Metal Ejecta: Transport, Interaction, and Recollection

Project Overview

This LDRD aimed to develop high-power laser platforms and diagnostic capabilities to study the interactions of metal ejecta. Microjets of ejecta form when shocks break out from free surfaces of materials that have micron-scale surface perturbations, such as grooves or divots. The perturbations invert and can generate micron-scale jets of particles traveling at velocities of several kilometers per second. The literature contains many examples of work that have sought to understand how experimental parameters of drive pressure profile, material type, and surface perturbation geometries affect ejecta characteristics, such as jet velocities, jet densities, and the total amount of mass. But thus far, interactions of jets have largely been ignored by researchers.

In support of understanding ejecta interactions, we developed platforms for the OMEGA Extended Performance and the OMEGA-60 laser facilities to radiograph tin ejecta microjets and their interactions. We took the first time-sequenced images of ejecta interactions and observed that microjets generated at the lower pressure drive pass through each other unattenuated, whereas microjets generated from higher pressures interact strongly, forming a corona of material around the central point of interaction. These previously unobserved interactions provide an important benchmark point for fields that seek to understand the effects of collisions of streams of high-velocity particles. The results from these experiments were compared to radiation hydrodynamics simulations of both the jetting process and the ejecta collisions. While simulations of the jetting process were able to capture much of the physics observed in single jets, simulations of the collisions fell short of reproducing some experimental observations, opening many avenues for new related research.

Mission Impact

This LDRD supported many areas of Lawrence Livermore National Laboratory and NNSA mission spaces, ranging from fundamental science to programmatic applications. The progress made in the LDRD prompted Laboratory programs to fund continued work in this project. More broadly, the work opened many new avenues for experimental investigation through its novel scientific observations. The questions of what physics drives the interaction behavior we observe and why the simulations fail to capture behavior experimentally prompt more diagnostic development, more experiments to be performed, and improved modeling hydrocode modeling capabilities, all of which will contribute to fields that seek to understand the interactions of high-velocity streams of particles, such as are found in metal ejecta microjets. This work supported the NNSA through its development of science and technology tools and capabilities to meet future national security challenges.

Publications, Presentations, and Patents

Haxhimali, T., et al. 2019. "Hydrodynamic Studies in Support of High-Power Laser Experiments to Study Metal Ejecta Interactions." Presented at the 21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter, June. LLNL-PRES-778020
———. 2020a. "Particle Based Studies in Support of High-Power Laser Experiments to Study Metal Ejecta Interactions." Presented at the APS March Meeting 2020, March. LLNL-ABS-795429
———. 2020b. "Hydrodynamic and Atomistic Studies in Support of High Power Laser Experiments for Metal Ejecta Recollection and Interactions." AIP Conference Proceedings 2272 (1): 120006. https://doi.org/10.1063/12.0000824. LLNL-PROC-790058

Mackay, K. K. et al. 2020. "Hydrodynamic Computations of High-Power Laser Drives Generating Metal Ejecta Jets from Surface Grooves." Journal of Applied Physics 128 (21): 215904. https://doi.org/10.1063/5.0028147.

Najjar, F. et al. 2019. "High-Order Lagrangian Hydrodynamics Computations of Surface Perturbations in Shock-Driven Metal." Presented at the 21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter, June. LLNL-PRES-774580.
———. 2020a. "High-Order Lagrangian Hydrodynamics Computations of Surface Perturbations in Shock-Driven Metals." AIP Conference Proceedings 2272 (1): 120018. https://doi.org/10.1063/12.0000915. LLNL-PROC-782037.
———. 2020b. "Experimental and Computational Studies Of Laser-Driven Shocks Through Metal Surface Perturbations and Planar Grooves." Presented at the TMS 2020: 149th Annual Meeting & Exhibition. LLNL-ABS-780377.

Park, H. S., et al. 2019a. "Study of Metal Ejecta Recapture, Interactions and Transport." Presented at the IFSA 2019, September. LLNL-PRES-790582
———. 2019b. "Experiments on Materials in Extreme Conditions at High Power Laser Facilities Part II." Massachusetts Institute of Technology, May.

Saunders, A. M., et al. 2019a. "Development of High Power Laser Platforms to Study Metal Ejecta Interactions." Presented at the 21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter, June. LLNL-PRES-777852
———. 2019b. "Experiments on Materials in Extreme Conditions at High Power Laser Facilities." Massachusetts Institute of Technology, May. LLNL-PRES-776263.
———. 2020a. "Characterizing Laser-Driven Metal Ejecta Interactions." Presented at the 62nd Annual Meeting of the APS Division of Plasma Physics, November. LLNL-PRES-777852.
———. 2020b. "Development of High Power Laser Platforms to Study Metal Ejecta Interactions." AIP Conference Proceedings 2272 (1): 120025. https://doi.org/10.1063/12.0000816. LLNL-PROC-783445.
———. 2021a. "Characterizing Laser-Driven Metal Ejecta Interactions." Presented at the 150th 2021 TMS Annual Meeting and Exhibition, March. LLNL-PRES-820162.
———. 2021b. "Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions." Presented at the LLNL High-Energy-Density Science Center Seminar Series 2021, June. LLNL-PRES-823804.
———. 2021c. "Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions." Presented at the Conference on Science at Extreme Conditions 2021, July. LLNL-PRES- 824798.
———. 2021d. "Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions." Accepted by Physical Review Letters, August. LLNL-JRNL-821330.
———. 2021e. "Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions." To be presented at 2022 TMS Annual Meeting and Exhibition, March. LLNL-ABS-824184.

Stan, C. V. et al. 2021. "Radiographic Areal Density Measurements on the OMEGA EP Laser System." Review of Scientific Instruments 92 (5): 053901. https://doi.org/10.1063/5.0043512 LLNL-CONF-820865.