Showing 1–21 of 21 results for author: Nagler, B

Physics-Guided Deep Learning For High Resolution X-ray Imaging

Authors: Shao Xian Lee, Aashwin Ananda Mishra, Ariel Arnott, Meriame Berboucha, Nina Boiadjieva, Gourab Chatterjee, Eric Cunningham, Nick Czapla, Gilliss Dyer, Jonathan Ehni, Robert Ettelbrick, Anna Grassi, Mickael Grech, Philip Hart, Dimitri Khaghani, Hae Ja Lee, Peregrine McGehee, Bob Nagler, Paul Neumayer, Caterina Riconda, Marc Welch, Andrea Zabala, Eric Galtier, Quynh L. Nguyen

Abstract: Imperfections in X-ray imaging systems can limit their performance, especially in High Energy Density (HED) or Inertial Fusion Energy (IFE)-relevant experiments that are typically single shot, by introducing structured, non-stationary features that overlap with the signal of interest. When the X-ray transmission is reconstructed by typical flat-field normalization, even small shot-to-shot drift of… ▽ More Imperfections in X-ray imaging systems can limit their performance, especially in High Energy Density (HED) or Inertial Fusion Energy (IFE)-relevant experiments that are typically single shot, by introducing structured, non-stationary features that overlap with the signal of interest. When the X-ray transmission is reconstructed by typical flat-field normalization, even small shot-to-shot drift of structured features imprints residual patterns onto transmission maps, degrading signal visibility and biasing measurements such as electron density, velocity and feature sizes. We investigate this limitation by modeling the artifacts as a separable feature layer and training a U-Net architecture to estimate and infer them directly from the experimental data. We compare our method against Fourier filtering and more advanced procedures like Dynamic Flat-Field Normalization (DFFN) to evaluate artifact suppression capability and signal preservation in the reconstructed transmission maps. In multiple synthetic injection tests, our Physics-Guided Deep Learning approach is able to obtain an improvement in mean Structural Similarity Index (SSIM) from 0.345 to 0.906 and from 0.0679 to 0.945, while better preserving filament profiles and reducing degradation of the filament signal during artifact suppression. Additionally, we utilize deep ensembles to obtain predictive epistemic uncertainty estimates for the U-Net based reconstruction, to ensure Out Of Distribution (OOD) robustness for this procedure. △ Less

Submitted 2 May, 2026; originally announced May 2026.

XFEL Imaging Techniques for High Energy Density and Inertial Fusion Energy Research at HED-HiBEF

Authors: Alejandro Laso Garcia, Mikhail Mishchenko, Victorien Bouffetier, Gabriel Perez-Callejo, Karen Appel, Alexey Arefiev, Carsten Baehtz, Erik Brambrink, Mihail Cernaianu, Domenico Doria, Tobias Dornheim, Gillis M. Dyer, Nicolas Fefeu, Eric Galtier, Thomas Gawne, Petru V. Ghenuche, Sebastian Goede, Johannes Hagemann, Marie-Luise Herbert, Hauke Höppner, Lingen Huang, Oliver Humphries, Mae Jones, Dimitri Khaghani, Thomas Kluge , et al. (31 additional authors not shown)

Abstract: The imaging platform developed at the High Energy Density - Helmholtz International Beamline for Extreme Fields (HED-HiBEF) instrument at the European XFEL and its applications to high energy density and fusion related research are presented. The platform combines the XFEL beam with the high-intensity short-pulse laser ReLaX and the high-energy nanosecond-pulse laser DiPOLE-100X. The spatial resol… ▽ More The imaging platform developed at the High Energy Density - Helmholtz International Beamline for Extreme Fields (HED-HiBEF) instrument at the European XFEL and its applications to high energy density and fusion related research are presented. The platform combines the XFEL beam with the high-intensity short-pulse laser ReLaX and the high-energy nanosecond-pulse laser DiPOLE-100X. The spatial resolution is better than 500 nm and the temporal resolution of the order of 50 fs. We show examples of blast waves and converging cylindrical shocks in aluminium, resonant absorption measurements of specific charged states in copper with ReLaX and planar shocks in polystyrene material generated by DiPOLE-100X. We also discuss the possibilities introduced by combining this imaging platform with a kJ-class laser. △ Less

Submitted 20 January, 2026; originally announced January 2026.

