Dynamic compression of materials: metallization of fluid hydrogen at high pressures

Abstract

Dynamic high pressure is 1 GPa (10 kbar) or greater with a rise time and a duration ranging from 1 ps (10 −12 s) to 1 µs (10 −6 s). Today it is possible in a laboratory to achieve pressures dynamically up to ∼500 GPa (5 Mbar) and greater, compressions as much as ∼15fold greater than initial density in the case of hydrogen and temperatures from ∼0.1 up to several electronvolts (11 600 K). At these conditions materials are extremely condensed semiconductors or degenerate metals. Temperature can be tuned independently of pressure by a combination of shock and isentropic compression. As a result, new opportunities are now available in condensed matter physics at extreme conditions. The basic physics of the dynamic process, experimental methods of generating and diagnosing matter at these extreme conditions and a technique to recover metastable materials intact from ∼100 GPa shock pressures are discussed.Results include (i) generation of pressure standards at static pressures up to ∼200 GPa (2 Mbar) at 300 K, (ii) single-shock compression of small-molecular fluids, including resolution of the recent controversy over the correct shock-compression curve of liquid D 2 at 100 GPa pressures, (iii) the first observations of metallization of fluid hydrogen, nitrogen and oxygen compressed quasi-isentropically at 100 GPa pressures, (iv) implications for the interiors of giant planets within our solar system, extrasolar giant planets and brown dwarfs discovered recently and the equation of state of deuterium-tritium in inertial confinement fusion (ICF) and (v) prospects of recovering novel materials from extreme conditions, such as metastable solid metallic hydrogen. Future research is suggested.

High energy density physics studies using intense particle beams at the FAIR facility at Darmstadt

“…Simulations have shown that using the SIS100 parameters, it is possible to compress solid hydrogen to a density of about 3g/cm 3 having a pressure of the order of 30 Mbar while the temperature remains low (about 10000 K) which are conditions expected at the interiors of the Gaint palnets. This experiment can also help to understand hydrogen metallization [10] problem.…”

Metal-Dielectric Transition in Hydrogen

“…We assume that, when metallic hydrogen is produced, the molecular phase of liquid hydrogen transforms into the atomic phase [9] and only some atoms are later ionized.…”

“…A qualitative breakthrough in the studies of metallic hydrogen occurred after a number of experiments on shock compression of both molecular hydrogen in the liquid state and hydrogen and deuterium plasma. Those experiments showed that electric conductivity increased steeply for certain combinations of density, pressure, and temperature [4][5][6][7][8][9]. Specific values of these parameters depended on the initial state of hydrogen (i.e., the state before compression).…”

Single-mode fiber, velocity interferometry

“…Material-strength changes and phase transitions occur on nanosecond time scales in impact experiments -on these short time scales, the response of materials can be remarkably different than expected when compared to slower loading. The different macroscopic dynamics observed under high load rates has inspired theories that attempt to predict the underlying rates of microscopic mechanisms responsible for the observed differences in behavior (for recent reviews, see [1][2][3][4][5]). …”

“…Mass velocities up to a few km/s are generated in single-shock, propellant-driven, flier-plate impact experiments [1][2][3]. Higher velocities have been generated in pulsed-laser and pulsed-plasma driven experiments up to 19 km/s [6], 30 km/s [4], and ~ 100 km/s [5]. Improving the temporal and velocity resolution of high-velocity measurements continues to be of interest as it will lead to improved data needed to better understand high strain rate processes.…”