Maximizing pressure in laser-driven shock experiments

Researchers at Lawrence Livermore National Laboratory (LLNL) and the University of California, San Diego have tested two alternative tamper materials, yttrium aluminum garnet (YAG) and gadolinium gallium garnet (GGG), for their potential use in laser-driven shock experiments.

Tamper materials, also called confining media, are placed on the surface of a target during laser shock experiments to confine plasma and play a critical role in maximizing pressure at the shock front. This increased pressure is vital for studying material behavior under extreme conditions, testing the durability of devices like solar cells, and improving simulation models used in scientific and industrial applications.

Traditionally, tamper materials have included amorphous glasses, polymers, stiff plastics, and crystalline materials. However, these materials have limitations, especially at higher laser intensities, where their performance begins to saturate (degrade), resulting in their inability to effectively transmit laser energy and maintain structural integrity.

The researchers aimed to explore whether YAG and GGG, two crystalline materials with promising physical properties, could outperform traditional tampers and expand the range of laser shock experiments.

Using LLNL’s new state-of-the-art Laser Induced compression for Grain scale with High Throughput (LIGHT) system, the team tested the performance of YAG and GGG against traditional tamper materials like sapphire, lithium fluoride (LiF), fused silica, quartz, and BK-7 glass. The LIGHT system allowed them to precisely control laser fluence (energy per unit area) and measure the pressure enhancement and saturation limits of the materials.

At lower laser fluences (5 joules/cm²), the researchers found that tamper selection had little impact on pressure generation. However, YAG and GGG showed promise for higher fluence experiments, where tamper performance becomes more critical.

During the experiment, the team measured the saturation limits of YAG and GGG, which indicate the maximum laser fluence these materials can handle before their optical properties degrade. Both materials exhibited lower-than-expected saturation limits due to surface imperfections like scratches and inclusions.

If surface quality of YAG and GGG can be improved, these materials could outperform traditional tampers like sapphire, which is currently considered the gold standard. In fact, the team has plans to conduct future work to study surface preparation techniques for improved tamper saturation limits of these materials.

Overall, this study paves the way for the development of new tamper materials that could expand the capabilities of laser-driven shock experiments and highlights the importance of surface quality in determining the performance of tamper materials.

[S. Parsons, J. Dominesey, A. Ackerman, M. Armstrong, M. Daeumer, J. Garay, P. Grivickas, F. Jin, K. Rodriguez, H. Radousky, F. Beg, Shock measurements of alternative tamper materials YAG and GGG, Optics Letters (2025), doi: 10.1364/OL.552003.]

–Physical and Life Sciences Communications Tea