Review of experimental techniques for high rate deformation and shock studies

With the advent of high-energy-density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, millimeter-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly suitable to this class of experimental astrophysics include the study of opacities relevant to stellar interiors, equations of state relevant to planetary interiors, strong shock-driven nonlinear hydrodynamics and radiative dynamics relevant to supernova explosions and subsequent evolution, protostellar jets and high Mach number flows, radiatively driven molecular clouds and nonlinear photoevaporation front dynamics, and photoionized plasmas relevant to accretion disks around compact objects such as black holes and neutron stars.

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Experimental astrophysics with high power lasers and Z pinches

▪ Abstract We know that giant planets played a crucial role in the making of our Solar System. The discovery of giant planets orbiting other stars is a formidable opportunity to learn more about these objects, what their composition is, how various processes influence their structure and evolution, and most importantly how they form. Jupiter, Saturn, Uranus, and Neptune can be studied in detail, mostly from close spacecraft flybys. We can infer that they are all enriched in heavy elements compared to the Sun, with the relative global enrichments increasing with distance to the Sun. We can also infer that they possess dense cores of varied masses. The intercomparison of presently characterized extrasolar giant planets shows that they are also mainly made of hydrogen and helium, but that they either have significantly different amounts of heavy elements, have had different orbital evolutions, or both. Hence, many questions remain and need to be answered to make significant progress on the origins of planets...

THE INTERIORS OF GIANT PLANETS: Models and Outstanding Questions

Hydrogen and helium are the most abundant elements in the Universe. They are also, in principle, the most simple. Nonetheless, they display remarkable properties under extreme conditions of pressure and temperature that have fascinated theoreticians and experimentalists for over a century. Advances in computational methods have made it possible to elucidate ever more of their properties. Some of these methods that have been applied in recent years, in particular, those that perform simulations directly from the physical picture of electrons and ions, such as density functional theory and quantum Monte Carlo are reviewed. The predictions from such methods as applied to the phase diagram of hydrogen, with particular focus on the solid phases and the liquid-liquid transition are discussed. The predictions of ordered quantum states, including the possibilities of a low- or zero-temperature quantum fluid and high-temperature superconductivity are also considered. Finally, pure helium and hydrogen-helium mixtures, the latter which has particular relevance to planetary physics, are discussed.

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The properties of hydrogen and helium under extreme conditions

Recently, deuterium has been the focus of a high level of experimental and theoretical activity, sparked by a disagreement on the experimental value of the maximum compression along the principal Hugoniot. The behavior of deuterium at megabar pressures is not well understood. It is of great interest to understand how the current uncertainty on the hydrogen/deuterium equation of state (EOS) affects the inferred structures of Jupiter and Saturn. In particular, the mass of a core of heavy elements (other than H and He) and the total mass of those heavy elements in these two planets are quite sensitive to the EOS of hydrogen and constitute important clues to their formation process. We present a study of the range of structures allowed for Jupiter and Saturn by the current uncertainty in the hydrogen EOS and astrophysical observations of the two planets. An improved experimental understanding of hydrogen at megabar pressures and better determinations of the gravitational moments of both planets are necessary to put tight bounds on their internal structure.

https://iopscience.iop.org/article/10.1086/421257/pdf

Shock Compression of Deuterium and the Interiors of Jupiter and Saturn

Hugoniot points of liquid ${\mathrm{D}}_{2}$ were measured at shock pressures of 107, 54, and $28\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ using converging explosively driven systems (CSs). The two data sets measured with a laser $(L)$ and pulsed currents (PCs) differ substantially. Our results are in excellent agreement with the PC data and the error bars of the CS-PC data are less than half those of the $L$ data. The limiting compression obtained from the best fit to the CS-PC data is $4.30\ifmmode\pm\else\textpm\fi{}0.10$ at $100\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The CS-PC data are in good agreement with path integral Monte Carlo and density functional theory calculations, which is expected to be the case at even higher shock temperatures and pressures, as well.

Shock compression of liquid deuterium up to 109 GPa

Experimental data on the compression of solid deuterium at a pressure of ∼60 GPa are presented. The data were obtained on a generator of powerful converging spherical shock waves. The results are compared with the data of shock experiments obtained on a Nova laser facility and an electrodynamic EPBF-Z plant.

Shock compression of solid deuterium

Shock-wave compression of solid deuterium at a pressure of 120 GPa

In the mid-1950s, experimental studies of condensed matter at extremely high pressures (i.e., high energy densities) started to appear in the scientific literature, made possible by using strong shock waves to influence intensively the state of the substance being studied. Russian Federal Nuclear Centres in Sarov and Snezhinsk and their Academy of Sciences counterparts in Moscow, Chernogolovka, and Novosibirsk were instrumental in developing dynamic measurement techniques and forming this new line of investigation of extreme states of matter, based on application of shock waves in high-pressure physics.

http://iopscience.iop.org/article/10.1070/PU1999v042n03ABEH000545/pdf

Development of dynamic high-pressure techniques in Russia

We review the results of shock compression of solid protium to the pressure 66 GPa, of liquid deuterium to 110 GPa, and of solid deuterium to 123 GPa in explosive devices of spherical geometry. The results are compared with data obtained by US scientists using traditional energy sources (explosives and light-gas guns), striker acceleration in a strong magnetic field (Z facility at Sandia), and powerful lasers (Nova at Lawrence Livermore National Laboratory (LLNL) and Omega at the Laboratory for Laser Energetics, University of Rochester). Results of density measurements of hydrogen isotopes under quasi-isentropic compression are analyzed. The absence of an anomalous increase in density under shock and quasi-isentropic compression of hydrogen isotopes is demonstrated. On the other hand, both processes exhibit a sharp change in the compression curve slopes, at the respective pressures 45 and 300 GPa.

https://iopscience.iop.org/article/10.3367/UFNe.0180.201006d.0605/pdf

V. D. Urlin

Papers

Shock compression of liquid deuterium up to 109 GPa

Shock compression of solid deuterium

Shock-wave compression of solid deuterium at a pressure of 120 GPa

Development of dynamic high-pressure techniques in Russia

Dynamic compression of hydrogen isotopes at megabar pressures