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 GM10: Mini-Conference: Charged Particle Transport in High-Energy-Density Plasma ILive Streamed
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Chair: Heather Whitley, LLNL; Suxing Hu, LLE Room: 206 CD |
Tuesday, October 18, 2022 9:30AM - 9:35AM |
GM10.00001: Introduction
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Tuesday, October 18, 2022 9:35AM - 10:05AM |
GM10.00002: Transport coefficient challenges in high energy density plasmas Brian M Haines Coefficients for thermal and particle transport in high energy density (HED) plasmas play a critical role in computational modeling of HED experiments. Radiation hydrodynamics simulations are our primary tool for such modeling due to the complexity and computational expense of more detailed methodologies. Nevertheless, such simulations typically rely on single material tables or asymptotic formulae to obtain coefficients for transport phenomena. These coefficients are frequently used beyond the domains where they are constrained by data and their uncertainties are often masked by adjusting simulation parameters. Indeed, the uncertainties are large enough that they could play a key role in explaining many remaining discrepancies between simulations and experiments. Several examples of recent work that explore these sensitivities and experimental evidence for the importance of expanding and improving available coefficients will be presented. In some cases, the impact of material configurations at scales below the computational grid size is more important than single material coefficient values. Detailed comparisons between simulation and experiment exhibit deficiencies in shock and viscosity modeling[1,2], a need to better constrain thermalization[3], strong sensitivities to conductivity coefficients[4,5], a need for the development of strategies to modify coefficients in the presence of magnetic fields[6], etc. [1]Gatu Johnson et al, HEDP 36:100825, 2020 [2]Haines et al, Phys Plasmas 21:092306 2014 [3]Haines et al, Nature Comm 11:544 2020 [4]Haines et al, Phys Plasmas in review 2022 [5]Dhakal et al, Phys Plasmas 26:092702 2019 [6]Sadler et al, Phys Plasmas 27:072707 2020 |
Tuesday, October 18, 2022 10:05AM - 10:17AM |
GM10.00003: Charged Particle Transport with Average Atoms Charles Starrett By thermodynamically averaging over all atoms in a plasma, we can define an average atom, with an average electronic structure. Such models have existed since at least the 1940’s, and are still very useful. Though they are principally used for EOS, it turns out that average atom models are also very useful for calculating charged particle transport properties. In this talk I will summarize our efforts in this area, including ionic transport (diffusion, viscosity, etc) and electron transport (i.e., conductivity), highlighting the successes and limitations or our approach. |
Tuesday, October 18, 2022 10:17AM - 10:29AM |
GM10.00004: Efficient Model for Electronic Transport in High Energy-Density Plasmas Liam G Stanton, George M Petrov, Michael S Murillo A model for the efficient calculation of electronic transport coefficients in dense plasma mixtures is presented. The model makes use of cross sections to capture strong scattering effects, pseudopotentials for core electron physics, and both response functions and structure factors to account for many-body effects. These models are kept minimal in complexity to both reduce the number of ad hoc parameters as well as allow for a more straightforward generalization to multi-component systems; however, the model is also wide-ranging enough to span the parameter space and generate multiple transport coefficients self-consistently without the use of a Coulomb logarithm. In particular, electronic viscosities, stopping powers, and electrical and thermal conductivities are calculated together from the same microphysical input quantities. Comparisons with datasets that resulted from a recent transport coefficient workshop and molecular dynamics simulations are made, where strong agreement is often found with higher-fidelity models despite the simplicity of the model [1, 2]. |
Tuesday, October 18, 2022 10:29AM - 10:41AM |