Comments: 24 pages, 6 figures. Submitted to PPCF Special Issue Featuring the Plenary and Invited Talks from the 51st EPS Conference on Plasma Physics, 7 - 11 July 2025

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

Roadmap for warm dense matter physics

Authors: Jan Vorberger, Frank Graziani, David Riley, Andrew D. Baczewski, Isabelle Baraffe, Mandy Bethkenhagen, Simon Blouin, Maximilian P. Böhme, Michael Bonitz, Michael Bussmann, Alexis Casner, Witold Cayzac, Peter Celliers, Gilles Chabrier, Nicolas Chamel, Dave Chapman, Mohan Chen, Jean Clérouin, Gilbert Collins, Federica Coppari, Tilo Döppner, Tobias Dornheim, Luke B. Fletcher, Dirk O. Gericke, Siegfried Glenzer , et al. (49 additional authors not shown)

Abstract: This roadmap presents the state-of-the-art, current challenges and near future developments anticipated in the thriving field of warm dense matter physics. Originating from strongly coupled plasma physics, high pressure physics and high energy density science, the warm dense matter physics community has recently taken a giant leap forward. This is due to spectacular developments in laser technolog… ▽ More This roadmap presents the state-of-the-art, current challenges and near future developments anticipated in the thriving field of warm dense matter physics. Originating from strongly coupled plasma physics, high pressure physics and high energy density science, the warm dense matter physics community has recently taken a giant leap forward. This is due to spectacular developments in laser technology, diagnostic capabilities, and computer simulation techniques. Only in the last decade has it become possible to perform accurate enough simulations \& experiments to truly verify theoretical results as well as to reliably design experiments based on predictions. Consequently, this roadmap discusses recent developments and contemporary challenges that are faced by theoretical methods, and experimental techniques needed to create and diagnose warm dense matter. A large part of this roadmap is dedicated to specific warm dense matter systems and applications in astrophysics, inertial confinement fusion and novel material synthesis. △ Less

Submitted 13 February, 2026; v1 submitted 5 May, 2025; originally announced May 2025.

Analysis and Mitigation of Crosstalk in a Multi-Parameter Laser Beam Diagnostic System

Authors: Benjamin Nagler

Abstract: Accurate characterization of laser beams is crucial for applications ranging from laser-based material processing to gravitational wave detection, where even minor measurement deviations can significantly impact system performance. This work investigates crosstalk effects in a multi-parameter laser beam diagnostic system designed to simultaneously measure six beam parameters: pointing angles, cent… ▽ More Accurate characterization of laser beams is crucial for applications ranging from laser-based material processing to gravitational wave detection, where even minor measurement deviations can significantly impact system performance. This work investigates crosstalk effects in a multi-parameter laser beam diagnostic system designed to simultaneously measure six beam parameters: pointing angles, centroid positions, wavefront curvature, and beam diameter. Using sequential ray-optical simulations in Zemax, a comprehensive analysis of parameter interdependencies is performed through a systematic parameter sweep across 15625 unique combinations within specified measurement ranges. The results reveal significant crosstalk effects between several parameters, which are traced back to specific optical components in the system. To address these issues and improve accuracy, a mathematical framework for crosstalk mitigation based on Taylor series expansions is developed. The mitigation method reduces measurement deviations significantly by up to one order of magnitude. This work provides insights into the origins and mitigation of crosstalk effects in optical measurement systems, particularly relevant for high-accuracy applications. △ Less

Submitted 30 April, 2025; originally announced April 2025.

Comments: 18 pages, 7 figures

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

X-ray Microscopy and Talbot Imaging with the Matter in Extreme Conditions X-ray Imager at LCLS

Authors: Eric Galtier, Hae Ja Lee, Dimitri Khaghani, Nina Boiadjieva, Peregrine McGehee, Ariel Arnott, Brice Arnold, Meriame Berboucha, Eric Cunningham, Nick Czapla, Gilliss Dyer, Bob Ettelbrick, Philip Hart, Philip Heimann, Marc Welch, Mikako Makita, Arianna E. Gleason, Silvia Pandolfi, Anne Sakdinawat, Yanwei Liu, Michael J. Wojcik, Daniel Hodge, Richard Sandberg, Maria Pia Valdivia, Victorien Bouffetier , et al. (3 additional authors not shown)

