We have performed in situ time-resolved x-ray diffraction at 100 GPa on laser-shocked CaSiO3 glass to investigate the glass-to-crystal transition. At this extreme pressure, we observe the ultrafast crystallization of the CaSiO3 perovskite structure from the compressed amorphous phase, with a typical nucleation time of 1.69 f 0.10 ns and a final grain size of 20 nm. The grain size temporal evolution suggests a diffusion-controlled transformation. Moreover, the observed concomitant explosive grain growth together with the release wave arrival into shocked CaSiO3 also suggests a role of the release in the nucleation process.

Ni40Co20Fe10Cr10Al18W2 additively manufactured using laser powder bed fusion (LPBF) is among the toughest as-built alloys reported and is a promising candidate for use in extreme environments. However, its behavior under multi-megabar pressure regimes remains unexplored. We used femtosecond in situ X-ray diffraction to investigate the shock response of LPBF Ni40Co20Fe10Cr10Al18W2 under laser-driven shock compression and release. Our results reveal that the initial dual-phase face-centered + body-centered structure transforms to a single face-centered phase over a wide pressure range of 84 +/- 11 to 277 +/- 56 GPa, followed by a transition to a single body-centered phase at 431 +/- 57 GPa. We establish the Hugoniot equation-of-state of LPBF Ni40Co20Fe10Cr10Al18W2 and compare it to the benchmark alloy LPBF AlCoCrFeNi2.1, demonstrating the effects of Wdoping and increased Al content. High stacking fault probabilities, close to those measured in Au and Ag, are observed upon compression. A portion of the stacking faults are annihilated upon release to ambient pressure.

Abstract Nanowire arrays are excellent nanostructured target materials for high-energy density (HED) science and applications because of their enhanced energy absorption properties. However, investigations of the spatiotemporal dynamics of laser-irradiated nanowire arrays remain limited, since conventional time-resolved diagnostics cannot capture the rapid plasma-state transitions. This study reports spatiotemporally resolved measurements of laser energy absorption and electron transport in laser-irradiated nanowire arrays using an X-ray free-electron laser (XFEL). The XFEL measurements showed that the nanowire array is promptly heated to an electron temperature of ~ 120 eV at the main-pulse interaction peak, followed by a further increase to ~ 140 eV around 10 ps, which was associated with wire collapse. The experimental results also confirmed that further enlargement of the heated area was suppressed by the restricted electron transport in nanowire arrays. These observations advance our understanding of HED plasma formation and evolution within the laser-irradiated nanowire arrays, laying a foundation for various applications.

Abstract Serpentine is a major hydrous mineral present in hydrous asteroids that have evolved through planetary impacts. Understanding its dynamic behavior is essential to elucidate the redistribution and retention of water during high‐velocity impact processes. The shock response of antigorite was examined at pressures up to 106 GPa using laser‐driven shock compression combined with ultrafast time‐resolved X‐ray diffraction measurements. Results show that shock‐compressed antigorite remained crystalline up to 44 GPa (impact velocity ∼4.7 km/s), whereas it transformed to an amorphous state above 66 GPa (∼6.4 km/s). This transformation was completed within a few nanoseconds during compression, and recrystallization from the amorphous state did not occur during subsequent decompression, indicating that shock‐induced amorphization is the dominant structural response of antigorite. Adiabatic release calculations further indicate that the decompression path of shocked antigorite from a peak shock pressure of 60 GPa intersects the stability fields of several high‐pressure nominally anhydrous minerals (NAMs). On the other hand, the decompression path from peak pressures of 80 to 100 GPa is predicted to remain above the liquidus until ambient pressure is reached. These findings have significant implications for the impact thermal histories of serpentine‐rich hydrous asteroids, such as Ryugu and Bennu.

High entropy alloys (HEAs) are a new class of metals that exhibit unique mechanical performance. Among HEAs, additively manufactured eutectic high entropy alloys (AM-EHEAs) have recently emerged as candidate materials for use in extreme conditions due to their simultaneous high strength and ductility. However, the deformation and structural evolution of AM-EHEAs under conditions of high pressure have not been well characterized, limiting their use in extreme applications. We present dynamic compression experiments and molecular dynamics simulations studying the structural evolution of AM-EHEA AlCoCrFeNi2.1 when compressed to pressures up to 400 GPa. Our in-situ X-ray diffraction measurements capture the appearance of fcc and bcc phases at different pressure conditions, with pure- and mixed-phase regions. Understanding the phase stability and structural evolution of the AM EHEA offers new insights to guide the development of high-performance complex materials for extreme conditions.

