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 YO4: Transport in HED Plasmas 
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Chair: Matthew Hill, AWE Plc, Aldermaston UK Room: OCC B110112 
Friday, November 9, 2018 9:30AM  9:42AM 
YO4.00001: Experimental observation of nonlocal electron transport in warm dense matter Katerina Falk, Milan Holec, Christopher J Fontes, Christopher L Fryer, Carl W Greeff, Heather M Johns, David S Montgomery, Derek W Schmidt, Michal Šmíd We present the first experimental observation of electron transport in warm dense matter using Xray Thomson Scattering (XRTS) measurement from lowdensity CH foams compressed by a strong laserdriven shock at the OMEGA laser facility [1]. The XRTS measurement was combined with VISAR and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.535 eV in shocked CH foam was measured by XRTS. These measurements were complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. These results were compared to radiation hydrodynamics simulations that include firstprinciples treatment of nonlocal electron transport in WDM with excellent agreement. 
Friday, November 9, 2018 9:42AM  9:54AM 
YO4.00002: Characterizing pressure ionization in ramp compressed Cobalt with electron induced fluorescence spectroscopy Sheng Jiang, Amy Jenei, Philip A Sterne, Stephanie Hansen, Paul Grabowski, Ronnie Lee Shepherd, Ray Smith, Jon Henry Eggert, Yuan Ping The ionization stage constrains the effective Z and free electron density which plays a critical role in transport properties of HED matter. In spite of extensive theoretical and experimental efforts, there is still little consensus on pressure ionization under these extreme pressures and temperatures [1,2]. We have performed an experiment on OMEGA EP to measure ionization in compressed Co as a function of density, using the K shell fluorescence induced by hot electrons generated through shortpulse lasersolid interactions. The high pressure was achieved by ramp compression to keep the temperature below 2eV so as to rule out the effect of thermal ionization. When the Co density rises to about twice its initial value, a small red shift in the Co Kβ peak is observed, along with a shoulder at around 15eV below the main peak. Comparison of the measurement and predictions by different ionization models will be presented. 1. C. A. Iglesias, HEDP, 12, 5 (2014) 2. B.J.B. Crowley, HEDP, 13, 84 (2014) 
Friday, November 9, 2018 9:54AM  10:06AM 
YO4.00003: Relativistic electron beam transport through cold and shockheated vitreous and diamond carbon samples Mathieu BaillyGrandvaux, Christine M Krauland, Joohwan Kim, Mingsheng Wei, Paul Eric Grabowski, Shu Zhang, Joao J Santos, Philippe Nicolaï, Wolfgang R. Theobald, Pierre ForestierColleoni, Farhat N Beg Most short pulse lasermatter interaction experiments studying relativistic electron beam (REB) transport are performed with initially cold targets where the resistivity is far from that in warm dense matter (WDM). However, many highenergydensity (HED) applications, such as fast heating for advanced ICF schemes, rely upon REB transport in the WDM regime. We will present Hybrid PIC simulations using advanced resistivity models in the WDM conditions that are able to reproduce the REB transport measurements performed on the OMEGA EP for a set of cold and shockheated carbon samples. The REB energy distribution and transport were diagnosed using an electron spectrometer and xray fluorescence measurements from a Cu tracer buried at the rear side of the sample. We will show that the resistivity response of the media, which governs the selfgenerated resistive fields, is of paramount importance to understand and correctly predict the REB transport. HED modeling has been hindered by limited understanding of the WDM regime, but our benchmark REB modeling offers some insight into this highly applicable regime. 
Friday, November 9, 2018 10:06AM  10:18AM 
YO4.00004: Measuring the electrical conductivity of warm dense gold using ultrafast THz radiation Zhijiang Chen, Benjamin K OforiOkai, Anthea Weinmann, Lars Seipp, Siegfried Glenzer Electrical conductivity contains important information of warm dense matter (WDM), such as conduction electron density, ionic structure factor, and electronion interaction potentials [1]. With the advent of ultrafast lasers, WDM can be created by isochoric laser excitation of solids, and a great amount of efforts have been made to determine their AC conductivity at optical frequencies [23]. However, the direct measurement of DC conductivity of such WDM is still missing. Recently, we have developed an experimental platform to study the electrical conductivity of laser heated WDM using singleshot THz time domain spectroscopy [45], whose oscillation frequency is significantly below the electronelectron and electronion scattering frequency. This provides a direct approach to determining the DC conductivity of WDM. The experimental results of isochorically heated warm dense gold thin films will be presented and compared with previous studies at optical frequencies.