Abstract: The last decade has shown the great potential that X-ray Free Electron Lasers (FEL) have to study High Energy Density (HED) physics. Experiments at FELs have made significant breakthroughs in Shock Physics and Dynamic Diffraction, Dense Plasma Physics and Warm Dense Matter Science, using techniques such as isochoric heating, inelastic scattering, small angle scattering and X-ray diffraction. In ad… ▽ More The last decade has shown the great potential that X-ray Free Electron Lasers (FEL) have to study High Energy Density (HED) physics. Experiments at FELs have made significant breakthroughs in Shock Physics and Dynamic Diffraction, Dense Plasma Physics and Warm Dense Matter Science, using techniques such as isochoric heating, inelastic scattering, small angle scattering and X-ray diffraction. In addition, and complementary to these techniques, the coherent properties of the FEL beam can be used to image HED samples with high fidelity. We present new imaging diagnostics and techniques developed at the Matter in Extreme Conditions (MEC) instrument at Linac Coherent Light Source (LCLS) over the last few years. We show results in Phase Contrast Imaging geometry, where the X-ray beam propagates from the target to a camera revealing its phase, as well as in Direct Imaging geometry, where a real image of the sample plane is produced in the camera with a spatial resolution down to 200 nm. Last, we show an implementation of the Talbot Imaging method allowing both X-ray phase and intensity measurements change introduced by a target with sub-micron resolution. △ Less

Submitted 15 February, 2025; v1 submitted 28 February, 2024; originally announced May 2024.

Radiation and Heat Transport in Divergent Shock-Bubble Interactions

Authors: Kelin Kurzer-Ogul, Brian M. Haines, David S. Montgomery, Silvia Pandolfi, Joshua P. Sauppe, Andrew F. T. Leong, Daniel Hodge, Pawel M. Kozlowski, Stefano Marchesini, Eric Cunningham, Eric Galtier, Dimitri Khaghani, Hae Ja Lee, Bob Nagler, Richard L. Sandberg, Arianna E. Gleason, Hussein Aluie, Jessica K. Shang

Abstract: Shock-bubble interactions (SBI) are important across a wide range of physical systems. In inertial confinement fusion, interactions between laser-driven shocks and micro-voids in both ablators and foam targets generate instabilities that are a major obstacle in achieving ignition. Experiments imaging the collapse of such voids at high energy densities (HED) are constrained by spatial and temporal… ▽ More Shock-bubble interactions (SBI) are important across a wide range of physical systems. In inertial confinement fusion, interactions between laser-driven shocks and micro-voids in both ablators and foam targets generate instabilities that are a major obstacle in achieving ignition. Experiments imaging the collapse of such voids at high energy densities (HED) are constrained by spatial and temporal resolution, making simulations a vital tool in understanding these systems. In this study, we benchmark several radiation and thermal transport models in the xRAGE hydrodynamic code against experimental images of a collapsing mesoscale void during the passage of a 300 GPa shock. We also quantitatively examine the role of transport physics in the evolution of the SBI. This allows us to understand the dynamics of the interaction at timescales shorter than experimental imaging framerates. We find that all radiation models examined reproduce empirical shock velocities within experimental error. Radiation transport is found to reduce shock pressures by providing an additional energy pathway in the ablation region, but this effect is small ($\sim$1\% of total shock pressure). Employing a flux-limited Spitzer model for heat conduction, we find that flux limiters between 0.03 and 0.10 produce agreement with experimental velocities, suggesting that the system is well-within the Spitzer regime. Higher heat conduction is found to lower temperatures in the ablated plasma and to prevent secondary shocks at the ablation front, resulting in weaker primary shocks. Finally, we confirm that the SBI-driven instabilities observed in the HED regime are baroclinically driven, as in the low energy case. △ Less

Submitted 5 March, 2024; originally announced March 2024.

Comments: 14 pages, 12 figures

Report number: LA-UR-23-31881

Speed of sound in methane under conditions of planetary interiors

Authors: Thomas G. White, Hannah Poole, Emma E. McBride, Matthew Oliver, Adrien Descamps, Luke B. Fletcher, W. Alex Angermeier, Cameron H. Allen, Karen Appel, Florian P. Condamine, Chandra B. Curry, Francesco Dallari, Stefan Funk, Eric Galtier, Eliseo J. Gamboa, Maxence Gauthier, Peter Graham, Sebastian Goede, Daniel Haden, Jongjin B. Kim, Hae Ja Lee, Benjamin K. Ofori-Okai, Scott Richardson, Alex Rigby, Christopher Schoenwaelder , et al. (10 additional authors not shown)