Understanding structural phase transitions is crucial for predicting the macroscopic behaviors of materials under shock compression. In this study, we employed in situ x-ray diffraction to investigate the crystal structures of tin along the Hugoniot. Our results demonstrate that the bct-bcc phase boundary shifts to a higher pressure under shock compression compared to static compression. This shift addresses the observed discontinuity in the relationship between shear strength and shock pressure, anchoring the dynamic bct-bcc phase boundary at 34.7 +/- 2.5 GPa. To elucidate the mechanisms behind the shift, we propose a nucleation model that emphasizes the roles of surface free energy and chemical potential difference in determining the energy barrier for nucleation and the kinetics of phase transformation. This straightforward yet generalized model accounts for hysteresis effects during compression and decompression, particularly when the chemical potential differences approach zero. Additionally, it explains how phase boundaries shift under shock compression, considering competition among various phase transformation pathways. These results underscore the critical role of phase transformation kinetics in interpreting the dynamic properties of materials under shock compression, providing insights that go beyond traditional static phase diagrams.

Nanowire arrays—vertically aligned metal wires with a few hundred nanometers in diameter—are promising nano-structured targets for high-energy-density physics and related applications. We have been developing ultrafast, time-resolved measurements on laser-irradiated targets using the x-ray free electron laser at the SACLA facility. Here, we present fabrication of various kinds of nanowire array in order to explore the absorption mechanism with ultrahigh intensity laser irradiation, and their application to the laser-irradiation experiment is performed at the SACLA facility. To fabricate nanowire arrays with control over their spatial and material parameters, we have developed an approach using an anodic aluminum oxide template and electroplating processes. The nanowire array samples were applied for ultrahigh intensity laser experiments, which coupled with x-ray free-electron-laser facility SACLA. We characterized fundamental “static” data on transmittance calibration for x-ray shadowgraph measurements. We also evaluated the effect of a pre-pulse on spatial changes of a nanowire, showing that the shape of the nanowires was maintained up to a few picoseconds after laser irradiation. On the preliminary laser-irradiation experiments, we observed time-resolved, two-dimensional x-ray images and observed the x-ray transmittance change due to the heating process.

The phase transitions in minerals under shock are crucial for understanding meteorite impact history. Recent time-resolved x-ray diffraction (XRD) studies on silica shocked to 65 GPa proposed the formation of different high-pressure phases between fused silica and quartz. Furthermore, the dynamics of silica behavior under higher pressure need to be investigated, particularly during nonequilibrium superheating before melting. This study examines the time-dependent response of coesite, using laser-driven shock coupled with fast XRD and molecular dynamics simulations with our recently developed machine learning interatomic potential. Our results reveal a transient dense supercooled liquid crystallizes into a semi-disordered d-NiAs-type silica, followed by transforming into either seifertite or stishovite, depending on the pressure. Instead of thermodynamically stable quartz, a back-transformation to coesite phase is identified after release. The complicated phase evolution pathways in shocked coesite provide deeper insights into the high-pressure silica phases observed in the meteorite bombardments on the early Moon, Mars, and Earth.

In this study, we aimed to evaluate the shock-induced behavior of calcite (CaCO3), a potential source of CO and/or CO2. To this end, we experimentally investigated the time evolution of calcite during shock compression and decompression processes at shock pressures up to 234 ± 19 GPa using an ultrafast time-resolved X-ray diffraction (XRD) coupled with a laser-driven shock compression system. The XRD analysis of shocked calcite showed that the amorphization occurred in the shock compression stage at pressures above 86 ± 7 GPa, and that the decomposition reaction, i.e., CaCO3 = CaO + CO2, was not observed in the decompression stage within the nanosecond timescale. This observation indicated that in addition to pressure and temperature, the shock duration (reaction time) is also a critical factor affecting shock-induced structural changes, such as amorphization and decomposition. Furthermore, the nanosecond laser shock employed in this study may be applied to enhance understanding regarding the impact phenomena of micrometer to submillimeter sized projectiles. The present results suggest that the shock-induced decomposition of calcite does not occur during micrometeorite impacts.

