Showing 1–5 of 5 results for author: Ginestet, H

Nanosecond timescale plasticity in shock-compressed polycrystalline MgO: evidence for transition in mechanism above 100 GPa

Authors: A. Chakraborti, H. Ginestet, F. Bertrand, J. Chantel, S. Merkel, M. Harmand, S. Pandolfi, A. Amouretti, M. Andrzejewski, K. Appel, E. Barraud, A. B. Belonoshko, E. Brambrink, K. Buakor, C. Camarda, O. Castelnau, D. M. Cheshire, G. Collins, T. E. Cowan, C. Crépisson, J. Deng, X. Fang, M. Fitzgerald, A. Gleason, F. Hanby , et al. (58 additional authors not shown)

Abstract: The mechanical properties of ceramics under extreme conditions directly impact applications ranging from shielding spacecrafts, designing plasma facing materials in nuclear fusion to understanding the rheology of deep planetary interiors. Here, we use polycrystalline MgO as a model ceramic to understand the high-pressure-temperature mechanical behaviour of such materials under extreme strain rates… ▽ More The mechanical properties of ceramics under extreme conditions directly impact applications ranging from shielding spacecrafts, designing plasma facing materials in nuclear fusion to understanding the rheology of deep planetary interiors. Here, we use polycrystalline MgO as a model ceramic to understand the high-pressure-temperature mechanical behaviour of such materials under extreme strain rates. We use laser-driven shock compression up to 175(15) GPa on the principal Hugoniot along with ultrafast diagnostics at the European X-ray Free Electron Laser to probe the dominant deformation mechanisms with changing P -T conditions. These near-instantaneous time-resolved snapshots, coupled with elasto-viscoplastic self-consistent (EVPSC) simulations, strongly suggest that MgO attains plastic regime in the nanoseconds scale accompanied by a pressure-mediated change in dominant slip system between 95 and 175 GPa. This work provides a new direct window into the deformation dynamics of polycrystalline ceramics under high-velocity impacts. △ Less

Submitted 5 August, 2026; originally announced August 2026.

Volume Collapse Without a Structural Transition in Shock-Compressed FeO

Authors: C. Crépisson, T. Stevens, M. Fitzgerald, C. Camarda, P. G. Heighway, D. Peake, D. McGonegle, A. Descamps, A. Amouretti, D. A. Chin, K. K. Alaa El-Din, S. Azadi, E. Brambrink, K. Buakor, L. Pennacchioni, M. Sieber, A. Coutinho Dutra, J. Hernandez Gordillo, K. Yamamoto, J. -A. Hernandez, R. Torchio, T. Tschentscher, Y. Wang, H. Taylor, J. Pintor , et al. (99 additional authors not shown)

Abstract: We report x-ray diffraction and emission spectroscopy of FeO under laser-driven shock compression between 31-199 GPa. FeO retains the B1 (rocksalt) structure along the Hugoniot to the melt boundary at 191 GPa. While the phase and volume are broadly consistent with results from static compression, we observe an anomalous 7-10% volume collapse around 60 GPa absent in static experiments. We identify… ▽ More We report x-ray diffraction and emission spectroscopy of FeO under laser-driven shock compression between 31-199 GPa. FeO retains the B1 (rocksalt) structure along the Hugoniot to the melt boundary at 191 GPa. While the phase and volume are broadly consistent with results from static compression, we observe an anomalous 7-10% volume collapse around 60 GPa absent in static experiments. We identify this as an isostructural high-spin to low-spin metallic transition in FeO. The low-spin state is directly evidenced by x-ray emission spectroscopy at 180 GPa. △ Less

Submitted 8 April, 2026; originally announced April 2026.

Comments: 10 pages, 3 figures

X-ray thermal diffuse scattering as a texture-robust temperature diagnostic for dynamically compressed solids

Authors: P. G. Heighway, D. J. Peake, T. Stevens, J. S. Wark, B. Albertazzi, S. J. Ali, L. Antonelli, M. R. Armstrong, C. Baehtz, O. B. Ball, S. Banerjee, A. B. Belonoshko, C. A. Bolme, V. Bouffetier, R. Briggs, K. Buakor, T. Butcher, S. Di Dio Cafiso, V. Cerantola, J. Chantel, A. Di Cicco, A. L. Coleman, J. Collier, G. Collins, A. J. Comley , et al. (97 additional authors not shown)

Abstract: We present a model of x-ray thermal diffuse scattering (TDS) from a cubic polycrystal with an arbitrary crystallographic texture, based on the classic approach of Warren. We compare the predictions of our model with femtosecond x-ray diffraction patterns obtained from ambient and dynamically compressed rolled copper foils obtained at the High Energy Density (HED) instrument of the European X-Ray F… ▽ More We present a model of x-ray thermal diffuse scattering (TDS) from a cubic polycrystal with an arbitrary crystallographic texture, based on the classic approach of Warren. We compare the predictions of our model with femtosecond x-ray diffraction patterns obtained from ambient and dynamically compressed rolled copper foils obtained at the High Energy Density (HED) instrument of the European X-Ray Free-Electron Laser (EuXFEL), and find that the texture-aware TDS model yields more accurate results than does the conventional powder model owed to Warren. Nevertheless, we further show that: with sufficient angular detector coverage, the TDS signal is largely unchanged by sample orientation and in all cases strongly resembles the signal from a perfectly random powder; shot-to-shot fluctuations in the TDS signal resulting from grain-sampling statistics are at the percent level, in stark contrast to the fluctuations in the Bragg-peak intensities (which are over an order of magnitude greater); and TDS is largely unchanged even following texture evolution caused by compression-induced plastic deformation. We conclude that TDS is robust against texture variation, making it a flexible temperature diagnostic applicable just as well to off-the-shelf commercial foils as to ideal powders. △ Less

Submitted 6 August, 2025; originally announced August 2025.

