Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session UO06: Warm Dense MatterLive Streamed
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Chair: Suxing Hu, LLE Room: Ballroom 111 C |
Thursday, October 20, 2022 2:00PM - 2:12PM |
UO06.00001: Ionization states of carbon ions from shock compressed CH foams measured with X-ray Thomson scattering at the National Ignition Facility Luke Fletcher, Bruce A Remington, Tilo Doeppner, C. A Di Stefano, Dirk Gericke, Siegfried H Glenzer, Mike J MacDonald Accurate equation of state (EOS) measurements in the warm dense matter (WDM) regime are extremely difficult to achieve due to the small volumes and short lifetimes of the systems typically created in laboratory experiments. Temperatures and ionization states are particularly challenging quantities to measure accurately in the WDM regime, yet they significantly affect the properties of matter at extreme conditions. High precision temperature measurements at these conditions are needed to improve EOS models used in inertial confinement fusion simulations and the modeling of planetary interiors. Here we will present the recently developed the Colliding Planar Shocks (CPS) platform on the NIF with the goal of creating large volumes of highly compressed matter with minimal spatial gradients to make high precision measurements of materials under extreme conditions. State variables such as the electron temperatures, electron densities, and ionization states can be extracted using simultaneous X-ray Thomson scattering (XRTS) and X-ray radiography. Initial experiments using the CPS platform have recently demonstrated the ability to compress solid CH and CH foams 3–8 times solid densities, as well as reach electron temperatures between 10-50 eV, and material pressures of 10–100 Mbar. |
Thursday, October 20, 2022 2:12PM - 2:24PM |
UO06.00002: Coupling Shock Compression and Ultrafast X-ray Heating to Observe New Phase Transitions Nicholas J Hartley, Siegfried H Glenzer, Kento Katagiri, Kohei Miyanishi, Norimasa Ozaki, Claudia C Parisuana-Barranca, Emma E McBride Ultrafast heating by intense X-ray pulses is capable of driving rapid, nonthermal phase changes in materials. This is most obvious in covalently-bonded materials, where the excitation of large numbers of electrons out of the valence band can induce Coulomb forces between the ions, and drive rearrangement into a closer-packed structure. |
Thursday, October 20, 2022 2:24PM - 2:36PM |
UO06.00003: Non-isotropic Atomic Motion in Warm Dense Carbon Philip Heimann, Nicholas J Hartley, Ichiro Inoue, Andre F Antoine, Fabien Dorchies, Roger Falcone, Jérôme Gaudin, Hauke Hoeppner, Yuichi Inubushi, Hae Ja Lee, Vladimir Lipp, Paloma Martinez, Nikita Medvedev, Franz Tavella, Victor Tkachenko, Sven Toleikis, Makina Yabashi, Toshinori Yabuuchi, Jumpei Yamada, Beata Ziaja-Motyka X-ray Free Electron Laser (XFEL) radiation can transform carbon into a warm dense matter state. Two X-ray pulses were used; the first as pump to reach the warm dense matter state and the second as probe performing X-ray diffraction. The experiment was performed at the SACLA XFEL facility at the beamline 3 experimental hutch 5. The samples were polycrystalline diamond. The pump and probe photon energies were 7 and 10.5 keV, respectively, and the delay between the X-ray pulses was varied from 0 to 286 fs. To provide a range of energy densities, the X-ray focus was adjusted between 150 nm and 1 μm. The (111), (220) and (311) diffraction peaks were observed. The intensity of each diffraction peak decreased with time indicating a disordering of the crystal lattice. From a Debye-Waller analysis, the root-mean-square (rms) atomic displacement perpendicular to particular lattice planes are calculated. At higher fluences, the rms atomic displacement perpendicular to the (111) planes is significantly larger than that perpendicular to the (220) or (311) planes. By accepting two successive XFEL pulses at a time delay of 33 ms, graphite (002) diffraction was observed beginning at a threshold dose of 1.5 eV/atom. The experimental results will be compared with calculations using a hybrid model based on tight-binding molecular dynamics. |
