Bulletin of the American Physical Society
60th Annual Meeting of the APS Division of Plasma Physics
Volume 63, Number 11
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session NO4: Physics of Warm Dense Matter and HEDP |
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Chair: Yuan Ping, Lawrence Livermore National Lab Room: OCC B110-112 |
Wednesday, November 7, 2018 9:30AM - 9:42AM |
NO4.00001: Investigating the insulator to metal transition in dense fluid hydrogen with dynamic compression on NIF P M Celliers, M Millot, A F Goncharov, P Loubeyre, S Brygoo, R S McWilliams, J H Eggert, J R Rygg, S Le Pape, D E Fratanduono, J L Peterson, N B Meezan, G W Collins, R Jeanloz, R J Hemley Despite extensive theoretical and experimental advances in the past decades, the properties of fluid hydrogen remain challenging to understand in the vicinity of the predicted first-order insulator-to-metal transition, also known as the plasma phase transition. Recent static and dynamic compression studies provide evidence for the insulator-metal transition in fluid hydrogen and deuterium at temperatures less than 2000 K but disagree on both the nature and pressure of the transition. There are also discrepancies in theoretical calculations with transition pressures spanning 120 GPa to 400 GPa at these temperatures. We present recent experiments using a reverberation compression scheme on the National Ignition Facility to compress cryogenic deuterium up to 600 GPa at much lower temperatures than along the principal Hugoniot. Our optical measurements reveal a high index of refraction along with the onset of visible absorption, both arising from band gap closure ranging from 120 to 150 GPa (depending on temperature). Metallic reflectivity appears above 1000 K and 200 GPa. These results complement recent static and dynamic compression studies. |
Wednesday, November 7, 2018 9:42AM - 9:54AM |
NO4.00002: Free electron laser probing of warm dense matter created by a laser-driven proton beam Chris McGuffey, Mathieu Bailly-Grandvaux, Eric Galtier, Chandra Curry, Neil B Alexander, Nick Aybar, Krish Bhutwala, Eddie Del Rio, Maylis Dozieres, Brandon Edghill, Pierre Forestier-Colleoni, Maxence Gauthier, Rui Hua, Joohwan Kim, Jongjin B Kim, Haeja Lee, Joseph Strehlow, Yuan Ping, Mingsheng Wei, Siegfried H Glenzer, Gilliss Dyer, Farhat N Beg This covers our first experiment to study proton-heated Warm Dense Matter (WDM) with the Matter in Extreme Conditions (MEC) end station at the LCLS in SLAC National Accelerator Laboratory. The extremely high current-density proton beams that can be created with relativistically-intense lasers grant new capabilities in high energy-density science experiments by isochorically heating matter. Stopping powers for ions in WDM have large uncertainty, limiting our ability to predict the heating that could be achieved with above-mentioned proton beams in experiments and in fusion burn scenarios. To help benchmark our understanding of intense beam heating to the WDM regime, we carried out an experiment using the MEC’s 25 TW, 800 nm short pulse laser and the LCLS free electron laser (FEL). The short pulse irradiated a 5 μm thick Cu foil to create a proton beam that heated foil samples of 0.65 μm Al, 1.2 μm Al, or 4.0 μm polypropylene, which were then probed by the FEL operating at 7.5 keV. We present source and transmitted proton spectra as well as the first attempts to measure X-ray Thomson scattering from the heated volume to characterize its temperature and density. |
Wednesday, November 7, 2018 9:54AM - 10:06AM |
NO4.00003: Time and spatially-resolved density measurement of Proton-heated Warm Dense Silica using Phase Contrast X-ray imaging Maxence Gauthier, Emma McBride, Eric Flint Cunningham, Chandra Curry, Adrien Descamps, Gilliss Dyer, Mungo Frost, Luke Fletcher, Eric Galtier, Griffin Glenn, Philip Heimann, Jongjin B Kim, Mianzhen Mo, Benjamin K Ofori-Okai, Frank Seiboth, Franziska Treffert, Siegfried Glenzer Understanding warm dense matter, a complex state of matter lying between condensed matter physics and plasma physics is highly relevant for a number of fields including modeling the evolution and structure of large planets and stellar surface transport properties. The complicated interplay between physical processes in the WDM state make it particularly difficult to model theoretically. Furthermore, the extreme temperature-density space where WDM resides is challenging to create experimentally. Among all the methods, laser-produced proton heating has shown to be one of the best to generate