GM10.00005: Electron–Electron Scattering in Dense Plasma Transport: Why it Matters, Why it is Difficult, and What We Can Do About it Today Nathaniel R Shaffer, Katarina A Nichols, Suxing Hu, Charles Starrett In the theory of plasma electron transport coefficients, a long-standing problem is a general and accurate account of electron–electron scattering effects. Historically, plasma kinetic theory has been the tool of choice to understand and quantify these effects. This line of research furnished valuable analytic results for classical and degenerate plasmas alike; however, they only hold for conditions of weak coupling and complete ionization. Over the past two decades, two promising and thus far complementary tracks have been developed. One is large-scale density functional theory (DFT)-based simulations with a Kubo–Greenwood treatment of electron transport. The other is advances in kinetic theory to treat non-ideal conditions, including generalized linear response approaches as well as mean-force kinetic theory. The successes and shortcomings of each approach will be summarized, with special attention paid to the fundamental and practical challenges that arise in trying to capture electron–electron scattering. Promising avenues for development on each track will be discussed, as well as prospects for combining DFT simulations and quantum kinetic theory for a high-fidelity model electron–electron scattering relevant to nonlocal transport effects. |
Tuesday, October 18, 2022 10:41AM - 10:53AM |
GM10.00006: Absorption Measurements Validate the Langdon Factor and Discriminate Between Coulomb Logarithms David Turnbull, Joe Katz, Avi L Milder, Mark Sherlock, David J Strozzi, William Armstrong, Laurent Divol, Dana H Edgell, Russell K Follett, Suxing Hu, Pierre A Michel, Dustin Froula Inverse-bremsstrahlung absorption was measured based on transmission through a finite-length plasma that was well characterized using imaging Thomson scattering. Expected absorption was calculated using the diagnosed plasma conditions while varying the Coulomb logarithm treatment and the use of the Langdon absorption-reduction factor. The experimental data are well reproduced only when using both the Langdon factor and the Johnston-Dawson Coulomb logarithm. The Lee-More Coulomb logarithm—which is widely used in radiation-hydrodynamics codes to simulate inertial confinement fusion implosions—predicts almost 50% more absorption than was observed. |
Tuesday, October 18, 2022 10:53AM - 11:05AM |
GM10.00007: Break
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Tuesday, October 18, 2022 11:05AM - 11:17AM |
GM10.00008: Differential heating platform for thermal conductivity measurements in high-energy-density matter Yuan Ping, Sheng Jiang, Hong W Sio, Amalia Fernandez, Sebastien Hamel, Tadashi Ogitsu, Ronnie L Shepherd, Otto L Landen, Tilo Doeppner, Philip A Sterne, Heather D Whitley Transport measurements are very challenging in HED matter, especially in the warm dense matter regime. This talk will give a brief summary of recent efforts on thermal conductivity study using the differential heating platform [1] in a few materials including aluminum [2], carbon [3] and iron [4,5]. Various techniques have been developed at different facilities for detecting temperature and small spatial scale-lengths in order to infer thermal conductivity, such as ultrafast streaked optical pyrometry [2], refraction-enhanced radiography [6], Fresnel Diffractive Radiography [7], X-ray absorption near-edge structure (XANES) [4,5] and Extended X-ray absorption fine structure (EXAFS) [8]. Experimental results, challenges and future directions will be discussed. |
Tuesday, October 18, 2022 11:17AM - 11:29AM |
GM10.00009: Characterization of the Thermal Conductivity of CH and Be by Refraction-Enhanced X-ray Radiography with a Deep Neural Network analysis Sheng Jiang, Otto L Landen, Heather D Whitley, Sebastien Hamel, Richard A London, Daniel S Clark, Philip A Sterne, Stephanie B Hansen, Suxing Hu, Gilbert W Collins, Yuan Ping The thermal conductivity in the warm dense matter regime is critical for inertial confinement fusion experiments as it can impact the growth of hydro-instabilities at the ablator-fuel interface of the imploding capsule. Understanding it will also significantly extend the limits of knowledge in plasma physics as well as in other areas, such as astrophysics, planetary physics, geophysics and material science. We report the first measurement of thermal conductivity of CH and Be in the warm dense matter regime using a novel experimental platform based on x-ray differential heating and time-resolved refraction-enhanced radiography (RER). Additionally, we have developed a novel technique based on a deep neural network to retrieve the detailed interface density profiles. Our results indicate that the thermal conductivity of CH at about 8 eV at solid density is in reasonable agreement with four most widely used models but a correction term from electron-electron collisions has to be included. However, none of these models agree with the Be thermal conductivity in the range of 4–5 eV. |