Thursday, October 20, 2022 2:36PM - 2:48PM |
UO06.00004: Developing x-ray Fresnel Diffractive-Refractive Radiography for Measuring Thermal Conductivity in Warm Dense Matter Cameron H Allen, Matthew Oliver, Laurent Divol, Travis D Griffin, Andreas J Kemp, Gregory E Kemp, Otto L Landen, Yuan Ping, Markus O Schoelmerich, Wolfgang R Theobald, Tilo Doeppner, Thomas G White Transport properties in warm dense matter (WDM), such as thermal conductivity, have extensive theoretical predictions but lack experimental benchmarking [1]. We have developed a Fresnel Diffractive Radiography (FDR) platform at the Omega Laser Facility, which enables high spatial resolution measurements of the evolution of an isochorically-heated WDM interface [2]. Novel 1 µm-wide slits provide a spatially coherent x-ray source that, in the presence of sharp density gradients, result in distinct diffraction fringes. Isochoric x-ray heating of CH-coated metal wires sets up a temperature differential at the material interface. After pressure equilibration, the interface is hydrodynamically-stable, and the evolution of the interface is driven primarily through thermal conduction, which modifies the temperature and density profiles. From the resulting shape of the diffraction fringes the thermal conductivity of the materials can be inferred. |
Thursday, October 20, 2022 2:48PM - 3:00PM |
UO06.00005: Disentangling the Effects of Non-Adiabatic Interactions upon Ion Dynamics within Warm Dense Hydrogen William A Angermeier, Brett Scheiner, Thomas G White, Nathaniel R Shaffer Warm dense matter (WDM) is a complex state that inhabits the region of parameter space connecting condensed matter to classical plasma physics. In this intermediate regime, we investigate the significance of non-adiabatic electron-ion interactions on ion dynamics. We directly compare diffusivity from the non-adiabatic electron force field (eFF) computational model to an adiabatic molecular dynamics (MD) simulation to disentangle electron-ion interactions. A tabulated potential developed through a force matching algorithm ensures the only difference between the models is due to the electronic motion. We implement this new method to characterize non-adiabatic effects on the diffusivity of warm dense hydrogen over a wide range of temperatures and densities and find that non-adiabatic effects may be more important for lower densities and temperatures. However, for thermodynamic conditions where experimental electron-ion equilibration data exists, we find non-adiabatic effects play little role, with only a 1.5% change due to non-adiabatic electron-ion interactions. |
Thursday, October 20, 2022 3:00PM - 3:12PM |
UO06.00006: Study of self-consistent target heating and resistive field evolution driven by intense proton beams in dense plasmas Krish A Bhutwala, Joohwan Kim, Christopher McGuffey, Mark Sherlock, Mathieu Bailly-Grandvaux, Farhat N Beg Intense proton beams have numerous potential scientific applications, including radiography and deflectometry, cancer therapy, warm dense matter generation, and inertial confinement fusion. With recent advancements in beam focusing mechanisms and energy conversion efficiency, the current densities of laser-driven proton beams approach 1010 A/cm2, intense enough to induce strong resistive magnetic fields that may affect beam propagation within metals. Here, we give a theoretical model that can estimate the evolution of the resistive magnetic fields induced by intense proton beams (∼109-1010 A/cm2) in aluminum. The analysis utilizes resistivity and heat capacity models applicable from cold solid to hot plasma regimes, so that the field evolution is valid through and above the warm dense matter regime. The magnetic field profile is theoretically calculated for both monoenergetic and Maxwellian beam distributions, and the roles of various beam parameters are investigated. The model shows that Maxwellian proton beams with temperature 5 MeV and total energy 10 J may generate up to 150 T fields in aluminum. Comparison of theoretical results with 2-D hybrid-PIC simulations shows good agreement and sheds light on the model’s theoretical limitations. |
Thursday, October 20, 2022 3:12PM - 3:24PM |