Abstract: We present direct observations of acoustic waves in warm dense matter. We analyze wave-number- and energy-resolved x-ray spectra taken from warm dense methane created by laser heating a cryogenic liquid jet. X-ray diffraction and inelastic free-electron scattering yield sample conditions of 0.3$\pm$0.1 eV and 0.8$\pm$0.1 g/cm$^3$, corresponding to a pressure of $\sim$13 GPa. Inelastic x-ray scatte… ▽ More We present direct observations of acoustic waves in warm dense matter. We analyze wave-number- and energy-resolved x-ray spectra taken from warm dense methane created by laser heating a cryogenic liquid jet. X-ray diffraction and inelastic free-electron scattering yield sample conditions of 0.3$\pm$0.1 eV and 0.8$\pm$0.1 g/cm$^3$, corresponding to a pressure of $\sim$13 GPa. Inelastic x-ray scattering was used to observe the collective oscillations of the ions. With a highly improved energy resolution of $\sim$50 meV, we could clearly distinguish the Brillouin peaks from the quasielastic Rayleigh feature. Data at different wave numbers were utilized to derive a sound speed of 5.9$\pm$0.5 km/s, marking a high-temperature data point for methane and demonstrating consistency with Birch's law in this parameter regime. △ Less

Submitted 3 May, 2024; v1 submitted 13 November, 2023; originally announced November 2023.

Comments: 7 pages, 4 figures

Journal ref: Physical Review Research 6 (2024) L022029

Characterizing quantum gases in time-controlled disorder realizations using cross-correlations of density distributions

Authors: Silvia Hiebel, Benjamin Nagler, Sian Barbosa, Jennifer Koch, Artur Widera

Abstract: The role of disorder on physical systems has been widely studied in the macroscopic and microscopic world. While static disorder is well understood in many cases, the impact of time-dependent disorder on quantum gases is still poorly investigated. In our experimental setup, we introduce and characterize a method capable of producing time-controlled optical-speckle disorder. Experimentally, coheren… ▽ More The role of disorder on physical systems has been widely studied in the macroscopic and microscopic world. While static disorder is well understood in many cases, the impact of time-dependent disorder on quantum gases is still poorly investigated. In our experimental setup, we introduce and characterize a method capable of producing time-controlled optical-speckle disorder. Experimentally, coherent light illuminates a combination of a static and a rotating diffuser, thereby collecting a spatially varying phase due to the diffusers' structure and a temporally variable phase due to the relative rotation. Controlling the rotation of the diffuser allows changing the speckle realization or, for future work, the characteristic time scale of the change of the speckle pattern, i.e. the correlation time, matching typical time scales of the quantum gases investigated. We characterize the speckle pattern ex-situ by measuring its intensity distribution cross-correlating different intensity patterns. In-situ, we observe its impact on a molecular Bose-Einstein condensate (BEC) and cross-correlate the density distributions of BECs probed in different speckle realizations. As one diffuser rotates relative to the other around the common optical axis, we trace the optical speckle's intensity cross-correlations and the quantum gas' density cross-correlations. Our results show comparable outcomes for both measurement methods. The setup allows us to tune the disorder potential adapted to the characteristics of the quantum gas. These studies pave the way for investigating nonequilibrium physics in interacting quantum gases using controlled dynamical-disorder potentials. △ Less

Submitted 25 January, 2024; v1 submitted 28 June, 2023; originally announced June 2023.

Comments: 23 pages, 8 figures

Journal ref: New J. Phys. 26 013042 (2024)

Investigating Mechanisms of State Localization in Highly-Ionized Dense Plasmas

Authors: Thomas Gawne, Thomas Campbell, Alessandro Forte, Patrick Hollebon, Gabriel Perez-Callejo, Oliver Humphries, Oliver Karnbach, Muhammad F. Kasim, Thomas R. Preston, Hae Ja Lee, Alan Miscampbell, Quincy Y. van den Berg, Bob Nagler, Shenyuan Ren, Ryan B. Royle, Justin S. Wark, Sam M. Vinko

Abstract: We present the first experimental observation of K$_β$ emission from highly charged Mg ions at solid density, driven by intense x-rays from a free electron laser. The presence of K$_β$ emission indicates the $n=3$ atomic shell is relocalized for high charge states, providing an upper constraint on the depression of the ionization potential. We explore the process of state relocalization in dense p… ▽ More We present the first experimental observation of K$_β$ emission from highly charged Mg ions at solid density, driven by intense x-rays from a free electron laser. The presence of K$_β$ emission indicates the $n=3$ atomic shell is relocalized for high charge states, providing an upper constraint on the depression of the ionization potential. We explore the process of state relocalization in dense plasmas from first principles using finite-temperature density functional theory alongside a wavefunction localization metric, and find excellent agreement with experimental results. △ Less

Submitted 14 August, 2023; v1 submitted 8 February, 2023; originally announced February 2023.

