Lab Report

Sept. 2, 2022

A field supervisor performs a final walk-through of Roving Mirror Diagnostic Enclosure 1 at the end of a facility maintenance and reconfiguration period.

Simulating to the core

Located at Lawrence Livermore National Laboratory, the National Ignition Facility’s mission is to achieve fusion ignition with high energy gain. It also aims to explore the behavior of matter under the conditions found within nuclear explosions.

Perhaps what makes it most notable, however, is that it's the largest and most powerful inertial confinement fusion device built to date, and it hosts the world's most energetic laser. This powerful laser also can simulate a planet’s core.

Most of the matter on earth exists at extreme temperatures and pressures. LLNL’s Rick Kraus describes how a laser such as NIF can be used to create those conditions.

New plasma optics could make it possible to boost the peak power of systems like the L3 HAPLS at ELI Beamlines Research Center in the Czech Republic. Photo courtesy of ELI Beamlines.

You got the power

Lawrence Livermore researchers have designed a compact multi-petawatt laser that uses plasma transmission gratings to overcome the power limitations of conventional solid-state optical gratings. The design could enable construction of an ultrafast laser up to 1,000 times more powerful than existing lasers of the same size.

Petawatt (quadrillion-watt) lasers rely on diffraction gratings for chirped-pulse amplification (CPA), a technique for stretching, amplifying and then compressing a high-energy laser pulse to avoid damaging optical components. CPA, which won a Nobel Prize in physics in 2018, is at the heart of the National Ignition Facility's Advanced Radiographic Capability as well as NIF's predecessor, the Nova Laser, the world's first petawatt laser.

With a damage threshold several orders of magnitude higher than conventional reflection gratings, plasma gratings "allow us to deliver a lot more power for the same size grating," said former LLNL postdoc Matthew Edwards who is leading the project with LLNL Laser-Plasma Interactions Group Leader Pierre Michel.

Map of the Western United States study area showing topography/bathymetry with WUS256 domain (outer thick black line), labeled major physiographic regions (black lines), plate boundaries (red lines), hotspots (yellow diamonds) and Pleistocene and Holocene volcanic centers (yellow squares and circles, respectively).

Shake it up

Lawrence Livermore scientists have created a new adjoint waveform tomography model that more accurately simulates earthquake and explosion ground motions.

Seismic tomography is a method to estimate the inaccessible three-dimensional (3D) seismic material properties of the Earth, specifically the speeds of compressional and shear waves related composition and temperature variations. It provides images of 3D structures that relate to plate tectonic processes as well as models to better represent seismic wave propagation through Earth’s complex structure.

Unlike typical seismic tomography models, this model uses fully three-dimensional wave propagation simulations to compute the sensitivity of observed seismograms to Earth structure, enabling more accurate simulations and better estimates of seismic source properties.

Evidence from the analysis of lunar samples suggest that although the Earth and moon formed from a giant impact, they mostly retained their primordial abundances of volatile elements, including water. Image by Adam Connell/LLNL.

Earth holds water

Earth’s supply of water is incredibly important for its ability to sustain life, but where did that water come from? Was it present when Earth formed or was it delivered later by meteorites or comets from outer space?

The source of Earth’s water has been a longstanding debate and Lawrence Livermore National Laboratory (LLNL) scientists think they have the answer — and they found it by looking at rocks from the moon.

Since the Earth-moon system formed together from the impact of two large bodies very early in solar system history, their histories are very much linked. And since the moon lacks plate tectonics and weathering, processes that tend to erase or obscure evidence on Earth, the moon is actually a great place to look for clues to the history of Earth’s water.

“Earth was either born with the water we have, or we were hit by something that was basically pure H₂O, with not much else in it. This work eliminates meteorites or asteroids as possible sources of water on Earth and points strongly toward the ‘born with it’ option,” said LLNL cosmochemist Greg Brennecka.

LLNL researchers at Lawrence Livermore and collaborators used a common laser-based metal 3D printing method to produce a new class of high entropy alloys that demonstrated both high yield strength and high ductility beyond other state-of-the-art 3D printed metal alloys. Image courtesy of UMass Amherst.

Alloy me to introduce myself

The aerospace, medical, energy and transportation sectors could get a boost in performance thanks to a new 3D printed alloy that is stronger and more ductile than other additively manufactured materials.

Over the past 15 years, high entropy alloys (HEAs) have become increasingly popular as a new paradigm in materials science. Comprised of five or more elements in near-equal proportions, they offer the ability to create a near-infinite number of unique combinations for alloy design. Traditional alloys, such as brass, carbon steel, stainless steel and bronze, contain a primary element combined with one or more trace elements.

Lawrence Livermore researchers and collaborators combined an HEA with a state-of-the-art 3D printing technique called laser powder bed fusion to develop new materials with unprecedented properties.

The research concludes that 3D printing offers a powerful tool to make geometrically complex and customized parts. In the future, harnessing 3D printing technology and the vast alloy design space of HEAs opens ample opportunities for the direct production of end-use components for biomedical and aerospace applications.