UO06.00007: Investigation of phonon hardening in laser-excited gold using in-situ single-shot X-ray diffraction at the LCLS. Adrien Descamps, Benjamin K Ofori-Okai, Zhijiang Chen, Luke Fletcher, Siegfried H Glenzer, Nicholas J Hartley, Jerome B Hastings, Dimitri Khaghani, Mianzhen Mo, Bob Nagler, Vanina Recoules, Ronald A Redmer, Maximilian Schörner, Peihao Sun, Thomas G White, Emma E McBride The use of ultra-short, ultra-bright X-ray pulses generated at X-ray Free Electron Laser (XFEL) light sources coupled with high-intensity femtosecond optical pulses has enabled the investigation of ultrafast phenomena taking place in warm dense matter. In such experiments, the optical laser pulse transfers its energy primarily to the electronic system which reacts almost instantaneously. The subsequent response of this far-from-equilibrium state of matter strongly depends on the excitation conditions. Density functional theory simulations performed on laser excited Au have suggested that the lattice undergoes a near-instantaneous hardening of its interatomic potential when electrons are heated to ~6 eV, and known as phonon hardening [1, 2]. This behavior is expected to have a significant impact as phonons contribute to intrinsic thermodynamic quantities such as constant-volume specific heat, entropy, and would also affect the melting behavior. |
Thursday, October 20, 2022 3:24PM - 3:36PM |
UO06.00008: Measuring the Electron-Ion Equilibration Rate in Warm Dense Metals with High-Resolution Inelastic X-ray Scattering Daniel Haden, Thomas G White, Eric Galtier, Hae Ja Lee, Dimitri Khaghani, Lennart Wollenweber, Sameen Yunus, Adrien Descamps, Ben Armentrout, Carson Convery, Jacob M Molina, Karen Appel, Eric Cunningham, Luke Fletcher, Sebastian Goede, Jerome B Hastings, Emma E McBride, Giulio Monaco, Ulf Zastrau, Dirk Gericke, Siegfried H Glenzer, Gianluca Gregori, Bob Nagler When a high-intensity laser hits a solid target, the preferential and rapid heating of one subsystem over the other creates a highly non-equilibrium state [1,2]. These transient, high-energy-density plasmas are a precursor to warm dense matter and serve as a testbed where we can validate quantum mechanical theories of electron-ion interactions. We have implemented a high-resolution (∼50meV) x-ray scattering platform [3], designed for use with free-electron lasers, with a resolution capable of measuring the quasi-elastic Rayleigh peak. Essentially governed by Doppler broadening, the peak's width is a direct measurement of the ions' velocity distribution and corresponds to a model-independent ion temperature measurement. We have measured the rise of the ion temperature in a variety of laser-excited metals (Au, Ag, Cu, and Ti) over the first ∼20 ps after irradiation, during which the ions are rapidly heated to electronvolt temperatures. The extracted electron-ion equilibration rates are compared to several theoretical and computational models. |
Thursday, October 20, 2022 3:36PM - 3:48PM |
UO06.00009: Development of a Machine-Learning–Based Ionic-Force Correction Model for Quantum Molecular-Dynamic Simulations of Warm Dense Matter Joshua Hinz, Valentin V Karasiev, Suxing Hu, Deyan Mihaylov Affordable calculations of accurate ionic forces are a key component of quantum molecular-dynamic (MD) simulations used to investigate warm-dense-matter systems. Within the Born–Oppenheimer approximation, Kohn–Sham (KS) density functional theory (DFT) offers such a balance for the calculation of the electronic contribution to the total ionic forces. Unfortunately, because of the computational cost of KS-DFT scaling as the cube of the system temperature, KS-DFT tends toward a prohibitive cost above 5 eV. Alternatively, orbital-free (OF) DFT is orders of magnitude faster, but its accuracy only converges with that of KS-DFT above ~15 eV. In this work we have developed a machine-learning–based model that uses ionic configurations to predict the difference in the ionic forces between KS and OF-DFT for a given ion. This allows OF ionic forces to be corrected in order to achieve KS accuracy with minimal additional cost. We will discuss the development of a new set of descriptors for the ionic configurations as well as provide training and testing results of the model for hydrogen at 1.0 g/cm3 between 3 and 15 eV. Furthermore, MD simulations are performed with the model and validated against reference KS results. |