Comments: 22 pages, 13 figures

Development of slurry targets for high repetition-rate XFEL experiments

Authors: Raymond F. Smith, Vinay Rastogi, Amy E. Lazicki, Martin G. Gorman, Richard Briggs, Amy L. Coleman, Carol Davis, Saransh Singh, David McGonegle, Samantha M. Clarke, Travis Volz, Trevor Hutchinson, Christopher McGuire, Dayne E. Fratanduono, Damian C. Swift, Eric Folsom, Cynthia A. Bolme, Arianna E. Gleason, Federica Coppari, Hae Ja Lee, Bob Nagler, Eric Cunningham, Eduardo Granados, Phil Heimann, Richard G. Kraus , et al. (4 additional authors not shown)

Abstract: Combining an x-ray free electron laser (XFEL) with high power laser drivers enables the study of phase transitions, equation-of-state, grain growth, strength, and transformation pathways as a function of pressure to 100s GPa along different thermodynamic compression paths. Future high-repetition rate laser operation will enable data to be accumulated at >1 Hz which poses a number of experimental c… ▽ More Combining an x-ray free electron laser (XFEL) with high power laser drivers enables the study of phase transitions, equation-of-state, grain growth, strength, and transformation pathways as a function of pressure to 100s GPa along different thermodynamic compression paths. Future high-repetition rate laser operation will enable data to be accumulated at >1 Hz which poses a number of experimental challenges including the need to rapidly replenish the target. Here, we present a combined shock-compression and X-ray diffraction study on vol% epoxy(50)-crystalline grains(50) (slurry) targets, which can be fashioned into extruded ribbons for high repetition-rate operation. For shock-loaded NaCl-slurry samples, we observe pressure, density and temperature states within the embedded NaCl grains consistent with observations for shock-compressed single-crystal NaCl. △ Less

Submitted 11 January, 2022; originally announced January 2022.

Comments: 12 pages, 9 figures

Probing ultrafast laser plasma processes inside solids with resonant small-angle X-ray scattering

Authors: Lennart Gaus, Lothar Bischoff, Michael Bussmann, Eric Cunningham, Chandra B. Curry, Eric Galtier, Maxence Gauthier, Alejandro Laso García, Marco Garten, Siegfried Glenzer, Jörg Grenzer, Christian Gutt, Nicholas J. Hartley, Lingen Huang, Uwe Hübner, Dominik Kraus, Hae Ja Lee, Emma E. McBride, Josefine Metzkes-Ng, Bob Nagler, Motoaki Nakatsutsumi, Jan Nikl, Masato Ota, Alexander Pelka, Irene Prencipe , et al. (11 additional authors not shown)

Abstract: Extreme states of matter exist throughout the universe e.g. inside planetary cores, stars or astrophysical jets. Such conditions are generated in the laboratory in the interaction of powerful lasers with solids, and their evolution can be probed with femtosecond precision using ultra-short X-ray pulses to study laboratory astrophysics, laser-fusion research or compact particle acceleration. X-ray… ▽ More Extreme states of matter exist throughout the universe e.g. inside planetary cores, stars or astrophysical jets. Such conditions are generated in the laboratory in the interaction of powerful lasers with solids, and their evolution can be probed with femtosecond precision using ultra-short X-ray pulses to study laboratory astrophysics, laser-fusion research or compact particle acceleration. X-ray scattering (SAXS) patterns and their asymmetries occurring at X-ray energies of atomic bound-bound transitions contain information on the volumetric nanoscopic distribution of density, ionization and temperature. Buried heavy ion structures in high intensity laser irradiated solids expand on the nanometer scale following heat diffusion, and are heated to more than 2 million Kelvin. These experiments demonstrate resonant SAXS with the aim to better characterize dynamic processes in extreme laboratory plasmas. △ Less

Submitted 14 December, 2020; originally announced December 2020.