We present measurements on Fe2O3 amorphization and melt under laser-driven shock compression up to 209(10) GPa via time-resolved x-ray diffraction. At 122(3) GPa, a diffuse signal is observed indicating the presence of a noncrystalline phase. Structure factors have been extracted up to 182(6) GPa showing the presence of two well-defined peaks. A rapid change in the intensity ratio of the two peaks is identified between 145(12) and 151(12) GPa, indicative of a phase change. The noncrystalline diffuse scattering is consistent with shock amorphization of Fe2O3 between 122(3) and 145(12) GPa, followed by an amorphous-to-liquid transition above 151(12) GPa. Upon release, a noncrystalline phase is observed alongside crystalline α−Fe2O3. The extracted structure factor and pair distribution function of this release phase resemble those reported for Fe2O3 melt at ambient pressure. Published by the American Physical Society 2025

Molybdenum(VI) oxide (MoO3) is a promising semiconductor material that can be used in several functional applications. Understanding the structural response of MoO3 under high-pressure and high-temperature conditions is important for designing a material used in device applications. An X-ray free electron laser (XFEL) enables the structural response under extreme conditions to be probed at the nanosecond timescale. We describe laser-driven shock compression experiments on MoO3 using an XFEL to directly observe the structural evolution of MoO3. When a laser-driven shock wave arrives at a pressure of 61 GPa, MoO3 melts immediately and remains in the molten state for a few nanoseconds. Rapid recrystallization to the α-MoO3 phase and a high-pressure phase MoO3-II is also observed on nanosecond timescales during pressure release. Our results provide insights into the kinetic and phase transition under shock compression and represent the advancement toward the understanding structural response of MoO3 under high-pressure, high-temperature conditions, which has not been studied.

Laser-driven dynamic compression experiments of plastic materials have found surprisingly fast formation of nanodiamonds (ND) via X-ray probing. This mechanism is relevant for planetary models, but could also open efficient synthesis routes for tailored NDs. We investigate the release mechanics of compressed NDs by molecular dynamics simulation of the isotropic expansion of finite size diamond from different P-T states. Analysing the structural integrity along different release paths via molecular dynamic simulations, we found substantial disintegration rates upon shock release, increasing with the on-Hugnoiot shock temperature. We also find that recrystallization can occur after the expansion and hence during the release, depending on subsequent cooling mechanisms. Our study suggests higher ND recovery rates from off-Hugoniot states, e.g., via double-shocks, due to faster cooling. Laser-driven shock compression experiments of polyethylene terephthalate (PET) samples with in situ X-ray probing at the simulated conditions found diamond signal that persists up to 11 ns after breakout. In the diffraction pattern, we observed peak shifts, which we attribute to thermal expansion of the NDs and thus a total release of pressure, which indicates the stability of the released NDs.

In their comment (1), Hawreliak et al. claims that our observation of stacking fault formation and transonic dislocation propagation in diamond (2) is not valid as they interpret the observed features as cracks. In this response letter, we describe our rationale for interpreting the observed features as stacking faults. We also address other points raised in their comments, including the clarifications of how the results of Makarov et al. (3) are not in conflict with our study.

Femtosecond high-intensity laser pulses at intensities surpassing 1014 W/cm2 can generate a diverse range of functional surface nanostructures. Achieving precise control over the production of these functional structures necessitates a thorough understanding of the surface morphology dynamics with nanometer-scale spatial resolution and picosecond-scale temporal resolution. In this study, we show that single XFEL pulses can elucidate structural changes on surfaces induced by laser-generated plasmas using grazing-incidence small-angle X-ray scattering (GISAXS). Using aluminium-coated multilayer samples we distinguish between sub-picosecond (ps) surface morphology dynamics and subsequent multi-ps subsurface density dynamics with nanometer-depth sensitivity. The observed subsurface density dynamics serve to validate advanced simulation models representing matter under extreme conditions. Our findings promise to open new avenues for laser material-nanoprocessing and high-energy-density science.

High-intensity, short-pulse lasers are crucial for generating energetic electrons that produce high-energy-density (HED) states in matter, offering potential applications in igniting dense fusion fuels for fast ignition laser fusion. High-density targets heated by these electrons exhibit spatially non-uniform and highly transient conditions, which have been challenging to characterize due to limitations in diagnostics that provide simultaneous high spatial and temporal resolution. Here, we employ an X-ray Free Electron Laser (XFEL) to achieve spatiotemporally resolved measurements at sub-micron and femtosecond scales on a solid-density copper foil heated by laser-driven fast electrons. Our X-ray transmission imaging reveals the formation of a solid-density hot plasma localized to the laser spot size, surrounded by Fermi degenerate, warm dense matter within a picosecond, and the energy relaxation occurring within the hot plasma over tens of picoseconds. These results validate 2D particle-in-cell simulations incorporating atomic processes and provide insights into the energy transfer mechanisms beyond current simulation capabilities. This work significantly advances our understanding of rapid fast electron heating and energy relaxation in solid-density matter, serving as a key stepping stone towards efficient high-density plasma heating and furthering the fields of HED science and inertial fusion energy research using intense, short-pulse lasers.

