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A new approach for performing quantitative structure-factor analysis and density measurements of liquids using X-ray diffraction with a pink-spectrum X-ray source is described. The methodology corrects for the pink beam effect by performing a Taylor series expansion of the diffraction signal. The mean density, background scale factor, peak X-ray energy about which the expansion is performed, and the cutoff radius for density measurement are estimated using the derivative-free optimization scheme. The formalism is demonstrated for a simulated radial distribution function for tin. Finally, the proposed methodology is applied to experimental data on shock compressed tin recorded at the Dynamic Compression Sector at the Advanced Photon Source, with derived densities comparing favorably with other experimental results and the equations of state of tin. [ABSTRACT FROM AUTHOR]

Shock compression experiments on natural compositions are imperative to accurately model planetary accretion and the interior dynamics of planets. Combining shock compression experiments from the Sandia Z Machine and the OMEGA EP laser facility with density functional theory‐based molecular dynamics calculations, we report the first pressure‐density‐temperature (P‐ρ‐T) relationship of natural iron (Fe)‐bearing olivine ((Mg0.91Fe0.09)2SiO4) on the principal Hugoniot between 166 and 1,465 GPa. Additionally, we report the first reflectivities of natural olivine liquid in this pressure range. Compared to the magnesium‐endmember forsterite (Mg2SiO4), the presence of Fe in typical mantle abundance (∼9 wt% FeO) alters the US‐uP relation of olivine. On the other hand, the shock temperature and reflectivity of olivine are indistinguishable from forsterite where experimental conditions overlap. Both forsterite and olivine increase in reflectivity (and hence optical conductivity) with increasing temperature, with a maximum reflectivity of ∼31% at shock velocities greater than 22 km/s (∼800 GPa). Plain Language Summary: Olivine is the most abundant mineral in Earth's upper mantle and in the mantles of other rocky bodies in the Solar System. While previous studies of this material have focused on iron‐free compositions, natural olivine contains varying amounts of iron. The data presented here describe how olivine responds to shock waves, which are important for understanding the outcomes of collisions onto growing planets. With these data, we can more robustly model the pressure and temperature conditions reached in impact situations, as well as the relative amounts of melting and vaporization that will occur from an impact. These parameters are key to understanding the chemistry that can occur as planets grow. We have also found that olivine liquid becomes highly reflective at high temperatures, which suggests that it is electrically conductive. This observation is important for understanding the generation of magnetic fields in very hot or molten planets. Key Points: Combined dynamic compression data with computations to define the pressure‐density‐temperature relation on the Hugoniot of olivineThe principal Hugoniot of olivine diverges from Fe‐free forsterite over the experimental conditionsOlivine liquid is optically conductive at high temperatures and high pressures [ABSTRACT FROM AUTHOR]

Ferroelectric materials under shock compression can generate current and power by a drastic change of the remnant polarizations and surface bound charge. This behavior has been employed in applications involving nuclear fusion trigger, energy storage devices, and high pulse power sources. Despite the large power output in lead‐containing ferroelectrics, lead‐free materials are highly desirable owing to the environmental concerns. Herein, the phase transition behaviors and current outputs of 0.92Bi0.5Na0.5TiO3‐0.08BiAlO3 (BNT‐8BA) materials are studied under high pressure. The BNT‐8BA ferroelectric ceramics can be completely depolarized from polar to the nonpolar state under shock compression, resulting in a current output in the external circuit. The phase‐transition‐induced depolarization pressures of BNT‐8BA are lower than those of the pure Bi0.5Na0.5TiO3 under both dynamic and static high‐pressure loads. These results can allow the understanding of the high‐pressure behavior of BNT‐8BA for application as ferroelectric pulsed power supply. [ABSTRACT FROM AUTHOR]

The response of forsterite, Mg2SiO4, under dynamic compression is of fundamental importance for understanding its phase transformations and high‐pressure behavior. Here, we have carried out an in situ X‐ray diffraction study of laser‐shocked polycrystalline and single‐crystal forsterite (a‐, b‐, and c‐orientations) from 19 to 122 GPa using the Matter in Extreme Conditions end‐station of the Linac Coherent Light Source. Under laser‐based shock loading, forsterite does not transform to the high‐pressure equilibrium assemblage of MgSiO3 bridgmanite and MgO periclase, as has been suggested previously. Instead, we observe forsterite and forsterite III, a metastable polymorph of Mg2SiO4, coexisting in a mixed‐phase region from 33 to 75 GPa for both polycrystalline and single‐crystal samples. Densities inferred from X‐ray diffraction data are consistent with earlier gas‐gun shock data. At higher stress, the response is sample‐dependent. Polycrystalline samples undergo amorphization above 79 GPa. For [010]‐ and [001]‐oriented crystals, a mixture of crystalline and amorphous material is observed to 108 GPa, whereas the [100]‐oriented forsterite adopts an unknown phase at 122 GPa. The first two sharp diffraction peaks of amorphous Mg2SiO4 show a similar trend with compression as those observed for MgSiO3 in both recent static‐ and laser‐driven shock experiments. Upon release to ambient pressure, all samples retain or revert to forsterite with evidence for amorphous material also present in some cases. This study demonstrates the utility of femtosecond free‐electron laser X‐ray sources for probing the temporal evolution of high‐pressure silicate structures through the nanosecond‐scale events of shock compression and release. Key Points: The phases occurring along the Hugoniots of forsterite are identified from 19 to 122 GPaBetween 33 and 75 GPa, forsterite and forsterite III coexist for both single‐crystal and polycrystalline samplesAt higher shock stress, variable degrees of amorphization are observed with different onset stresses for polycrystals and single crystals [ABSTRACT FROM AUTHOR]