uniform and solid-density warm sample. So far, the warm dense conditions achieved are typically inferred from changes in reflectivity or by changes in X-ray absorption (XANES), rather than measured. Here, we report experimental results obtained at the MEC end-station (SLAC), in which a 20 µm thick, 100 µm wide silicon target is heated by a broadband and energetic protons beam generated by a 15 TW short pulse laser. The density spatial and temporal evolution of the heated sample is measured through transverse phase contrast X-ray imaging using the 50 fs duration X-ray free electron laser operated at 11 keV. The ion beam spectrum is characterized using an absolutely calibrated Thomson parabola |
Wednesday, November 7, 2018 10:06AM - 10:18AM |
NO4.00004: Progress towards characterizing large volumes of WDM heated with a monochromatic electron beam Joshua Coleman, Heidi E Morris, Heather L Andrews, James P Colgan, Payson Dieffenbach, Micah Jakulewicz, Dustin Offermann, John Perry, Nick Ramey, Thomas Schmidt, Dale Welch Record levels of warm dense matter have been created at a mass and volume of 22 mg and 2.5 x 10-3 cm3 with a monochromatic electron beam. The hydrodynamic motion of the material has been characterized through the heating process utilizing photonic Doppler velocimetry (PDV). A quantitative set of hydro models using the particle beam energy deposition package in LASNEX indicate comparable expansion to those measured with PDV. These models confirm the slow heating process and pressure release at P > 200 kbar. In addition models indicate once the material transitions into the warm dense phase it lasts for >150 ns; providing the flexibility to study large volumes of this phase on long time scales. Additional diagnostics are under development to measure the WDM including X-ray Thomson scattering, X-ray absorption spectroscopy, and X-ray imaging. Preliminary measurements of the expanding density gradient will be presented which are critical for confirming the lifetime and cutoff region of the warm dense phase compared to detailed LASNEX simulations. |
Wednesday, November 7, 2018 10:18AM - 10:30AM |
NO4.00005: Melting dynamics of femtosecond laser-irradiated tungsten with non-intrinsic defects Mianzhen Mo, Samuel Murphy, Zhijiang Chen, Paul Fossati, Renkai Li, Yongqiang Wang, Xijie Wang, Siegfried Glenzer Understanding the structural dynamics of fs laser-induced melting is crucial in the study of a wide range of applications from laser micro-machining to high energy density physics experiments. While much attention has been given to melting dynamics of bulk crystals and thin films, little work has been done on understanding the melting dynamics in materials containing non-intrinsic defects, such as materials in the extreme radiation environments of a fusion reactor. Here we present an ultrafast-electron-diffraction study of fs laser-induced melting in solids with highly populated non-intrinsic defects. The incorporation of these non-intrinsic defects were obtained through high-energy ion irradiation of W. Diffraction experiments show that W subjected to 10 displacement per atom of damage undergoes a melting transition within 10ps. In contrast, the un-irradiated target still displays considerable crystallinity on timescales in excess of 20ps. The observed rapid melting of radiation-damaged W is confirmed by two temperature molecular dynamics simulations revealing the crucial role of defect clusters, particularly nanovoids, in driving the ultrafast melting process. These studies provide atomic-level insights into the ultrafast melting of materials with highly-populated defects. |
Wednesday, November 7, 2018 10:30AM - 10:42AM |
NO4.00006: Clocking Femtosecond Collisional Dynamics via Resonant x-ray Spectroscopy Quincy van den Berg, Elisa V. Fernandez-Tello, Patrick Hollebon, Hyun-Kyung Chung, T. Burian, Ulf Zastrau, George Dakovski, Michael Minitti, Alberto de la Varga, Justin Stephen Wark, Vojtech Vozda, Jaromir Chalupsky, Richard Lee, Thomas Preston, Jacek Krzywinski, Pedro Velarde, Sam M Vinko Electron-ion collisional dynamics is of fundamental importance in determining plasma transport properties, non-equilibrium plasma evolution and electron damage in diffraction imaging applications using bright x-ray free-electron lasers (FELs). Here we describe the first experimental measurements of ultra-fast electron impact collisional ionization rates using resonant core-hole spectroscopy in a solid-density magnesium plasma, created and diagnosed with the Linac Coherent Light Source x-ray FEL. By resonantly