arXiv subjects

Siegfried Glenzer

Publications and source records attributed to Siegfried Glenzer.

15 recordsLinked to original sources

arXiv2026

Miscibility and Transport Properties in Hydrogen-Neon Mixtures

The mixing behavior of hydrogen with heavier elements plays a key role in modeling the interiors of giant planets such as Jupiter and Saturn. Using density functional theory combined with molecular dynamics, we investigate hydrogen-neon mixtures and find that the minimum pressure required to trigger phase separation is substantially lower than in hydrogen-helium mixtures. Our simulations further reveal that the presence of neon stabilizes hydrogen molecules even at temperatures of 10000 K and pressures of 10 Mbar, similar to trends observed in hydrogen-helium mixtures but significantly more pronounced. This stabilization is accompanied by a reduction of several orders of magnitude in the electrical conductivity compared to pure hydrogen. These results, together with the larger X-ray scattering cross section of neon, establish hydrogen-neon as a valuable experimental surrogate for probing phase separation in hydrogen-rich mixtures and provide new insight into the physical mechanisms in hydrogen and mixtures with heavier elements under planetary interior conditions

astro-ph.EP↗

arXiv2026

Roadmap for warm dense matter physics

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.

physics.plasm-ph↗

arXiv2026

Correlation function metrology for warm dense matter: Recent developments and practical guidelines

X-ray Thomson scattering (XRTS) has emerged as a valuable diagnostic for matter under extreme conditions, as it captures the intricate many-body physics of the probed sample. Recent advances, such as the model-free temperature diagnostic of Dornheim et al. [Nat.Commun. 13, 7911 (2022)], have demonstrated how much information can be extracted directly within the imaginary-time formalism. However, since the imaginary-time formalism is a concept often difficult to grasp, we provide here a systematic overview of its theoretical foundations and explicitly demonstrate its practical applications to temperature inference, including relevant subtleties. Furthermore, we present recent developments that enable the determination of the absolute normalization, Rayleigh weight, and density from XRTS measurements without reliance on uncontrolled model assumptions. Finally, we outline a unified workflow that guides the extraction of these key observables, offering a practical framework for applying the method to interpret experimental measurements.

physics.plasm-ph↗

arXiv2024

Characterization of foam-filled hohlraums for inertial fusion experiments

On the path towards high-gain inertial confinement fusion ignition, foams are being considered to tamp the hohlraum wall-motion, and mitigate laser backscattering from Stimulated Raman Scattering (SRS) and Stimulated Brillouin Scattering (SBS). Here we present the results from an experimental campaign on foam-filled hohlraums conducted at the OMEGA laser facility. SiO2 foam-fills, with densities as low as 1 mg/cm3, successfully reduce the gold wall expansion, with laser backscattering comparable to gas-fill.

physics.plasm-ph↗

arXiv2023

Probing the dynamics of solid density micro-wire targets after ultra-intense laser irradiation using a free-electron laser

In this paper, we present an experiment that explores the plasma dynamics of a 7 micron diameter carbon wire after being irradiated with a near-relativistic-intensity short pulse laser. Using an X-ray Free Electron Laser pulse to measure the small angle X-ray scattering signal, we observe that the scattering surface is bent and prone to instability over tens of picoseconds. The dynamics of this process are consistent with the presence of a sharp, propagating shock front inside the wire, moving at a speed close to the hole boring velocity.

physics.plasm-ph↗

arXiv2022

Ambient temperature pressure driven alkane dehydrogenation by palladium metal

Dehydrogenation of alkanes is of increasing importance in fulfilling global demand for olefins and offers a potential source of carbon-neutral hydrogen as a co-product. Currently commercial dehydrogenation processes occur at high-temperatures (500-900$^\circ$C) which is energy intensive and results in side reactions and rapid coking of the catalysts. In addition the hydrogen produced is often burned to maintain temperature and to inhibit the back reaction. Here we demonstrate pressure as a parameter to enable novel chemical catalytic processes and demonstrate ambient-temperature dehydrogenation of alkanes by palladium at 50-100 MPa pressures, with both hydrogen gas and olefins recovered on decompression. This reaction follows a fundamentally different path to current commercial high-temperature low-pressure dehydrogenation processes with the palladium catalyst reversibly forming a hydride intermediate.

