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.

Jan. 8, 2021

climate change

Global warming lags behind greenhouse gas emissions, meaning that past emissions continue to heat us into the future. New research finds that the warming ultimately achieved if greenhouse gas concentrations remained at current levels is larger than previously thought.

Paying for past emissions

The planet is committed to global warming more than 3.6 degrees Fahrenheit just from greenhouse gases that have already been added to the atmosphere. This is the conclusion of new research by scientists from Nanjing University, Lawrence Livermore National Laboratory and Texas A&M University.

The team used observations and climate model simulations to re-evaluate how much warming is “in the pipeline” from past emissions. Their estimate is higher than previous estimates because it accounts for changes in the geographic pattern of surface warming.

“Typically, committed warming is estimated assuming that changes in the future will pretty much follow changes in the past,” said LLNL atmospheric scientist Mark Zelinka. “But we now know that this is a bad assumption.”

diamond

A photoconductive switch made from a synthetic, chemical vapor deposition diamond under test.

Diamonds aren’t just for jewelry anymore

As electronic engineers are reaching the physical limits of silicon for semiconductors, researchers at Lawrence Livermore are looking at an alternative material — diamond — as an ultra-wide bandgap semiconductor.

Diamond is known to have better carrier mobility and thermal conductivity, the most important properties for powering electronic devices.

The team explored properties of synthetically made diamonds that are higher quality than naturally occurring ones. They are made using chemical vapor deposition. “In electronics, you want to start with a pure material so you can so you can mold it into a device with the properties you want,” said LLNL physicist Paulius Grivickas.

crystal

Autopack rotates crystal structures in 3D space to minimize their molecules’ projected area. After convergence, it is possible to extract the crystal’s associated packing motif based on relative interplanar angles. In this example, the stacks found after the optimization procedure indicate the structure’s beta packing motif.

Pack it in

Whether organic chemists are working on developing new molecular energetics or creating new blockbuster drugs in the pharmaceutical industry, each is searching how to optimize the chemical structure of a molecule to attain desired target properties.

Part of that optimization includes a molecular crystal’s packing motif, a perceived pattern in how molecules orient relative to one another within a crystal structure. The current packing motif datasets have remained small because of intensive manual labeling processes and insufficient labeling schemes.

To help solve this problem, a team of Lawrence Livermore materials and computer scientists have developed a freely available package, Autopack, which formalizes the packing motif labeling process and can automatically process and label the packing motifs of thousands of molecular crystal structures.

chamber

A color-enhanced image of the inside of a NIF preamplifier support structure.

On the road to a burning plasma

Researchers at the National Ignition Facility (NIF) at Lawrence Livermore say that after a decade of challenges, it’s finally honing in on the right range to reach productive nuclear fusion.

This puts the facility in a slow-motion dead heat with half a dozen major fusion projects around the world that are all, they say, finally striding toward the goal of fusion ignition.

With new target designs and laser pulse shapes, along with better tools to monitor the miniature explosions, NIF researchers believe they are close to an important intermediate milestone known as “burning plasma”: a fusion burn sustained by the heat of the reaction itself rather than the input of laser energy.

clouds

LLNL scientists found that climate models may have overestimated the decade-to-decade natural variability of temperature.

It’s only natural

By looking at satellite measurements of temperature changes in the lower layer of Earth’s atmosphere, scientists found that climate models may have overestimated the decade-to-decade natural variability of temperature.

LLNL statistician Giuliana Pallotta and climate scientist Benjamin Santer created a statistical framework to comprehensively assess the significance of differences between simulated and observed natural variability in mid- to upper tropospheric temperature. The troposphere is the lowest region of the atmosphere, extending from the Earth's surface to a height of about 4 to 12 miles, depending on latitude and season.

The team found that in current and earlier generations of climate models, the natural decade-to-decade variability of tropospheric temperature is systematically too large relative to estimates of natural variability obtained from satellites. Such an overestimate of natural “climate noise” would make it more difficult to identify a human-caused tropospheric warming signal.