pumping the 1s-2p transition in highly-charged ions within an optically-thin plasma we have measured how off-resonance charge states are populated via collisional processes on femtosecond times scales. We present a collisional cross section model that matches our results and demonstrates how the cross sections are enhanced by dense-plasma effects including ionization potential lowering. Non-LTE (local thermodynamic equilibrium) collisional radiative simulations show excellent agreement with the experimental results, and provide new insight on collisional ionization and threebody-recombination processes in the dense plasma regime. This work has recently been published in Physical Review Letters 120, 055002 (2018). |
Wednesday, November 7, 2018 10:42AM - 10:54AM |
NO4.00007: Measurements of non-resonant inelastic X-ray scattering from warm dense Argon plasmas at the LCLS Luke Fletcher, Emma McBride, Bastian Witte, Thomas G White, Chandra Curry, Adrien Descamps, Maxence Gauthier, Sebastian Goede, Jongjin B Kim, Bob Nagler, Benjamin K Ofori-Okai, Alex Rigby, Peihao Sun, Ulf Zastrau, Gianluca Gregori, Siegfried Glenzer Measuring bound-free transitions from X-ray Thomson scattering, or non-resonant inelastic X-ray scattering from core or semi-core electrons, is a powerful technique to probe matter in extreme conditions. Here we present measurements of high signal-to-noise, spectrally resolved inelastic X-ray scattering from shock compressed Argon at the MEC end-station of the LCLS. Combining a coherent X-ray laser coupled with a novel Argon micro-jet that is shock-heated using a 1 Hz temporally stretched Ti:Saphire laser has enabled dynamic measurements of ionization, densities, and temperatures from ps-laser driven samples approaching the warm dense state. Our results show time resolved measurements of heated Argon using spectrally resolved X-ray scattering with unprecedented dynamic range. Measurements were performed using a energy-dispersive spectrometer equipped with a Highly Annealed Pyrolytic Graphite (HAPG) crystal in combination with a Cornell-SLAC Pixel Array Detector (CSPAD) that was configured in the von Hamos geometry. |
Wednesday, November 7, 2018 10:54AM - 11:06AM |
NO4.00008: Ab initio data for the uniform electron gas at warm dense matter conditions Michael Bonitz, Tobias Dornheim, Simon Groth Further progress in the field of warm dense matter (WDM) requires accurate data on the electron component. I summarize our recent results on computing ab inito thermodynamic data for the uniform electron gas (UEG) that cover the whole temperature-density range and arbitrary spin polarizations [1]. The results are based on a combination or two novel quantum Monte Carlo (PIMC) methods (Permutation blocking PIMC and configuration PIMC) which avoids the notorious fermion sign problem, without invoking uncontrolled approximations such as the fixed node approximation. Furthermore, a new finite-size correction scheme has been developed that allows to compute thermodynamic data in the thermodynamic limit without loss of accuracy. The result is an analytical parametrization of the exchange–correlation free energy that is the key input for the simulation of real warm dense matter applications, e.g., via thermal density functional theory. |
Wednesday, November 7, 2018 11:06AM - 11:18AM |
NO4.00009: Checking the Salpeter enhancement of nuclear reactions in asymmetric mixtures Jean Clerouin, Nicolas Desbiens, Philippe Arnault, Alexander White, Christopher Ticknor, Joel David Kress, Lee A. Collins We investigate the plasma enhancement of nuclear reactions in the intermediate coupling regime using orbital free molecular dynamics (OFMD) simulations. We study mixtures of H-Cu and H-Ag as prototypes of weakly and strong coupling limits due to the charge asymmetry. Of particular importance, is the partial ionization of Cu and Ag and the free electron polarization constitutive of OFMD simulations. By comparing a series of OFMD simulations at various concentration and constant pressure to multi-component hyper netted chain (MCHNC) calculations of effective binary ionic mixtures (BIM), we set a general procedure for computing enhancement factors. The MCHNC procedure allows to extend the range of the study to very low concentrations (5% or less) and to very high temperatures (few keV) unreachable by molecular dynamics simulations. Enhancement factors for nuclear reactions rates extracted from the MCHNC approach are compared with the Salpeter theory in the weak and strong coupling regime, and an interpolation is proposed.