cond-mat.mtrl-sci↗

arXiv2022

Shock Hugoniot of diamond from 3 to 80 TPa

The principal Hugoniot of carbon, initially diamond, was measured from 3 to 80 TPa (30 to 800 million atmospheres), the highest pressure ever achieved, using radiography of spherically-converging shocks. The shocks were generated by ablation of a plastic coating by soft x-rays in a laser-heated hohlraum at the National Ignition Facility (NIF). Experiments were performed with low and high drive powers, spanning different but overlapping pressure ranges. The radius-time history of the shock, and the profile of mass density behind, were determined by profile-matching from a time-resolved x-ray radiograph across the diameter of the sphere. Above ~50 TPa, the heating induced by the shock was great enough to ionize a significant fraction of K-shell electrons, reducing the opacity to the 10.2 keV probe x-rays. The opacity and mass density were deduced simultaneously using the constraint that the total mass of the sample was constant. The Hugoniot and opacity were consistent with density functional theory calculations of the electronic states and equation of state (EOS), and varied significantly from theoretical Hugoniots based on Thomas-Fermi theory. Theoretical models used to predict the compressibility of diamond ablator experiments at the NIF, producing the highest neutron yields so far from inertial confinement fusion experiments, are qualitatively consistent with our EOS measurements but appear to overpredict the compressibility slightly. These measurements help to evaluate theoretical techniques and constrain wide-range EOS models applicable to white dwarf stars, which are the ultimate evolutionary form of at least 97% of stars in the galaxy.

physics.plasm-ph↗

arXiv2022

Magnetic field amplification by a plasma cavitation instability in relativistic shock precursors

Plasma streaming instabilities play an important role in magnetic field amplification and particle acceleration in relativistic shocks and their environments. However, in the far shock precursor region where accelerated particles constitute a highly relativistic and dilute beam, streaming instabilities typically become inefficient and operate at very small scales when compared to the gyroradii of the beam particles. We report on a plasma cavitation instability that is driven by dilute relativistic beams and can increase both the magnetic field strength and coherence scale by orders of magnitude to reach near-equipartition values with the beam energy density. This instability grows after the development of the Weibel instability and is associated with the asymmetric response of background leptons and ions to the beam current. The resulting net inductive electric field drives a strong energy asymmetry between positively and negatively charged beam species. Large-scale particle-in-cell simulations are used to verify analytical predictions for the growth and saturation level of the instability and indicate that it is robust over a wide range of conditions, including those associated with pair-loaded plasmas. These results can have important implications for the magnetization and structure of shocks in gamma-ray bursts, and more generally for magnetic field amplification and asymmetric scattering of relativistic charged particles in plasma astrophysical environments.

astro-ph.HE↗

arXiv2021

MP3 White Paper 2021 -- Research Opportunities Enabled by Co-locating Multi-Petawatt Lasers with Dense Ultra-Relativistic Electron Beams

Novel emergent phenomena are expected to occur under conditions exceeding the QED critical electric field, where the vacuum becomes unstable to electron-positron pair production. The required intensity to reach this regime, $\sim10^{29}\,\mathrm{Wcm^{-2}}$, cannot be achieved even with the most intense lasers now being planned/constructed without a sizeable Lorentz boost provided by interactions with ultrarelativistic particles. Seeded laser-laser collisions may access this strong-field QED regime at laser intensities as low as $\sim10^{24}\,\mathrm{Wcm^{-2}}$. Counterpropagating e-beam--laser interactions exceed the QED critical field at still lower intensities ($\sim10^{20}\,\mathrm{Wcm^{-2}}$ at $\sim10\,\mathrm{GeV}$). Novel emergent phenomena are predicted to occur in the "QED plasma regime", where strong-field quantum and collective plasma effects play off one another. Here the electron beam density becomes a decisive factor. Thus, the challenge is not just to exceed the QED critical field, but to do so with high quality, approaching solid-density electron beams. Even though laser wakefield accelerators (LWFA) represent a very promising research field, conventional accelerators still provide orders of magnitude higher charge densities at energies $\gtrsim10\,\mathrm{GeV}$. Co-location of extremely dense and highly energetic electron beams with a multi-petawatt laser system would therefore enable seminal research opportunities in high-field physics and laboratory astrophysics. This white paper elucidates the potential scientific impact of multi-beam capabilities that combine a multi-PW optical laser, high-energy/density electron beam, and high-intensity x rays and outlines how to achieve such capabilities by co-locating a 3-10 PW laser with a state-of-the-art linear accelerator.

physics.plasm-ph↗

arXiv2020

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

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.

physics.plasm-ph↗

arXiv2020

Simultaneous compression and opacity data from time-series radiography with a Lagrangian marker

Time-resolved radiography can be used to obtain absolute shock Hugoniot states by simultaneously measuring at least two mechanical parameters of the shock, and this technique is particularly suitable for one-dimensional converging shocks where a single experiment probes a range of pressures as the converging shock strengthens. However, at sufficiently high pressures, the shocked material becomes hot enough that the x-ray opacity falls significantly. If the system includes a Lagrangian marker, such that the mass within the marker is known, this additional information can be used to constrain the opacity as well as the Hugoniot state. In the limit that the opacity changes only on shock heating, and not significantly on subsequent isentropic compression, the opacity of shocked material can be determined uniquely. More generally, it is necessary to assume the form of the variation of opacity with isentropic compression, or to introduce multiple marker layers. Alternatively, assuming either the equation of state or the opacity, the presence of a marker layer in such experiments enables the non-assumed property to be deduced more accurately than from the radiographic density reconstruction alone. An example analysis is shown for measurements of a converging shock wave in polystyrene, at the National Ignition Facility.

physics.comp-ph↗

arXiv2020

Workshop Report: Brightest Light Initiative (March 27-29 2019, OSA Headquarters, Washington, D.C.)