Mapping the Electronic Structure of Warm Dense Nickel via Resonant Inelastic X-ray Scattering

Authors: O. S. Humphries, R. S. Marjoribanks, Q. van den Berg, E. C. Galtier, M. F. Kasim, H. J. Lee, A. J. F. Miscampbell, B. Nagler, R. Royle, J. S. Wark, S. M. Vinko

Abstract: The development of high-brightness free-electron lasers (FEL) has revolutionised our ability to create and study matter in the high-energy-density (HED) regime. Current diagnostic techniques have been very successful in yielding information on fundamental thermodynamic plasma properties, but provide only limited or indirect information on the detailed quantum structure of these systems, and on how… ▽ More The development of high-brightness free-electron lasers (FEL) has revolutionised our ability to create and study matter in the high-energy-density (HED) regime. Current diagnostic techniques have been very successful in yielding information on fundamental thermodynamic plasma properties, but provide only limited or indirect information on the detailed quantum structure of these systems, and on how it is affected by ionization dynamics. Here we show how the electronic structure of solid-density nickel, heated to temperatures of 10's of eV on femtosecond timescales, can be studied by resonant (Raman) inelastic x-ray scattering (RIXS) using the Linac Coherent Light Source FEL. We present single-shot measurements of the valence density of states in the x-ray-heated transient system, and extract simultaneously electron temperatures, ionization, and ionization potential energies. The RIXS spectrum provides a wealth of information on the valence structure of the HED system that goes beyond what can be extracted from x-ray absorption or emission spectroscopy alone. △ Less

Submitted 26 October, 2020; v1 submitted 16 January, 2020; originally announced January 2020.

Journal ref: Phys. Rev. Lett. 125, 195001 (2020)

Impact of free electron degeneracy on collisional rates in plasmas

Authors: Gareth O. Williams, H. -K. Chung, S. Künzel, V. Hilbert, U. Zastrau, H. Scott, S. Daboussi, B. Iwan, A. I. Gonzalez, W. Boutu, H. J. Lee, B. Nagler, E. Granados, E. Galtier, P. Heimann, B. Barbrel, R. W. Lee, B. I. Cho, P. Renaudin, H. Merdji, Ph. Zeitoun, M. Fajardo

Abstract: Degenerate plasmas, in which quantum effects dictate the behavior of free electrons, are ubiquitous on earth and throughout space. Transitions between bound and free electron states determine basic plasma properties, yet the effects of degeneracy on these transitions have only been theorized. Here, we use an x-ray free electron laser to create and characterize a degenerate plasma. We observe a cor… ▽ More Degenerate plasmas, in which quantum effects dictate the behavior of free electrons, are ubiquitous on earth and throughout space. Transitions between bound and free electron states determine basic plasma properties, yet the effects of degeneracy on these transitions have only been theorized. Here, we use an x-ray free electron laser to create and characterize a degenerate plasma. We observe a core electron fluorescence spectrum that cannot be reproduced by models that ignore free electron degeneracy.We show that degeneracy acts to restrict the available electron energy states, thereby slowing the rate of transitions to and from the continuum. We couple degeneracy and bound electron dynamics in an existing collisional-radiative code, which agrees well with observations. The impact of the shape of the cross section, and hence the magnitude of the correction due to degeneracy, is also discussed. This study shows that degeneracy in plasmas can significantly influence experimental observables such as the emission spectra, and that these effects can be included parametrically in well-established atomic physics codes. This work narrows the gap in understanding between the condensed-matter and plasma phases, which coexist in myriad scenarios. △ Less

Submitted 6 January, 2020; v1 submitted 19 February, 2019; originally announced February 2019.

Journal ref: Phys. Rev. Research 1, 033216 (2019)

Melting and phase change for laser-shocked iron

Authors: S. White, B. Kettle, C. L. S. Lewis, D. Riley, J. Vorberger, S. H. Glenzer, E. Gamboa, B. Nagler, F. Tavella, H. J. Lee, C. D. Murphy, D. O. Gericke

Abstract: Using the LCLS facility at the SLAC National Accelerator Laboratory, we have observed X-ray scattering from iron compressed with laser driven shocks to Earth-core like pressures above 400GPa. The data shows shots where melting is incomplete and we observe hexagonal close packed (hcp) crystal structure at shock compressed densities up to 14.0 gcm-3 but no evidence of a double-hexagonal close packed… ▽ More Using the LCLS facility at the SLAC National Accelerator Laboratory, we have observed X-ray scattering from iron compressed with laser driven shocks to Earth-core like pressures above 400GPa. The data shows shots where melting is incomplete and we observe hexagonal close packed (hcp) crystal structure at shock compressed densities up to 14.0 gcm-3 but no evidence of a double-hexagonal close packed (dhcp) crystal. The observation of a crystalline structure at these densities, where shock heating is expected to be in excess of the equilibrium melt temperature, may indicate superheating of the solid. These results are important for equation of state modelling at high strain rates relevant for impact scenarios and laser-driven shock wave experiments. △ Less

Submitted 23 November, 2018; originally announced November 2018.

