10 parsecs, or 192 trillion miles. In the "habitable zone," the temperature is right for liquid water. To determine whether conditions are right for life or whether it has already started to develop, scientists look at the air that surrounds the planet. DICER may even be able to detect if the newly discovered exoplanets have atmospheric ozone, a so-called biomarker, that may indicate the existence of life.


Hydrogen absorption at the surface of magnesium diboride (MgB2) studied with first principles simulations. The background depicts MgB2 crystallites. Image by Liam Krauss/LLNL.

hydrogen central logo

Getting the skinny on hydrogen storage

A collaboration including scientists from Lawrence Livermore National Laboratory and colleagues has created 3-4 nanometer ultrathin nanosheets of a metal hydride that increase hydrogen storage capacity. 

There is a need for sustainable energy storage technologies that can address the intermittent nature of renewable energy resources. Hydrogen-based technologies are promising long-term solutions that reduce greenhouse gas emissions. Hydrogen has the highest energy density of any fuel and is considered a viable solution for ground transportation, aircraft and marine vessels.

Complex metal hydrides are a class of hydrogen storage materials that while having high absolute storage capacity, can require extreme pressures and temperatures to achieve that capacity.

The team tackled this challenge by nano-sizing, which increases the surface area to react with hydrogen and decreases the required depth of hydrogenation. Previous studies have analyzed nanoscale magnesium diboride (MgB2), including work by LLNL, however, the material in that study was not as thin and wound up clustering together.

The material created in this most recent collaboration came from solvent-free mechanical exfoliation in zirconia, yielding material that is only 11-12 atomic layers thick and can hydrogenate to about 50 times the capacity of the bulk material.

power grid

A technician examining power grid infrastructure. Image by Adobe Stock.

Powering up the grid

Cold starting an entire electrical grid after a blackout is a complex and delicate process. A hybrid computer model from Sandia National Laboratories that combines optimization, physical simulations, and cognitive models of grid operators promises to come up with a fast and reliable plan to get the lights back on.

While power outages are always disruptive, they typically impact only smaller portions of the overall grid. A complete loss of power over the entire network is much more serious, and requires operators to effectively jump-start the grid with so-called “black start” generators. This involves a complicated balancing act to avoid mismatches between energy generation and consumption, as different sections of the grid are gradually brought back online. Get it wrong and the grid can collapse again.

In a blackout, key components may be damaged and operators may not have a full picture of what is available to them. And while utilities are likely to have a rough idea what the load on different parts of the grid should be, there are no guarantees. “You wind up having to basically feel around in the dark to make sure, ‘Does reality match up with what all of my data tells me?’ ” said Kevin Stamber, the Sandia lead of the project.

That prompted the team to pair a cutting-edge optimization approach created by researchers at Lawrence Livermore National Laboratory and the University of California, Berkeley, with additional modules designed to simulate how the grid could react to the restoration plan, and how the operators implementing it would behave.

icy moons

A newly discovered form of ice might exist on icy moons such as (left to right) Saturn’s moon’s Mimas, Dione and Rhea, on the far side of Saturn’s nearly edge-on rings. Image courtesy of NASA/JPL/Space Science Institute.

Ice, ice baby

Scientists have created a new type of ice that matches the density and structure of water, perhaps opening a door to studying water’s mysterious properties.

The ice is called medium-density amorphous ice. The team that created it, shook regular ice in a small container with centimeter-wide stainless-steel balls at temperatures of –200 degrees Celsius to produce the variant, which has never been seen before. The ice appeared as a white granular powder that stuck to the metal balls. As it turns out, comets are big chunks of low-density amorphous ice.

The results are “pretty convincing”, said Marius Millot, a physicist at the Lawrence Livermore National Laboratory. “This is a great example of how we still have things to understand with water.”