Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session M02: Ejecta Microphysics IFocus Recordings Available
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Chair: Olivier Durand, CEA de Bruyeres-le-Chatel Room: Anaheim Marriott Platinum 6 |
Tuesday, July 12, 2022 4:00PM - 4:30PM |
M02.00001: Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions Invited Speaker: Alison Saunders The study of high-velocity particle-laden flow interactions is broadly applicable to fields ranging from planetary formation [1] to cloud interactions [2]. Ejecta microjets offer a novel experimental methodology to study such interactions, as microjets consist of micron-scale particles that travel at velocities greater than several kilometers per second. Microjets are generated when a strong shock releases from a surface with a feature, such as a groove or a divot; the feature then inverts as a limiting case of the Richtmyer-Meshkov Instability and forms a propagating jet of material. Recent experiments performed at the OMEGA EP laser facility observed the interaction of two counter-propagating ejecta microjets for the first time. In this presentation, we show these time-sequences of x-ray radiography images of two interacting tin jets [3]. We observe that jets emerging from a shock pressure of 11.7 GPa pass through each other unattenuated, whereas jets emerging from a shock pressure of 116.0 GPa have five times greater densities and interact strongly, forming a cloud around the center-point of interaction. Radiation hydrodynamics simulations of particle-stream collisions capture many of the observed interaction behavior characteristics, but are unable to capture the full spread of the cloud formed. |
Tuesday, July 12, 2022 4:30PM - 4:45PM |
M02.00002: High-Velocity Interactions of Laser-Driven Tin Ejecta Microjets Yuchen Sun, Jeremy Horwitz, Kyle Mackay, Suzanne J Ali, Jon H Eggert, Brandon E Morgan, Fady M Najjar, Hye-Sook Park, Yuan Ping, Jesse E Pino, Camelia V Stan, Alison Saunders Ejecta microjets are generated when a shock breaks out from the free surface of a sample and interacts with a surface feature, such as a groove or a divot, and travel at several kilometers per second. These high-velocity jets can be highly destructive and therefore undesirable in high energy density experiments. Recent studies of laser-driven tin ejecta microjets have demonstrated that two colliding microjets can pass through each other unattenuated or, at higher shock pressures, strongly interact and result in a particle-laden plume. It has long been known that microjet characteristics, such as mass-velocity distributions, vary as a function of shock pressure, but never have differences in interaction behavior been observed. It is unknown if the differences in collisional behavior are due to density differences, material phase effects or other complex phenomena. To that end, we further investigate the interaction of tin eject microjets in order to better understand jet interactions as a function of drive pressure. This work will provide new understanding of materials physics driving microjet interaction dynamics. |
Tuesday, July 12, 2022 4:45PM - 5:00PM |
M02.00003: Relevance of the Fragmentation Zone Propagation model issued from molecular dynamics simulations to interpret photo Doppler velocimetry measurements in microjetting experiments. Jean-René Burie, Olivier Durand, Laurent Soulard, Sébastien Eveillard, Louis-Pierre Terzulli We recently proposed a model of fragmentation of ejected sheets of liquid metal issued from shock-loaded surfaces (microjetting). This model, called Fragmentation Zone Propagation (FZP), results from the analysis of very large-scale Molecular Dynamics (MD) simulations of the phenomenon. We tested its relevance by performing shock-induced experiments of matter ejection on grooved tin samples. We analyzed in particular the behavior of the ejecta cloud using a photon Doppler velocimetry (PDV) setup. We show that, although the FZP model results from simulations performed at much smaller length scales than those of experiments, it may be very helpful to interpret the experiments. In particular, it predicts that the ejecta are not created at the same time in the cloud: they are created first near the tip of the sheets. Then the fragmentation zone, where the ejecta are created, counter-propagates in the sheet towards the free surface. This is what we observe in our PDV measurements. |
Tuesday, July 12, 2022 5:00PM - 5:15PM |
M02.00004: Computational Studies to Understand Scaling in Laser-Driven Tin Ejecta Microjets Kyle Mackay, Fady M Najjar, Alison Saunders, Jesse E Pino, Suzanne J Ali, Jon H Eggert, Jeremy Horwitz, Brandon E Morgan, Hye-Sook Park, Yuan Ping, Camelia V Stan, Yuchen Sun Understanding dynamic fragmentation in shock-loaded metals and studying the resulting high-velocity microjets is of considerable importance for applied sciences and engineering applications. The current work presents hydrodynamic simulations of laser-driven microjetting from micron-scale grooves on a tin surface. The simulations supported designing experiments on the OMEGA and OMEGA-EP lasers. Microjet formation is investigated for 3-120 GPa shock pressures, from drives spanning solid on release to melting the target. We examine the effect of variations in target geometry for solid, liquid, and partially melted tin microjets. Model predictions are compared to recent experiments containing geometry and drive variations. Finally, we perform scaling studies of jet formation in the experimental configuration in an effort to link jetting in mm-scale laser experiments with cm-scale gas gun configurations. |
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