California group using x-ray diffraction to measure ablation depth in aluminum...

28 Nov 2024

...and Rochester’s LLE and Sydor awarded $1.15M DOE Phase II SBIR grant for fusion research.

When laser energy is deposited in a target, numerous complex processes take place too rapidly to observe visually. To study and adapt such processes, researchers often use computer modeling. However, such simulations rely on accurate equation-of-state (EOS) models to describe the thermodynamic properties of a target material under such extreme conditions.

One process that is insufficiently addressed in current EOS models is laser ablation, whether by vaporization or plasma formation. This mechanism delivers a shock into the material, ultimately resulting in the high densities required for high pressure experiments such as inertial confinement fusion.

To better understand laser–matter interactions with regard to ablation, researchers from Lawrence Livermore National Laboratory (LLNL), the University of California, San Diego, SLAC National Accelerator Laboratory have conducted a study that represents the first example of using X-ray diffraction to make direct time-resolved measurements of an aluminum sample’s ablation depth. The research is described in Applied Physics Letters.

Controlling material ablation depths is crucial for various scientific and industrial processes, including laser fusion and astrophysical research, among other areas. However, measuring ablation depth in the picosecond regime is a longstanding issue of laser-induced shock experiments. This is because previous approaches have generally relied on post-irradiation analysis of the target material, which makes it difficult or impossible to track the evolution of material response.

The study, led by Sophie Parsons, a UCSD graduate student participating in LLNL’s Academic Cooperation Program, utilized X-ray diffraction data that was previously collected by LLNL scientists Mike Armstrong, Harry Radousky and Jon Belof during laser experiments in 2016. The group analyzed this data to extract new information from the solid phases of aluminum.

The team compared the unshocked thickness of aluminum to the amount of ablated aluminum over time to obtain in situ measurements as shock waves propagated through the target metal. Their in-situ method enabled them to directly measure and isolate the effects that occur during the initial laser-surface interaction.

Within the first 10 picoseconds of the laser’s interaction with the aluminum surface, researchers observed a rapid decrease in the volume of solid material. “This is likely due to the rapid formation of an approximately 500-nm thick plasma layer at the laser-illuminated surface, which is what we are referring to as the ablation depth,” said Armstrong, co-author of the paper.

This research is part of an ongoing series of studies under the Materials Science in Extreme Environments University Research Alliance (MSEE). Future work could include the generation of a comprehensive database of ablation depths, said Radousky, LLNL’s MSEE principal investigator.

LLE and Sydor awarded $1.15M DOE Phase II SBIR grant for fusion research

The University of Rochester’s Laboratory for Laser Energetics (LLE) is collaborating with Sydor Technologies, which has been awarded a $1.15 million Phase-II Small Business Innovation Research grant from the US Department of Energy for their project “Plasma-Electrode Pockels Cells for Inertial Fusion Facilities.”

This academic-industry collaboration is aiming to advance the development of optical devices for high-powered laser systems. The project will focus on commercializing mid-scale plasma-electrode Pockels cell (mPEPC) technology – an electro-optic component essential for enabling and reducing the cost of future fusion facilities.

The mPEPC technology offers several benefits for inertial fusion applications:

• Facilitates multipass laser amplification, maximizing performance while reducing costs and facility size.
• Enables high-power, high-energy modular lasers necessary for scalable inertial fusion systems.
• Integrates optical isolation and retroreflection protection within high-energy laser systems without additional optical components.
• Pioneers future commercial facility designs by enabling various modular and economically reproducible configurations.

The Rochester statement says that the mPEPC plays a “vital role in advancing inertial fusion research and development”. mPEPC technology was developed by LLE under the U.S. National Nuclear Security Administration funding for next-generation laser technologies.

Dr. David Garand, Principal Investigator at Sydor Technologies, said, “This grant provides the opportunity to work with the experts at LLE while leveraging facility resources to construct a first-article mPEPC electro-optic cell and to further refine plasma-electrode Pockels cell technology.”

Dr. Christopher Deeney, Director of LLE, said, “Our partnership with Sydor Technologies will accelerate the transition of cutting-edge fusion technologies from the lab to commercial applications.”