Polycrystalline samples of anthracene, phenanthrene, and pyrene have been stressed with shock waves to pressures of 550 kbar. States in the stressed samples were determined by measuring shock wave velocities in the samples and in an 1100 aluminum base plate used as a standard. An abrupt increase in the compressibility was noted for each material: it occurred at 176 kbar for anthracene, 201 kbar for phenanthrene, and 234 kbar for pyrene. This increase is believed to be associated with an intermolecular coupling reaction. Recovered samples of anthracene did exhibit this coupled structure. The Hugoniot and calculated isotherm both indicate that anthracene is more compressible than was previously thought. The equation of state of 1100 aluminum was determined during this work.
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The Hugoniot of solid argon (initially at 75°K and approximately 1 bar) has been determined using standard shock-wave techniques. Sample pressures ranged 18–645 kbar with associated densities of 1.39–2.18 times the initial density of 1.65 g/cc. Utilizing an exp-6 interatomic potential, a computed fit was obtained which was in excellent agreement with the data up to 300 kbar. The deviation between theoretical and experimental Hugoniot above 300 kbar is interpreted as either due to melting or to an inadequate model and potential form.
A solid-to-solid phase transition has been induced in antimony by an explosive-produced shock wave of about 130 kbar. Details of the transition were determined by measurement of the free—surface motion with electrical pin contactors. The first plastic wave pressure varied from 108 kbar for the thinnest samples to 91 kbar for the thickest samples. This variation is felt to be due to the sluggishness of the transition, the material requiring about 0.6 μsec to relax into its higher-density phase. The transition pressure was found to be 88 kbar. Hugoniot data are presented in conjunction with existing higher-pressure dynamic data.
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,
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