We have used x-ray diffraction with subnanosecond temporal resolution to measure the lattice parameters of orthogonal planes in shock compressed single crystals of silicon (Si) and copper (Cu). Despite uniaxial compression along the (400) direction of Si reducing the lattice spacing by nearly 11%, no observable changes occur in planes with normals orthogonal to the shock propagation direction. In contrast, shocked Cu shows prompt hydrostaticlike compression. These results are consistent with simple estimates of plastic strain rates based on dislocation velocity data.
The TRIDENT laser was used to launch Cu, Ga, and NiTi flyers from poly(methylmethacrylate) (PMMA) substrates, coated with thin (∼micron) layers to absorb the laser energy, confine the plasma, and insulate the flyer. The laser pulse was ∼600ns long, and the flyers were 50 to 250μm thick and 4 mm in diameter. With an energy of 10–20 J, speeds of several hundred meters per second were obtained. Simulations were performed of the flyer launch process, using different models. The simulations reproduced the magnitude of the flyer speed and qualitative variations with drive energy and design parameters, but systematically overpredicted the flyer speed. The most likely explanation is that some of the laser energy was deposited in the transparent substrate, reducing the amount available for acceleration. The deceleration of the flyer was measured on impact with a PMMA window. Given the equation of state and optical properties of PMMA, the deceleration allowed points to be deduced on the principal Hugoniot of Cu. The points deduced were in good agreement with the published equation of state for Cu, suggesting that there was no significant preheating of the flyer or other systematic effects which might reduce the accuracy of equation of state measurements.
We present validation and some applications of two laser-driven shock wave loading techniques: laser-launched flyer plate and confined laser ablation. We characterize the flyer plate during flight and the dynamically loaded target with temporally and spatially resolved diagnostics. With transient imaging displacement interferometry, we demonstrate that the planarity (bow and tilt) of the loading induced by a spatially shaped laser pulse is within 2-7 mrad (with an average of 4+/-1 mrad), similar to that in conventional techniques including gas gun loading. Plasma heating of target is negligible, in particular, when a plasma shield is adopted. For flyer plate loading, supported shock waves can be achieved. Temporal shaping of the drive pulse in confined laser ablation allows for flexible loading, e.g., quasi-isentropic, Taylor-wave, and off-Hugoniot loading. These techniques can be utilized to investigate such dynamic responses of materials as Hugoniot elastic limit, plasticity, spall, shock roughness, equation of state, phase transition, and metallurgical characteristics of shock-recovered samples.
Laser-induced shock waves in condensed matter have important applications in dynamic material studies and high pressure physics. We briefly review some techniques in laser-induced shock waves, including direct laser drive, laser-launched flyer plate, quasi-isentropic loading, point and line imaging velocity interferometry, transient X-ray diffraction, spectroscopy and shock recovery, and their applications to study of equation of state, spallation, and phase transitions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.