Thursday, October 20, 2022 3:48PM - 4:00PM |
UO06.00010: Equation of State Measurements for Proton Heated Warm Dense Matter on the OMEGA-EP Sheng Jiang, Amy E Lazicki, Matthew P Hill, Damian C Swift, Joseph Nilsen, Philip A Sterne, Heather D Whitley, Jon H Eggert, Alison Saunders, John J Ruby, Richard A London, Alexandre Do, Yuan Ping Understanding the behavior of materials in the warm dense matter regime can significantly extend the knowledge in fields ranging from astrophysics to high energy density physics. Of particular importance is understanding the equation of state (EOS), which describes the relationship between pressure, volume, temperature, and the internal energy of a system at a state of thermodynamic equilibrium. We demonstrate the measurement of release isentrope of warm dense aluminum heated isochorically by a proton beam generated by the OMEGA EP short-pulse laser. We have used specially designed targets to guide the protons so that we can reach different initial temperatures. Three EP long-pulse beams were used to heat an X-ray backlighter to provide an X-ray source for streaked X-ray radiography. Various backlighter energies were used to cover a wide range of densities. Following a method derived by Foord et al. [1], we can analyze the results accurately enough to obtain a pressure-density isentrope curve for benchmarking various EOS models. |
Thursday, October 20, 2022 4:00PM - 4:12PM |
UO06.00011: Diamond Formation in Reshocked Epoxy Michelle C Marshall, Martin G Gorman, Danae Polsin, Jon H Eggert, Mary Kate Ginnane, J. Ryan Rygg, Gilbert W Collins, Lara Leininger We present measurements of diamond formation in doubly shocked Stycast 1266 epoxy (comprising C, H, Cl, N, and O) using in-situ x-ray diffraction. Epoxy samples were reshocked against a LiF window to 80 and 148 GPa in experiments at the Omega Laser Facility. The pressure and temperature conditions were diagnosed in situ using velocimetry and optical pyrometry, respectively. X-ray diffraction patterns of the compressed epoxy are consistent with cubic diamond. These results, in combination with previous works on CH, CH2, CH4, and methane hydrate, indicate that diamond formation from carbon and hydrogen-based compounds is commonplace at the extreme conditions associated with ice giant planet interiors and that the chemical composition, thermodynamic compression path, and kinetics play an important role. |
Thursday, October 20, 2022 4:12PM - 4:24PM |
UO06.00012: The Impact of Magnetic Fields on the Melting Curves of Warm Dense Matter Irem Nesli Erez, Pierre-Alexandre Gourdain, Riccardo Betti, Jonathan L Peebles, Jonathan R Davies We propose an experimental setup to study the melting curves of a warm dense matter sample under magnetization and demonstrate that such a setup is possible based on PERSEUS simulations. The setup proposed involves a 1/2 hohlraum (halfraum) illuminated by OMEGA beams in a polar drive arrangement. While the material is expanding, the ablated plasma moves inwards due to the rocket effect compressing the initial magnetic field of 50 T generated by MIFEDS to up to 1 kT based on our simulations. This field strength is needed in order to magnetize the valence electrons of warm dense matter. We further show that the density of the plasma between the sample and the compression beam is sub-critical allowing the compression beam to reach the target. For the diagnostics, PXRDIP will be used to study how and when the state transition occurs with MIFEDS off (no magnetization) and MIFEDS on (magnetization). Our simulations promise successful experiments to study the melting curves of warm dense matter under magnetization, which are of critical importance to understanding the inner structure of astrophysical objects like white dwarfs and are of help to ongoing research on fusion science. |
Thursday, October 20, 2022 4:24PM - 4:36PM |