Comments: 22 pages, 13 figures in main article; 5 pages, 1 figure in supplementary material

Observation of Body-Centered Cubic Iron above 200 Gigapascals

Authors: Zuzana Konopkova, Eric Edmund, Orianna B Ball, Agnes Dewaele, Helene Ginestet, Rachel J Husband, Nicolas Jaisle, Cornelius Strohm, Madden S Anae, Daniele Antonangeli, Karen Appel, Marzena Baron, Silvia Boccato, Khachiwan Buakor, Julien Chantel, Hyunchae Cynn, Anand P Dwivedi, Lars Ehm, Konstantin Glazyrin, Heinz Graafsma, Egor Koemets, Torsten Laurus, Hauke Marquardt, Bernhard Massani, James D McHardy , et al. (12 additional authors not shown)

Abstract: The crystallographic structure of iron under extreme conditions is a key benchmark for cutting-edge experimental and numerical methods. Moreover, it plays a crucial role in understanding planetary cores, as it significantly influences the interpretation of observational data and, consequently, insights into their internal structure and dynamics. However, even the structure of pure solid iron under… ▽ More The crystallographic structure of iron under extreme conditions is a key benchmark for cutting-edge experimental and numerical methods. Moreover, it plays a crucial role in understanding planetary cores, as it significantly influences the interpretation of observational data and, consequently, insights into their internal structure and dynamics. However, even the structure of pure solid iron under the Earth's core conditions remains uncertain, with the commonly expected hexagonal close-packed structure energetically competitive with various cubic lattices. In this study, iron was compressed in a diamond anvil cell to above 200 GPa, and dynamically probed near the melting point using MHz frequency X-ray pulses from the European X-ray Free Electron Laser. The emergence of an additional diffraction line at high temperatures suggests the formation of an entropically stabilized bcc structure. Rapid heating and cooling cycles captured intermediate phases, offering new insights into iron's phase transformation paths. The appearance of the bcc phase near melting at extreme pressures challenges current understanding of the iron phase diagram under Earth's core conditions. △ Less

Submitted 21 May, 2025; originally announced May 2025.

Femtosecond temperature measurements of laser-shocked copper deduced from the intensity of the x-ray thermal diffuse scattering

Authors: J. S. Wark, D. J. Peake, T. Stevens, P. G. Heighway, Y. Ping, P. Sterne, B. Albertazzi, S. J. Ali, L. Antonelli, M. R. Armstrong, C. Baehtz, O. B. Ball, S. Banerjee, A. B. Belonoshko, C. A. Bolme, V. Bouffetier, R. Briggs, K. Buakor, T. Butcher, S. Di Dio Cafiso, V. Cerantola, J. Chantel, A. Di Cicco, A. L. Coleman, J. Collier , et al. (100 additional authors not shown)

Abstract: We present 50-fs, single-shot measurements of the x-ray thermal diffuse scattering (TDS) from copper foils that have been shocked via nanosecond laser-ablation up to pressures above 135~GPa. We hence deduce the x-ray Debye-Waller (DW) factor, providing a temperature measurement. The targets were laser-shocked with the DiPOLE 100-X laser at the High Energy Density (HED) endstation of the European X… ▽ More We present 50-fs, single-shot measurements of the x-ray thermal diffuse scattering (TDS) from copper foils that have been shocked via nanosecond laser-ablation up to pressures above 135~GPa. We hence deduce the x-ray Debye-Waller (DW) factor, providing a temperature measurement. The targets were laser-shocked with the DiPOLE 100-X laser at the High Energy Density (HED) endstation of the European X-ray Free-Electron Laser (EuXFEL). Single x-ray pulses, with a photon energy of 18 keV, were scattered from the samples and recorded on Varex detectors. Despite the targets being highly textured (as evinced by large variations in the elastic scattering), and with such texture changing upon compression, the absolute intensity of the azimuthally averaged inelastic TDS between the Bragg peaks is largely insensitive to these changes, and, allowing for both Compton scattering and the low-level scattering from a sacrificial ablator layer, provides a reliable measurement of $T/Θ_D^2$, where $Θ_D$ is the Debye temperature. We compare our results with the predictions of the SESAME 3336 and LEOS 290 equations of state for copper, and find good agreement within experimental errors. We thus demonstrate that single-shot temperature measurements of dynamically compressed materials can be made via thermal diffuse scattering of XFEL radation. △ Less

Submitted 6 January, 2025; originally announced January 2025.

Comments: 17 pages, 9 figures in main article; 10 pages, 5 figures in supplementary material