Friday, November 9, 2018 10:18AM  10:30AM 
YO4.00005: Heatrelease EOS and thermal conductivity of warm dense carbon by proton differential heating Yuan Ping, G Elijah Kemp, Andrew McKelvey, Philip A Sterne, Heather D Whitley, Ronnie Lee Shepherd, Rui Hua, Farhat N Beg, Jon Henry Eggert Measurements of amorphous carbon thermal conductivity at 28 eV temperatures using differential heating platform will be presented. This platform has previously demonstrated such measurements for Al (Y. Ping et al. Phys. Plasmas, 2015; A. Mckelvey, et al. Sci. Reports 2017). A temperature gradient is induced in a Au/C duallayer target by proton differential heating. The subsequent heat flow from the hotter Au to the carbon rear surface is detected by two simultaneous timeresolved diagnostics: streak optical pyrometry for surface temperature and Fourier domain interferometry for surface motion. The comparison between the data and 7 EOS tables shows that only one EOS model can reasonably reproduce all the data. By using a chisquare statistical analysis to quantify the comparison, the thermal conductivity model is constrained with uncertainties down to +10%. 
Friday, November 9, 2018 10:30AM  10:42AM 
YO4.00006: Experimental studies of thermal conductivity in warm dense iron Andrew McKelvey, G. E. Kemp, S. Jiang, R. Shepherd, S. P. HauRiege, H. Whitley, P. Sterne, M. P. Hill, C. R. D. Brown, E. Floyd, J. D. Fyrth, J. W. Skidmore, R. Hua, F. N. Beg, M. Kim, B. Cho, J. Lee, J. King, R. R. Freeman, G. Collins, H. J. Lee, E. Galtier, Y. Ping We present the first experimental thermal conductivity studies of warm dense iron at 0.57.8 g/cc and 35 eV. The experiment used 6.8 keV xrays from the LCLS XFEL to volumetrically heat thin bilayer Au/Fe targets and establish a prompt temperature gradient at the layer interface. Timeresolved diagnostics measure both the thermal selfemission at the target rear surface and the expansion velocity. Data is modeled with a 1D twotemperature hydrodynamics calculation in Hydra. The results are sensitive to EOS, optical opacity, and thermal conductivity; the relative impacts of models for each category will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DEAC5207NA27344 with support from DOE OFES Early Career program. 
Friday, November 9, 2018 10:42AM  10:54AM 
YO4.00007: Abinitio calculation of electronion relaxation in warm dense plasmas Jacopo Simoni, Jerome Daligault The rapidly growing ability to form and probe warm dense matter (WDM) conditions increases the demand for a quantitative predictive modeling of the nonequilibrium processes induced in the target materials. In particular, much uncertainty remains in our understanding of the electronion (ei) energy relaxation timescales as illustrated by the strong disagreements between analytical models and indicated by recent experimental investigations. This reflects both the scarcity of accurate measurements and the difficulty of performing firstprinciple calculations of outofequilibrium processes in the WDM regime. We present the first abinitio calculations of the ei energy relaxation rates, a.k.a. couplings, in WDM. To this end, a Kubo relation for the ei couplings was derived and methods were developed to compute them with quantum molecular dynamics. We discuss the results obtained for several materials (Al, H, Co, and Fe) across a wide range of WDM conditions, including the solid and liquid metal phases traversed in WDM experiments. Our approach serves as a comparison with measurements and model predictions, permits an extension into regimes not covered by experiments, and provides insight into the underlying physics. 
Friday, November 9, 2018 10:54AM  11:06AM 
YO4.00008: Largescale molecular dynamics simulations of electron nonlocal transport Abdourahmane Diaw, Jeff Haack, Jim Cooley Hot, dense plasmas produced during the implosion of inertial confinement fusion (ICF) capsule are characterized by steep temperature and density gradients. Because of these gradients, the thermal meanfree path of the electron becomes large with respect to the characteristic scale length of the temperature. Thus, electrons with meanfree path collisional larger than the scale length can escape gradients before being scattered and depositing their energy into the plasma, leading to a distortion of the distribution function away from Maxwellian. This leads to nonlocal transport of the electrons energy as the electrons are delocalized. In this work, reduced nonlocal electron transport model proposed by Schurtz, Nicolai and Busquet (SNB) [Phys. Plasmas 7, 4238 (2000)] is compared to classical molecular dynamics (MD) simulations. The nonequilibrium classical MD simulations are performed with particles interactions modeled by quantum statistical potentials. Using machine learning algorithms, we improve the SNB model by finding accurate and efficient kernel for the electron heat conduction. 
Friday, November 9, 2018 11:06AM  11:18AM 
YO4.00009: Nonlocal thermal transport in nonLTE plasmas Hai P Le, Mark Sherlock, Howard A Scott Thermal transport and nonLTE kinetics are two important aspects in simulations of inertial confinement fusion (ICF) applications. Electron thermal transport in the presence of large temperature gradients requires a kinetic treatment which takes into account finite collision meanfreepaths. This problem can be simulated with VlasovFokkerPlanck (VFP) models, which evolve the distribution function in phasespace via transport, collisions, and interactions with the electromagnetic field. Although VFP simulations provide an accurate prediction of the heat flow, they require knowledge of the ionization state of the plasma. NonLTE kinetics is simulated with a collisionalradiative (CR) model, which gives the ionization balance, opacities and equation of state. CR models using compact, screened hydrogenic atomic models have proven to be successful in simulating many experiments at the National Ignition Facility (NIF). In this study, we couple a VFP code with a nonMaxwellian, CR kinetics code to simulate electron thermal transport in a nonLTE plasma. The coupling of nonlocal transport and nonLTE kinetics is examined in detail.