UO06.00013: Computational modeling of scattering processes in warm dense beryllium Brian Robinson, Alina Kononov, Andre Schleife, Andrew D Baczewski, Stephanie B Hansen Accurate predictions of electrical and thermal conductivities play an important role in the design of inertial confinement fusion (ICF) targets, where they can affect compression, instability growth, and energy losses. The warm dense matter (WDM) regime, with near-solid densities and temperatures above ~1 eV (10 kK), is particularly difficult to model due to the confluence of degeneracy, thermal, and strong coupling effects. Here, we study electron-electron (el-el) and electron-phonon (el-ph) scattering processes in beryllium, a common ICF material, in the WDM regime from first principles. Specifically, we find el-el lifetimes by fitting the imaginary part of the self-energy from many-body perturbation theory GW calculations to the Landau theory of the Fermi liquid. From this data, we predict el-el lifetimes on the order of hundreds of fs near the Fermi energy and tens of fs under excitations of 1 eV. We also simulate time-dependent el-ph relaxation dynamics by solving the Boltzmann transport equation, helping us to disentangle the relative importance of both processes. Revelations from this work will improve collision frequencies and scattering cross sections entering conductivity models used for ICF target design. |
Thursday, October 20, 2022 4:36PM - 4:48PM |
UO06.00014: Femtosecond visualization of non-equilibrium warm dense copper using x-ray absorption spectroscopy Gyeongbo Kang, Gyusang Lee, Changhoo Lee, Ahhyun Seong, Robert Carley, Loic L Guyader, Martin Teichmann, Giuseppe Mercurio, Benjamin V Kuiken, Andreas Scherz, Byoung-ick Cho In this contribution, we present the femtosecond XANES measurements of highly non-equilibrium copper (Ed = 0.127~1.27 MJ/kg), which is heated with frequency-doubled Ti:Sapphire laser pulse and evolves to warm dense matter. The experiment is performed at the European XFEL facility. A transmission zone plate is used to split and focus two identical XFEL beams (±1st order) and allow a single-shot-based measurement with high S/N ratios. X-ray absorption is measured in a broad range of photon energy around Cu L3-edge (E-EF = -4.5~10.5 eV) with 100 fs resolution. The evolution of pre-edge absorption visualizes the thermalization process between non-equilibrium electron and hole populations in the femtosecond regime. The detailed dynamics can be described with a modified multi-temperature model considering the dynamical band shifts and bond-hardening effect. The evolution of NEXAFS visualizes the lattice vibration and melting process in picosecond time scales. |
Thursday, October 20, 2022 4:48PM - 5:00PM |
UO06.00015: Ultrafast melting of Warm Dense Cu studied by x-ray spectroscopy Michal Smid, Alexander Köhler, Brant Bowers, Yen-Yu Chang, Jurjen P. Couperus Cabadag, Lingen Huang, Michaela Kozlová, Thomas Kurz, Maxwell Laberge, Xiayun Pan, Pablo Perez-Martin, Isaac L Ruiz de los Panos, Susanne Schöbel, Jan Vorberger, Omid Zarini, Thomas E Cowan, Ulrich Schramm, Arie Irman, Katerina Falk We present novel experimental results of ultra fast heating of Warm Dense Cu diagnosed by means of x-ray absorption and emission spectroscopy carried out at the Draco laser facility at HZDR in 2021. A thin Cu foil was directly heated to few eV temperature by an ultra short laser pulse (40 fs, 2e15 W/cm2) and probed with variable delay in the range 0.2-20 ps by a laser-driven betatron radiation. This betatron radiation, created by a laser wakefield accelerator, is an unique x-ray source with its ultra short duration and broadband spectrum, therefore ideally suited for studies of non-equilibrium dense plasmas while its high brightness allows for single-shot measurement. The sample is studied via the X-ray absorption spectroscopy in the region above the Cu K-edge. This method provides temporally-resolved information about both the ionic structure of the matter and its temperature during the process of ultrafast heating and melting of the material. The measured spectra are understood and analyzed by using Ab initio simulations and the temporal evoution of heatig and melting is compared to PIC simulations to infer the electron to ion energy transer. |
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