Hugoniot EOS measurements at Mbar pressures

Abstract

The AWE HELEN laser is being used to measure high-pressure Hugoniot data by the impedance match method. Indirect drive is used to generate pressures of up to 10 Mbar in the aluminum reference material. We are aiming to measure shock velocities in our targets to ± 1 %, leading to errors in pressure and particle velocity of the order of ±2%. This requires improvements in target fabrication and characterization, streak camera calibration and data analysis, coupled with investigations into shock planarity and attenuation. Our latest results have accuracies of 2–4% in shock velocity but have identified work that should allow us to achieve our intended level of accuracy. Experiments have been done with copper and chlorinated plastic; our results are compared with theory, and, for copper, with U.S. and Russian gas-gun, explosively or nuclear-driven experiments.

A review of astrophysics experiments on intense lasers

“…The experiments (57,60,61) suggest that on the Jovian isentrope molecular hydrogen probably begins to dissociate at 400 kbar and dissociation continues smoothly to completion at -3 Mbar, with metallization occurring right in the middle of this region at -1.4 Mbar and -4000 K. It now seems likely (60) that currents near the surface of Jupiter, at radii out to 0.95R, contribute to the surface magnetic field, whereas previously it was thought that the magnetic field was formed deeper in the interior at -0.75 R,. The EOS of astrophysically relevant materials are bein, 0 measured on other lasers as well, including LULI (62), Vulcan (62,63), Helen (60,64), Astrix (65), Gekko (66), and Shenguang-I (67). This whole area of measuring high pressure EOS on intense lasers represents fertile new territory for planetary and astrophysics research.…”

Approaching the “cold curve” in laser-driven shock wave experiment of a matter precompressed by a partially perforated diamond anvil

“…The setup presented in Figure 2 is designed for measuring the properties of an opaque sample material who's EOS is known up to the precompression pressure. The sample material is located on top of a "shock standard" material who's EOS is known in a wide thermodynamic range (Al for example (Evans et al, 1996;Lomonosov, 2007;Pickard & Needs, 2010)) and the shock velocity through it was measured and calibrated to the driven laser parameters in a preliminary experiment. The rest of the sample volume is filled with a transparent fluid acting as a pressure medium for the precompression stage and as a window for the shock stage of the experiment.…”

Preparation of Mo–Mo step by vacuum bond

“…Equation of state (EOS) study at high pressure is physically important in laser inertial confinement fusion (ICF) [1][2][3][4][5]. The typical method for determining EOS points is based on the impedance-matching technique by measuring the shock velocity simultaneously using a double-step target.…”