The combination of high‐power laser and synchrotron X‐ray pulses allows us to observe material responses under shock compression and release states at the crystal structure on a nanosecond time scale. A higher‐power Nd:glass laser system for laser shock experiments was installed as a shock driving source at the NW14A beamline of PF‐AR, KEK, Japan. It had a maximum pulse energy of 16 J, a pulse duration of 12 ns and a flat‐top intensity profile on the target position. The shock‐induced deformation dynamics of polycrystalline aluminium was investigated using synchrotron‐based time‐resolved X‐ray diffraction (XRD) under laser‐induced shock. The shock pressure reached up to about 17 GPa with a strain rate of at least 4.6 × 107 s–1 and remained there for nanoseconds. The plastic deformation caused by the shock‐wave loading led to crystallite fragmentation. The preferred orientation of the polycrystalline aluminium remained essentially unchanged during the shock compression and release processes in this strain rate. The newly established time‐resolved XRD experimental system can provide useful information for understanding the complex dynamic compression and release behaviors. [ABSTRACT FROM AUTHOR]

We describe studies of shock initiation and shock‐to‐detonation transitions in energetic materials using a tabletop shock compression microscope with nanosecond time resolution and micrometer spatial resolution. Planar input shocks with durations of 4–20 ns are produced using 0–4.5 km/s laser‐launched flyer plates. Emphasis is on measurements of temperature, velocities, pressure, and microstructure using photon Doppler velocimetry (PDV), optical pyrometry and high‐speed videography. Techniques are discussed for fabricating disposable shock target arrays of tiny plastic‐bonded explosives (PBX), liquid and powder explosives, and single‐crystal explosives for high‐throughput studies. Optical temperature measurements of shocked triaminotrinitrobenzene (TATB) are discussed. Since TATB is yellow, we developed methods to correct for the blue absorption to obtain more accurate temperatures. Hot spots in shocked polymer‐encased HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) crystals are observed in real‐time, showing a hot spot produced in a collapsing void that ignites a deflagration. Despite the small dimensions of our explosive charges (typically 1 mm diameter and 250 μm length), we produced reproducible detonation states in solid and liquid explosives using short‐duration shocks near the von Neumann spike (VNS) pressure. We show the VNS pressure is associated with a transition to high‐efficiency gas production from the explosives. In studies of NM, prior to detonation, we see reaction originating at hot spots which coalesce to form a superdetonation. [ABSTRACT FROM AUTHOR]

In situ X‐ray diffraction with advanced X‐ray sources offers unique opportunities for investigating materials properties under extreme conditions such as shock‐wave loading. Here, Singh's theory for deducing high‐pressure density and strength from two‐dimensional (2D) diffraction patterns is rigorously examined with large‐scale molecular dynamics simulations of isothermal compression and shock‐wave compression. Two representative solids are explored: nanocrystalline Ta and diamond. Analysis of simulated 2D X‐ray diffraction patterns is compared against direct molecular dynamics simulation results. Singh's method is highly accurate for density measurement (within 1%) and reasonable for strength measurement (within 10%), and can be used for such measurements on nanocrystalline and polycrystalline solids under extreme conditions (e.g. in the megabar regime). A methodology of deducing strength and density of polycrystalline tantalum and diamond under extreme compression conditions from two‐dimensional X‐ray diffraction patterns is examined rigorously with large‐scale molecular dynamics and X‐ray diffraction simulations. [ABSTRACT FROM AUTHOR]

Time‐resolved X‐ray diffraction measurements have been carried out on dynamically compressed Sn up to a maximum pressure of ∼13 GPa at the European Synchrotron Radiation Facility. The phase transition from β‐Sn to body‐centered tetragonal (b.c.t.) Sn has been observed using synchrotron X‐ray diffraction for the first time undergoing shock compression and release. Following maximum compression, the sample releases to lower pressures for several nanoseconds until the reverse transition occurs. The data are in good agreement with previous shock boundaries that indicate that the β‐Sn phase is stable ∼2 GPa higher than the static boundary upon compression and the b.c.t.‐Sn phase is stable ∼1 GPa lower upon release. The transition to the high‐pressure phase reveals a loss of texture in the X‐ray diffraction data from the 'quasi' single‐crystal β‐Sn structure to a more powder‐like Debye–Scherrer ring. Time‐resolved X‐ray diffraction measurements were carried out on dynamically compressed Sn at the ID09 beamline of the European Synchrotron Radiation Facility. Using an infra‐red laser (up to 180 mJ at 1064 nm) with a 5 ns Gaussian pulse shape, the high‐pressure β‐Sn to b.c.t.‐Sn phase transition was observed using a single X‐ray bunch from the synchrotron. [ABSTRACT FROM AUTHOR]

