Relative Consistency of Equations of State by Laser Driven Shock Waves

Abstract

An experiment shows that equations of state of solid matter at pressure P= 10–50 Mbar can be studied by using lasers with pulse energy E≈100J. Laser beams smoothed by phase-zone plates produced high quality, planar shock waves in two-step, two-material targets, allowing simultaneous measurements of the shock velocities in the two materials. By the use of the impedance-matching technique, the relative consistency of the equations of state of these materials can be tested, or a relative equation of state data can be measured. Pressures higher than 35 Mbar were achieved in gold

Equation of State Data for Iron at Pressures beyond 10 Mbar

“…Hence, by considering that the Al-Fe interface is in dynamic equilibrium, and by applying the conditions for shock transmission into a denser material (impedance mismatch), it is possible to obtain an EOS point for iron, once the shock velocity D Fe is measured. This is a classical method in EOS experiments, described in textbooks [32] and used with conventional methods of dynamic compression and more recently with laser-driven shock waves [24]. The scheme of the experimental setup is shown in Fig.…”

“…Recently, laser-driven shocks have become a reliable tool in high pressure physics thanks to developments in control of uniformity, steadiness, and preheating [24][25][26][27], and have been used for EOS measurements of deuterium [28], copper [29], plastic [30], and gold [31].…”

“…The experiment.-The experiment uses the impedance mismatch method [24,32] based on the simultaneous measurement of the shock velocity D in two different materials. The first one is the material with unknown EOS (iron in our case), while the second one is a reference material; we have chosen aluminum, because its EOS is well known at high pressures [23].…”

Novel diagnostic of low-Z shock compressed material

“…While a few experiments have used X-ray radiography on low-Z materials to determine both velocities [3], most of them [4,5] rely on the shock velocities measurement (via optical interferometry in transparent media or by observation of shock breakout times on steps of known thickness in optically opaque materials). The latter technique results in indirect EOS determinations through a method known as impedance matching.…”

Time evolution of electron structure in femtosecond heated warm dense molybdenum

“…The data indicate a highly nonequilibrated state, 5 ps after heating. The study of Warm Dense Matter (WDM) shows a strong renewed interest, due to advances in transient techniques to create matter in this regime [1][2][3][4][5][6] , and in first principles calculations to simulate the physical properties 7,8 involved in various physical domains such as planetary physics 9 , inertial confinement fusion 10 , and applied laser processes 11 . The difficulty of modeling comes from the atomic level: disordered matter, partially degenerate electrons and strongly coupled ions.…”