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Wednesday, November 7, 2018 11:18AM - 11:30AM |
NO4.00010: Fast Non-Adiabatic Warm Dense Matter Simulation Brett Larder, Scott Richardson, Dirk Gericke, Gianluca Gregori When constructing modern simulations of Warm Dense plasma, one must make compromises in accuracy so that the calculations are computationally accessible. To access long-time ion correlations, the Born-Oppenheimer approximation is usually relied upon so that simulations can be performed at the time scale of the ions. |
Wednesday, November 7, 2018 11:30AM - 11:42AM |
NO4.00011: Investigation of coated surface ablation in the thick regime on pulsed-power drivers Matthew Evans, Roman V Shapovalov, Imani West-Abdallah, James Young, Pierre-Alexandre Gourdain Recent studies have proposed developing warm dense matter (WDM) using pulsed-power drivers. Pulsed-power drivers use magnetic fields to compress matter into the Mbar regime, relaxing the confinement time necessary to reach the mesoscale. The purpose of this campaign is to study the properties of bulk materials in WDM samples on longer time scales. Surface ablation from a thick conductor such as a rod offers new, unpredictable current paths, ultimately leading to very disparate, mixed states, that hinder the measurements of the properties of WDM samples. The addition of coating prevents the formation of ablated plasma around the conductor and has proven to reduce expansion. The damping layer limits the current to flow very close to the conductor surface, reducing parasitic current flows outside of the conductor, allowing full control of the magnetic field topology by the shape of the conductor alone. Reducing expansion and preventing surface ablation allows for greater magnetic pressure during the compress phase. We propose investigating the surface ablation in the visible regime to determine the temperature and resistivity of these samples. An analysis of coated surface ablation on Al rods in the visible spectrum is presented here. |
Wednesday, November 7, 2018 11:42AM - 11:54AM |
NO4.00012: The impact of surface coating on plasma ablation in magnetic anvil cells Pierre-Alexandre Gourdain, Marissa B Adams, Gilbert W Collins, Matthew T Evans, Siegfried Glenzer, Hannah R Hasson, Adam Sefkow, Charles E Seyler, Imani West-Abdallah, James R Young Dielectric coatings have shown great promises in quenching plasma ablation, generated by the large current densities so commonly found in fast z-pinches. Once plasma ablation is reduced to a minimum, the current is constrained to only flow near conductors, giving exquisite control over the magnetic field. This control allows not only for more symmetric implosions, but also for more complex magnetic field typologies. We present here how different coating configurations impact the final pressure and homogeneity of warm dense matter samples using PERSEUS, an extended MHD code. Dropping the nonphysical vacuum resistivity, this code allows to study in great details how coating resistivity impacts the compression of the warm dense matter samples. |
Wednesday, November 7, 2018 11:54AM - 12:06PM |
NO4.00013: Considerations for verification, validation, and uncertainty quantification (VV&UQ) in high-energy-density physics simulations Aaron Koskelo, Brandon M Wilson, John L Kline, Joshua P Sauppe Due to its complex, nonlinear multiphysics and difficulty to reach important regimes in an experimental setting, the HEDP community readily accepts advanced computational modeling. With the increased use of modeling and simulation, (M&S) comes a responsibility to quantify our predictive confidence with respect to the modeling applications. The framework for quantifying our predictive confidence falls under the umbrella of verification, validation, and uncertainty quantification (VV&UQ). The engineering community has long recognized the importance of VV&UQ and ASME is working towards standardizing the field. In this talk, we discuss considerations for conducting VV&UQ in the field of HEDP. |
Wednesday, November 7, 2018 12:06PM - 12:18PM |
NO4.00014: Towards designing high-energy-density physics experiments for model validation Brandon M Wilson, Aaron Koskelo, John L Kline, Joshua P Sauppe HEDP experiments can be designed for three purposes: scientific discovery, model development, and validation. HEDP validation experiments are the least common and, too often, inadequately characterized for model validation. Reasons include:
We suggest, with conscientious design and enhanced cooperation between experimentalists and model developers, current HEDP experiments can also realize validation requirements. Six validation experiment design requirements from Oberkampf and Roy [1] are presented; special considerations for HEDP experiments regarding these requirements are discussed using examples. 1. Oberkampf, William L., and Christopher J. Roy. Verification and validation in scientific computing. Cambridge University Press, 2010. |
Wednesday, November 7, 2018 12:18PM - 12:30PM |
NO4.00015: Scaling of High Energy Density Physics experiments John Kline, Aron M Wilson, Aaron Koskelo, Joshua P Sauppe, David Allen Osthus, Scott Alan Vander Wiel, Nelson M Hoffman, Gowri Srinivasan Two laser facilities with a large difference in laser energy is a capability in the US that offers a unique opportunity to evaluate physics scaling in the HED regime. Based on observations, typical experiments do not scale from the Omega laser facility to the National Ignition Facility even though the targets only vary by a factor of 2-3x in size. While differences in the laser energy deposition do play a role, the variation in experimental parameters change significantly enough to modify the importance of various physics models in simulation codes. Understanding the differences and designing experiments across these scales provide a unique opportunity for model validation, as well as applying uncertainty quantification to evaluate confidence in models outside the domain where data exists. In this presentation, we will discuss challenges and opportunities for scaling from Omega to NIF and how this can be applied for both model validation and uncertainty quantification. |
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