Friday, November 9, 2018 11:18AM  11:30AM 
YO4.00010: FirstPrinciples Studies on the Stopping Power of Warm Dense Plasmas with Time‑Dependent OrbitalFree Density Functional Theory Yanhao Ding, S. X. Hu, A. J. White, O. Certik, L. A. Collins Electronic transport properties of warm dense plasmas, such as electrical/thermal conductivities and stopping power, are of particular interest to geophysics, planetary science, astrophysics, and inertial confinement fusion (ICF). One important example is the aparticle stopping power of dense deuterium–tritium (DT) plasmas, which must be precisely known for current smallmargin ICF target designs to ignite. To precisely determine the stopping power of warm dense plasmas, we have developed a timedependent orbitalfree density functional theory (TD‑OFDFT) method for ab initio investigations. Our TDOFDFT calculations have well reproduced the recent well characterized stopping power experiment in warm dense beryllium. For aparticle stopping in warm and solid density DT plasmas, our ab initio TDOFDFT simulations show a lower stopping power up to ~25% compared with two stoppingpower models widely used in the highenergydensity physics community. 
Friday, November 9, 2018 11:30AM  11:42AM 
YO4.00011: ExchangeCorrelation Effects in Screening Models of Dense Plasmas Aditya Savanur, Liam G Stanton, Michael S Murillo Electron screening of ions is among the most fundamental properties of plasmas, determining the effective ionic interactions that impact all properties of a plasma. With the development of experimental facilities that probe high energydensity (HED) physics regimes ranging from warm dense matter to hot dense matter, an accurate and computationally efficient description of dense plasma screening has become essential. We employ the work done by Stanton and Murillo [Phys. Rev. E, 91, 033104 (2015)], which provides a unified framework for screening models based on finitetemperature orbitalfree density functional theory, including gradient corrections and exchangecorrelation effects. Here, we further investigate a variety of exchangecorrelation models, which are rarely used in simple screening models, and quantify the impact of their contributions across the HED regime with applications such as transport and equation of state. The results are compared to numerical calculations from highfidelity physics simulations in the literature. 
Friday, November 9, 2018 11:42AM  11:54AM 
YO4.00012: Developing Consistent Models for Matter in Extreme Conditions Stephanie Hansen, Taisuke Nagayama, Thomas Gomez, Andrew D Baczewski, Attila Cangi The extreme densities and temperatures accessible on modern experimental facilities alter the electronic and ionic structure of materials, leading to changes in state and transport properties that inform both simulations and the interpretation of experimental data. This talk will describe ongoing efforts to generate a comprehensive set of consistent state and transport data from a single atomic model whose electrons and ions respond selfconsistently to changes in local material conditions. This approach ensures that equations of state, transport properties, and diagnostic signatures are mutually consistent. Such consistency can help to constrain simulations and may improve the reliability of data interpretation from complex experiments. 
Friday, November 9, 2018 11:54AM  12:06PM 
YO4.00013: Study of the ExchangeCorrelation Thermal Effects for Transport and Optical Properties of Shocked Deuterium Valentin V. Karasiev, Suxing Hu
Accurate knowledge of equation of state, transport, and optical properties of matter in a wide range of conditions is of growing importance in many areas of research such as planetary science, astrophysics, and inertial confinement fusion. Firstprinciples methods based on density functional theory (DFT) take into account quantum effects that are essential for warm dense matter (WDM). However, the predictive capability of DFT calculations for WDM depends crucially upon having an exchangecorrelation (XC) freeenergy functional accurate across temperature regimes. In this talk, we will briefly discuss some details of the formal developments of the new XC freeenergy functional that bridges lowtemperature (groundstate) and hightemperature (plasma) limits^{1} and therefore takes into account the XC thermal effects. Optical properties of shocked deuterium are calculated within the Kubo–Greenwood formulation with use of the thermal XC functional. The calculated reflectivities of shocked deuterium are compared with recent experiments on OMEGA.
[1] V. V. Karasiev, J. W. Duffy, and S. B. Trickey, Phys. Rev. Lett. 120, 076401 (2018). 
Friday, November 9, 2018 12:06PM  12:18PM 
YO4.00014: Electronic transport coefficients for dense partially degenerate plasma mixtures Jeffrey Haack, Michael Sean Murillo, Cory Hauck In this talk, we derive electronic transport coefficients for dense, partially degenerate plasmas based on the extension of a new multiphysics, conservative, entropic BhatnagarGrossKrook model [1,2] to include quantum effects for the electron species. We compare to the commonly used model Lee and More [3], which uses a simpler Krook model and neglects electronelectron collisions. We also discuss the role of the ionization state ⟨Z⟩ in the validity of these expansions.

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