Abstract: Shockwave data on mineral‐forming compounds such as Mg2SiO4 are essential for understanding the interiors of Earth and other planets, but correct interpretation of these data depends on knowing the phase assemblage being probed at high pressure. Hence, direct observations of the phase or phases making up the measured states along the forsterite Hugoniot are essential to assess whether kinetic factors inhibit the achievement of the expected equilibrium, phase‐separated assemblage. Previous shock recovery experiments on forsterite, which has orthorhombic space group Pbnm, show discrepant results as to whether forsterite undergoes segregation into its equilibrium phase assemblage of compositionally distinct structures upon shock compression. Here we present the results of plate impact experiments on polycrystalline forsterite conducted at the Dynamic Compression Sector of the Advanced Photon Source. In situ X‐ray diffraction measurements were used to probe the crystal structure(s) in the shock state and to investigate potential decomposition into periclase and bridgmanite. In contrast to previous interpretations of the forsterite shock Hugoniot, we find that forsterite does not decompose but instead reaches the forsterite III structure, which is a metastable structure of Mg2SiO4 with orthorhombic space group Cmc21. [ABSTRACT FROM AUTHOR]

Forsterite (Mg2SiO4) single crystals were shock compressed to pressures between 200 and 950 GPa using independent plate-impact steady shocks and laser-driven decaying shock compression experiments. Additionally, we performed density functional theory-based molecular dynamics to aid interpretation of the experimental data and to investigate possible phase transformations and phase separations along the Hugoniot. We show that the experimentally obtained Hugoniot cannot distinguish between a pure liquid Mg2SiO4 and an assemblage of solid MgO plus liquid magnesium silicate. The measured reflectivity is nonzero and increases with pressure, which implies that the liquid is a poor electrical conductor at low pressures and that the conductivity increases with pressure. [ABSTRACT FROM AUTHOR]

The microscopic and dynamic response of the atactic polystyrene molecules under shock compression at laser power density of 4.9 GW/cm2 was studied using time-resolved Raman spectroscopy. The shock pressure estimated in the polystyrene sample was 2 GPa, and the temporal and wavenumber resolutions in these experiments were 3 ns and 3 cm−1, respectively. The shocked polystyrene showed a blue shift of 5 and 7 cm−1 for the 1004 cm−1 (C-C-C ring bending mode ν12) and 1606 cm−1 (C-C ring stretching mode [ABSTRACT FROM AUTHOR]

The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits). [ABSTRACT FROM AUTHOR]

Shock compression of finely ground CaF2 crystals embedded into graphite powder in cylindrical recovery ampoules was found to yield single white crystals of 0.1 mm in size within the Mach cone, where the developed temperatures/pressures are exeedingly high. The composition of these crystals CaO ⋅ 3SiO2 ⋅ SiC is a result of chemical interactions of mixture and SiO2 due to cumulative eruption of Si from steel walls of ampoules and its reaction with O2 from sample pores. The atomic structure of crystals was characterized by IR spectroscopy and XRD. The formation of relatively large single crystals can take place only in the melted unloaded material. [ABSTRACT FROM AUTHOR]

PZT‐5H piezoelectric ceramic has been recommended for instrument applications for many years. Their dynamic piezoelectric properties under shock compression are worthy of attention in various applications. In order to study the dynamic piezoelectric characteristics of PZT‐5H under impact compression, the impact compression experiments are carried out about the PZT‐5H samples with different thickness by using SHPB as loading system, the impact pressure and the electrical output measurement systems are designed by the authors. Through the impact experiments, discharge voltage and stress are measured to explore the relationship between the axial dynamic piezoelectric voltage constant and the stress pulse. The results indicate that whether quasi‐static or dynamic, the PZT‐5H has a yield stress of approximately 150 MPa. The axial piezoelectric voltage constant of PZT‐5H under shock compression is not a constant but a function of stress, even in the elastic region. In the elastic region, the relationship between the axial piezoelectric voltage constant and the stress is exponentially distributed, while in the plastic region it is linearly distributed. The plastic deformation of the material under stress causes the axial piezoelectric voltage constant of PZT‐5H to decrease continuously. Due to the ferroelectricity of PZT‐5H, the discharge voltage increases inversely after the stress unloading. The impact compression experiments are carried out about different thicknesses of PZT‐5H samples with SHPB as the loading system to study the dynamic piezoelectric properties of the samples under impact compression. Through the impact experiments, discharge voltage and stress are measured to explore the relationship between the axial dynamic piezoelectric voltage constant and the stress pulse. [ABSTRACT FROM AUTHOR]