Journal ref: Phys. Rev. Research 2, 033366 (2020)

Setup for meV-resolution inelastic X-ray scattering measurements at the Matter in Extreme Conditions Endstation at the LCLS

Authors: E. E. McBride, T. G. White, A. Descamps, L. B. Fletcher, K. Appel, F. Condamine, C. B. Curry, F. Dallari, S. Funk, E. Galtier, M. Gauthier, S. Goede, J. B. Kim, H. J. Lee, B. K. Ofori-Okai, M. Oliver, A. Rigby, C. Schoenwaelder, P. Sun, Th. Tschentscher, B. B. L. Witte, U. Zastrau, G. Gregori, B. Nagler, J. Hastings , et al. (2 additional authors not shown)

Abstract: We describe a setup for performing inelastic X-ray scattering measurements at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source (LCLS). This technique is capable of performing high-, meV-resolution measurements of dynamic ion features in both crystalline and non-crystalline materials. A four-bounce silicon (533) monochromator was used in conjunction with three si… ▽ More We describe a setup for performing inelastic X-ray scattering measurements at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source (LCLS). This technique is capable of performing high-, meV-resolution measurements of dynamic ion features in both crystalline and non-crystalline materials. A four-bounce silicon (533) monochromator was used in conjunction with three silicon (533) diced crystal analyzers to provide an energy resolution of ~50 meV over a range of ~500 meV in single shot measurements. In addition to the instrument resolution function, we demonstrate the measurement of longitudinal acoustic phonon modes in polycrystalline diamond. Furthermore, this setup may be combined with the high intensity laser drivers available at MEC to create warm dense matter, and subsequently measure ion acoustic modes. △ Less

Submitted 5 June, 2018; originally announced June 2018.

Comments: Proceedings for High Temperature Plasma Diagnostics

The Phase-Contrast Imaging Instrument at the Matter in Extreme Conditions Endstation at LCLS

Authors: Bob Nagler, Andreas Schropp, Eric C. Galtier, Brice Arnold, Shaughnessy B. Brown, Alan Fry, Arianna Gleason, Eduardo Granados, Akel Hashim, Jerome B. Hastings, Dirk Samberg, Frank Seiboth, Franz Tavella, Zhou Xing, Hae Ja Lee, Christian G. Schroer

Abstract: We describe the Phase-Contrast Imaging instrument at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source. The instrument can image phenomena with a spatial resolution of a few hundreds of nanometers and at the same time reveal the atomic structure through X-ray diffraction, with a temporal resolution better than 100 femtosecond. It was specifically designed for stu… ▽ More We describe the Phase-Contrast Imaging instrument at the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source. The instrument can image phenomena with a spatial resolution of a few hundreds of nanometers and at the same time reveal the atomic structure through X-ray diffraction, with a temporal resolution better than 100 femtosecond. It was specifically designed for studies relevant to High-Energy-Density Science and can monitor, e.g., shock fronts, phase transitions, or void collapses. This versatile instrument was commissioned last year and is now available to the MEC user community. △ Less

Submitted 26 October, 2016; originally announced October 2016.

Journal ref: Rev. Sci. Instrum. 87, 103701 (2016)

Melting of iron close to Earth's inner core boundary conditions and beyond

Authors: M. Harmand, A. Ravasio, S. Mazevet, J. Bouchet, A. Denoeud, F. Dorchies, Y. Feng, C. Fourment, E . Galtier, J. Gaudin, F. Guyot, R. Kodama, M. Koenig, H. J. Lee, K. Miyanishi, G. Morard, R. Musella, B. Nagler, M. Nakatsutsumi, N. Ozaki, V. Recoules, S. Toleikis, T. Vinci, U. Zastrau, D. Zhu , et al. (1 additional authors not shown)

