A team of researchers from Lawrence Livermore National Laboratory, UCSD, and SLAC National Accelerator Laboratory have made advancements in a longstanding issue of laser-induced shock experiments. This breakthrough utilizes X-ray diffraction to measure aluminum ablation depth accurately.
When a laser beam is loaded on a material, several complex processes take place that are invisible to the naked eye. Researchers use computer simulations to better understand these processes.
This simulation relies on the equation of state (EOS) model to describe the thermodynamic properties of a material. EOS models demonstrate how the thermodynamic properties of a material behave under extreme conditions.
However, EOS models have proven ineffective in sufficiently addressing laser ablation. Laser ablation is a process of material removal from a solid surface using a laser beam.
Laser Ablation delivers the shock waves that result in a high-density state required for high-pressure experiments such as inertial confinement fusion (ICF). Regardless, tracking ablation depth during this process has always been difficult, resulting in inaccuracy.
Previous approaches relied on post-irradiation analysis of the material, which makes it difficult or impossible to track the evolution of the material. To overcome these limitations, research led by Sophie Parsons utilized X-ray diffraction data from a laser experiment in 2016.
The team analyzed this data to extract new insights into aluminum’s solid phases. They applied advanced mathematics to compare unshocked aluminum to the amount of ablated aluminum.
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Scientists found a significant amount of aluminum transforming into plasma (the fourth state of matter) within the first ten picoseconds of the laser’s interaction with the aluminum surface. This plasma layer was approximately 500-nanometer thick.
“This is likely due to the rapid formation of an approximately 500-nanometer thick plasma layer at the laser-illuminated surface, which is what we are referring to as the ‘ablation depth,” says the co-author Mike Armstrong.
After this initial phase, researchers revealed a steady material loss as the shock wave propagates through the remaining unablated aluminum.
“This technique gives a direct measurement of the shock wave propagation in the bulk target, enabling an ability to discern early timescale physics from late timescale effects not available in postmortem analysis,” mentions the study.
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Journal Reference
- S. E. Parsons, M. R. Armstrong, H. J. Lee, A. E. Gleason, A. F. Goncharov, J. Belof, V. Prakapenka, E. Granados, F. N. Beg, H. B. Radousky; Study of ablation and shock generation across three orders of magnitude of laser intensity with 100 ps laser pulses. Applied Physics Letters. 14 October 2024; 125 (16): 164104. DOI: 10.1063/5.0222979
