Hugoniot and spall data from the laser-driven miniflyer

Abstract

The laser-driven minitlyer has been developed as a small-sized complement to the propellant-or gasdriven gun with which to make material property measurements, Flyer velocities typically range from 0,5 to 1.5 km/s, depending on the energy of the launching laser and the flyer dimensions.The I G50~m-thick flyers, I--3 mm in diameter, and comparably small targets require very little material and are easy to recover for post-experiment analysis, To measure and irr,prove the precision of our measurements, we ase conducting an extensive series of experiments impacting well-characterized Cu, Al, and Au on several transparent, calibrated, windows (PMMA, LiF, and sapphire). Measurement of the impact and interface velocities with a high-time-resolution velocity interferometer (V ISAR) gives us a point on the Hugoniot of the flyer material.These are then compared to published Hugoniot data taken with conventional techniques.In the span experiments, a flyer strikes a somewhat thicker target of the same material and creates a span in the target. Measuring the free-surface velocity of the target gives information on the compressive elastic-plastic response of the target to the impact, the tensile span strength, and the strain rate at which the span occurred. Volumetric strain rates al span in these experiments are frequently in the 106-108 s-' range, considerably higher than the 103-104 s-' range obtainable from gas gun experiments,

Confined plasma ablation for shock physics, plate launch, and material dynamics

“…Dynamic spall strength of materials, and equation-of-state (EOS) have been determined using laser-launched flyer plates. 8,9,10 …”

Use of laser-accelerated foils for impact study of dynamic material behaviour

“…The laser pulse is focused onto the surface of an aluminium foil of thickness ranging from 50 to 500 mm. The thickness of the vapourized layer can be neglected with respect to this initial thickness [3,7], like in similar studies involving 12-120 mm-thick flyers [1,4,8]. To increase the impulse momentum delivered by the laser-matter interaction, the plasma is confined by a water layer covering the irradiated surface.…”

“…This shock wave generator, sometimes called laser gun, or laser-driven miniflyer, has been widely used to study the shock initiation of condensed explosives [1,2], where varying and controlling the peak pressure and its time of application are key issues. Considering the small dimensions involved (of millimetreorder), the low cost of laser shots and their high repetition rate, such impacts can also be used to investigate the response of solid materials to shock loading [3][4][5], as an alternative technique to the conventional plate impact tests, involving heavier apparatus such as gas guns. However, potential problems like projectile planarity before impact, which has been shown to depend critically on the spatial uniformity of the laser pulse [6], accurate control of the projectile velocity, or influence of the air layer compressed between the flyer and target should be addressed to obtain useful experimental data.…”

Laser-induced shock waves in condensed matter: some techniques and applications

“…In laser-launched flyer-plate loading [9,18], u fp and u p at the flyer-window interface during impact can be measured from a single shot (Fig. 3).…”