This Brightest Light Initiative (BLI) Workshop Report captures the important research ideas and recommendations for enabling that work developed by over 100 leading scientists at a community-initiated workshop held March 27-29, 2019 in Washington, DC. Workshop attendees developed an understanding of key opportunities, as well as gaps in current technologies and capabilities, for science enabled by the highest-intensity lasers.

physics.plasm-ph↗

arXiv2020

On Seminal HEDP Research Opportunities Enabled by Colocating Multi-Petawatt Laser with High-Density Electron Beams

The scientific community is currently witnessing an expensive and worldwide race to achieve the highest possible light intensity. Within the next decade this effort is expected to reach nearly $10^{24}\,\mathrm{W}/\mathrm{cm^2}$ in the lab frame by focusing of 100 PW, near-infrared lasers. A major driving force behind this effort is the possibility to study strong-field vacuum breakdown and an accompanying electron-positron pair plasma via a quantum electrodynamic (QED) cascade [Edwin Cartlidge, "The light fantastic", Science 359, 382 (2018)]. Whereas Europe is focusing on all-optical 10 PW-class laser facilities (e.g., Apollon and ELI), China is already planning on co-locating a 100 PW laser system with a 25 keV superconducting XFEL and thus implicitly also a high-quality electron beam [Station of Extreme Light (SEL) at the Shanghai Superintense-Ultrafast Lasers Facility (SULF)]. This white paper elucidates the seminal scientific opportunities facilitated by colliding dense, multi-GeV electron beams with multi-PW optical laser pulses. Such a multi-beam facility would enable the experimental exploration of extreme HEDP environments by generating electron-positron pair plasmas with unprecedented densities and temperatures, where the interplay between strong-field quantum and collective plasma effects becomes decisive.

physics.plasm-ph↗

arXiv2019

Equations of state for ruthenium and rhodium

Ru and Rh are interesting cases for comparing equations of state (EOS), because most general purpose EOS are semi-empirical, relying heavily on shock data, and none has been reported for Ru. EOS were calculated for both elements using all-electron atom-in-jellium theory, and cold compression curves were calculated for the common crystal types using the multi-ion pseudopotential approach. Previous EOS constructed for these elements used Thomas-Fermi (TF) theory for the electronic behavior at high temperatures, which neglects electronic shell structure; the atom-in-jellium EOS exhibited pronounced features from the excitation of successive electron shells. Otherwise, the EOS matched surprisingly well, especially considering the lack of experimental data for Ru. The TF-based EOS for Ru may however be inaccurate in the multi-terapascal range needed for some high energy density experiments. The multi-ion calculations predicted that the hexagonal close-packed phase of Ru remains stable to at least 2.5 TPa and possibly 10 TPa, and that its c/a should gradually increase to the ideal value. A method was devised to estimate the variation in Debye temperature from the cold curve, and thus estimate the ion-thermal EOS without requiring relatively expensive dynamical force calculations, in a form convenient for adjusting EOS or phase boundaries. The Debye temperature estimated in this way was similar to the result from atom-in-jellium calculations. We also predict the high-pressure melt loci of both elements.

physics.comp-ph↗

arXiv2018

Observation of ultrafast solid-density plasma dynamics using femtosecond X-ray pulses from a free-electron laser

The complex physics of the interaction between short pulse high intensity lasers and solids is so far hardly accessible by experiments. As a result of missing experimental capabilities to probe the complex electron dynamics and competing instabilities, this impedes the development of compact laser-based next generation secondary radiation sources, e.g. for tumor therapy [Bulanov2002,ledingham2007], laboratory-astrophysics [Remington1999,Bulanov2015], and fusion [Tabak2014]. At present, the fundamental plasma dynamics that occur at the nanometer and femtosecond scales during the laser-solid interaction can only be elucidated by simulations. Here we show experimentally that small angle X-ray scattering of femtosecond X-ray free-electron laser pulses facilitates new capabilities for direct in-situ characterization of intense short-pulse laser plasma interaction at solid density that allows simultaneous nanometer spatial and femtosecond temporal resolution, directly verifying numerical simulations of the electron density dynamics during the short pulse high intensity laser irradiation of a solid density target. For laser-driven grating targets, we measure the solid density plasma expansion and observe the generation of a transient grating structure in front of the pre-inscribed grating, due to plasma expansion, which is an hitherto unknown effect. We expect that our results will pave the way for novel time-resolved studies, guiding the development of future laser-driven particle and photon sources from solid targets.

physics.plasm-ph↗