We demonstrate a significantly simplified experimental approach for investigating liquid metallic hydrogen, which is crucial to understand the internal structure and evolution of giant planets. Plastic samples were shock-compressed and then probed by short pulses of X-rays generated by free electron lasers. By comparison with ab initio simulations, we provide indirect evidence for the creation of elemental hydrogen in shock-compressed plastics at -150 GPa and -5, 000 K and thus in a regime where hydrogen is predicted to be metallic. Being the most common form of condensed matter in our solar system, and ostensibly the simplest of all elements, hydrogen is the model case for many theoretical studies and we provide a new possibility to benchmark models for conditions with extreme pressures and temperatures. Moreover, this approach will also allow to probe the chemical behavior of metallic hydrogen in mixture with other elements, which, besides its importance for planetary physics, may open up promising pathways for the synthesis of new materials.

High-power, short-pulse laser-driven fast electrons can rapidly heat and ionize a high-density target before it hydrodynamically expands. The transport of such electrons within a solid target has been studied using two-dimensional (2D) imaging of electron-induced Kα radiation. However, it is currently limited to no or picosecond scale temporal resolutions. Here, we demonstrate femtosecond time-resolved 2D imaging of fast electron transport in a solid copper foil using the SACLA x-ray free electron laser (XFEL). An unfocused collimated x-ray beam produced transmission images with sub-micron and ∼10 fs resolutions. The XFEL beam, tuned to its photon energy slightly above the Cu K-edge, enabled 2D imaging of transmission changes induced by electron isochoric heating. Time-resolved measurements obtained by varying the time delay between the x-ray probe and the optical laser show that the signature of the electron-heated region expands at ∼25% of the speed of light in a picosecond duration. Time-integrated Cu Kα images support the electron energy and propagation distance observed with the transmission imaging. The x-ray near-edge transmission imaging with a tunable XFEL beam could be broadly applicable for imaging isochorically heated targets by laser-driven relativistic electrons, energetic protons, or an intense x-ray beam.

The motion of line defects (dislocations) has been studied for more than 60 years, but the maximum speed at which they can move is unresolved. Recent models and atomistic simulations predict the existence of a limiting velocity of dislocation motion between the transonic and subsonic ranges at which the self-energy of dislocation diverges, though they do not deny the possibility of the transonic dislocations. We used femtosecond x-ray radiography to track ultrafast dislocation motion in shock-compressed single-crystal diamond. By visualizing stacking faults extending faster than the slowest sound wave speed of diamond, we show the evidence of partial dislocations at their leading edge moving transonically. Understanding the upper limit of dislocation mobility in crystals is essential to accurately model, predict, and control the mechanical properties of materials under extreme conditions.

Understanding the behavior of matter at extreme pressures of the order of a megabar (Mbar) is essential to gain insight into various physical phenomena at macroscales—the formation of planets, young stars, and the cores of super-Earths, and at microscales—damage to ceramic materials and high-pressure plastic transformation and phase transitions in solids. Under dynamic compression of solids up to Mbar pressures, even a solid with high strength exhibits plastic properties, causing the induced shock wave to split in two: an elastic precursor and a plastic shock wave. This phenomenon is described by theoretical models based on indirect measurements of material response. The advent of x-ray free-electron lasers (XFELs) has made it possible to use their ultrashort pulses for direct observations of the propagation of shock waves in solid materials by the method of phase-contrast radiography. However, there is still a lack of comprehensive data for verification of theoretical models of different solids. Here, we present the results of an experiment in which the evolution of the coupled elastic–plastic wave structure in diamond was directly observed and studied with submicrometer spatial resolution, using the unique capabilities of the x-ray free-electron laser (XFEL). The direct measurements allowed, for the first time, the fitting and validation of the 2D failure model for diamond in the range of several Mbar. Our experimental approach opens new possibilities for the direct verification and construction of equations of state of matter in the ultra-high-stress range, which are relevant to solving a variety of problems in high-energy-density physics.

The Hugoniot equation-of-state, Gruneisen parameter, and structure of laser-shocked polyimide were measured. The polyimide Hugoniots were measured in the pressure range 80-600 GPa and found to be consistent with the extrapolation of previously reported data below 60 GPa. The structural measurements of polyimide shock compressed to pressures of 28-163 GPa were performed using the in situ x-ray diffraction technique, and the results show that the melting pressure of polyimide along its Hugoniot is below 32(+/- 3) GPa, indicating that the discontinuous volume change of the polyimide Hugoniot at similar to 26 GPa observed in previous gas-gun experiments denotes the onset of melting. The consistency of the melting pressure between the previous gas-gun results and the present laser experiments suggests that the shock-melting process of polyimide is independent of the duration of the compression, revealing its rapid melting kinetics.