Abstract: Several important geophysical features such as heat flux at the Core-Mantle Boundary or geodynamo production are intimately related with the temperature profile in the Earth's core. However, measuring the melting curve of iron at conditions corresponding to the Earth inner core boundary under pressure of 330 GPa has eluded scientists for several decades. Significant discrepancies in previously rep… ▽ More Several important geophysical features such as heat flux at the Core-Mantle Boundary or geodynamo production are intimately related with the temperature profile in the Earth's core. However, measuring the melting curve of iron at conditions corresponding to the Earth inner core boundary under pressure of 330 GPa has eluded scientists for several decades. Significant discrepancies in previously reported iron melting temperatures at high pressure have called into question the validity of dynamic measurements. We report measurements made with a novel approach using X-ray absorption spectroscopy using an X-ray free electron laser source coupled to a laser shock experiment. We determine the state of iron along the shock Hugoniot up to 420 GPa (+/- 50) and 10800 K (+/- 1390) and find an upper boundary for the melting curve of iron by detecting solid iron at 130 GPa and molten at 260, 380 and 420 GPa along the shock Hugoniot. Our result establishes unambiguous agreement between dynamic measurement and recent extrapolations from static data thus resolving the long-standing controversy over the reliability of using dynamic compression to study the melting of iron at conditions close to the Earth's inner core boundary and beyond. △ Less

Submitted 7 November, 2014; originally announced November 2014.

Comments: 9 pages 3 figures

Bent crystal spectrometer for both frequency and wavenumber resolved x-ray scattering at a seeded free-electron laser

Authors: Ulf Zastrau, Luke B. Fletcher, Eckhart Foerster, Eric Ch. Galtier, Eliseo Gamboa, Siegfried H. Glenzer, Philipp Heimann, Heike Marschner, Bob Nagler, Andreas Schropp, Ortrud Wehrhan, Hae Ja Lee

Abstract: We present a cylindrically curved GaAs x-ray spectrometer with energy resolution $ΔE/E = 1.1\cdot 10^{-4}$ and wave-number resolution of $Δk/k = 3\cdot 10^{-3}$, allowing plasmon scattering at the resolution limits of the Linac Coherent Light Source (LCLS) x-ray free-electron laser. It spans scattering wavenumbers of 3.6 to $5.2/$Å in 100 separate bins, with only 0.34\% wavenumber blurring. The di… ▽ More We present a cylindrically curved GaAs x-ray spectrometer with energy resolution $ΔE/E = 1.1\cdot 10^{-4}$ and wave-number resolution of $Δk/k = 3\cdot 10^{-3}$, allowing plasmon scattering at the resolution limits of the Linac Coherent Light Source (LCLS) x-ray free-electron laser. It spans scattering wavenumbers of 3.6 to $5.2/$Å in 100 separate bins, with only 0.34\% wavenumber blurring. The dispersion of 0.418~eV/$13.5\,μ$m agrees with predictions within 1.3\%. The reflection homogeneity over the entire wavenumber range was measured and used to normalize the amplitude of scattering spectra. The proposed spectrometer is superior to a mosaic HAPG spectrometer when the energy resolution needs to be comparable to the LCLS seeded bandwidth of 1~eV and a significant range of wavenumbers must be covered in one exposure. △ Less

Submitted 28 July, 2014; originally announced July 2014.

XUV Opacity of Aluminum between the Cold-Solid to Warm-Plasma Transition

Authors: S. M. Vinko, G. Gregori, B. Nagler, T. J. Whitcher, M. P. Desjarlais, R. W. Lee, P. Audebert, J. S. Wark

Abstract: We present calculations of the free-free XUV opacity of warm, solid-density aluminum at photon energies between the plasma frequency at 15 eV and the L-edge at 73 eV, using both density functional theory combined with molecular dynamics and a semi-analytical model in the RPA framework with the inclusion of local field corrections. As the temperature is increased from room temperature to 10 eV, w… ▽ More We present calculations of the free-free XUV opacity of warm, solid-density aluminum at photon energies between the plasma frequency at 15 eV and the L-edge at 73 eV, using both density functional theory combined with molecular dynamics and a semi-analytical model in the RPA framework with the inclusion of local field corrections. As the temperature is increased from room temperature to 10 eV, with the ion and electron temperatures equal, we calculate an increase in the opacity in the range over which the degree of ionization is constant. The effect is less pronounced if only the electron temperature is allowed to increase. The physical significance of these increases is discussed in terms of intense XUV-laser matter interactions on both femtosecond and picosecond time-scales. △ Less

Submitted 1 April, 2009; originally announced April 2009.

Comments: 4 pages, 3 figures