Tuesday, October 18, 2022 11:29AM - 11:41AM |
GM10.00010: Measuring Dynamic Properties of Warm Dense Matter with High-Resolution Inelastic X-ray Scattering Thomas G White, Daniel Haden, Emma E McBride, Karen Appel, Ben Armentrout, Florian Condamine, Carson Convery, Eric Cunningham, Chandra Breanne Curry, Francesco Dallari, Adrien Descamps, Luke Fletcher, Stefan Funk, Eric Galtier, Maxence Gauthier, Dirk Gericke, Sebastian Goede, Jerome B Hastings, Dimitri Khaghani, Jongjin B Kim, Haeja Lee, Jacob M Molina, Giulio Monaco, Benjamin K Ofori-Okai, Hannah Poole, Christopher Schoenwaelder, Peihao Sun, Thomas Tschentscher, Bastian Witte, Sameen Yunus, Lennart Wollenweber, Ulf Zastrau, Siegfried H Glenzer, Bob Nagler, Gianluca Gregori Warm dense matter (WDM) is a complex state of matter where strong ion-ion coupling combined with the quantum behavior of the electron fluid make simulation and modeling challenging; experimental verification in this regime is essential. X-ray scattering experiments, which utilize high-intensity beams of penetrating radiation to probe the micro-structure and dynamics, allow for critical testing of our simulations. I will provide an overview of our high-resolution (∼50 meV) X-ray scattering platform, designed for use with free-electron lasers, with a resolution capable of measuring the quasi-elastic Rayleigh peak (in the non-collective regime) and discerning ion modes (in the collective regime). In the first case, we have directly measured the electron-ion equilibration rate in various laser-excited metallic thin films (Au, Ag, Cu, and Ti). In the latter, we have successfully measured the sound speed in warm dense methane. |
Tuesday, October 18, 2022 11:41AM - 11:53AM |
GM10.00011: Probing thermal transport using Extended X-ray Absorption Fine Structure at the National Ignition Facility Hong W Sio, Yuan Ping, Andrew Krygier, Dave Braun, Robert E Rudd, Stanimir Bonev, Gregory E Kemp, Marius Millot, Dayne E Fratanduono, Federica Coppari, Nobuhiko Izumi, Bernard Kozioziemski, Hye-Sook Park, Marilyn B Schneider, James M McNaney, Warren W Hsing, Jon H Eggert, Lan Gao, Kenneth W Hill, Phillip Efthimion Thermal transport measurements in dynamically compressed materials is important to understand thermal conductivity and equilibration rates in high-energy-density plasmas. In experiments performed at the National Ignition Facility (NIF), Extended X-ray Absorption Fine Structure (EXAFS) has been measured and used to constrain temperature, density, and phase in Cu near 400 GPa. These fine-structure modulations in the x-ray absorption are caused by photoelectron scattering off nearby atoms, and are sensitive to both local atomic spacing and thermal disorder. Measured EXAFS signals reveal an unexpected temperature sensitivity to the material layers adjacent to the Cu sample, and motivate the use of K-edge EXAFS as a temperature probe in thermal conductivity studies. |
Tuesday, October 18, 2022 11:53AM - 12:05PM |
GM10.00012: Measuring the dynamic viscosity of HED fluids Jessica Shang, Nitish Acharya, Afreen Syeda, Danae Polsin, J. Ryan Rygg, John J Ruby, David A Chin, Hadley Pantell, Riccardo Betti, Gilbert W Collins, Peter M Celliers, Arianna Gleason, Hussein Aluie The mixing and transport of fluids at high pressures and temperatures can be found in applications ranging from planetary interiors to inertial confinement fusion. However, despite the role that viscosity has on the evolution of hydrodynamic instabilities and energy transfer in turbulence, experimental measurements of viscosity of materials at high energy-density (HED) conditions are limited in parameter space. Calculating viscosity from theory is also challenging, particularly in the warm dense matter regime. In this talk, we present preliminary results from experimental and modeling campaigns at OMEGA and EP that use two methods to infer the dynamic viscosity of dynamically-compressed fluids. In the first technique, we use x-ray radiography to measure the displacement of accelerating microspheres in solid hydrocarbon epoxy (CH). The microsphere trajectory is corroborated with an unsteady forcing model to obtain the epoxy's dynamic viscosity from viscous force contributions. The viscosity is estimated to be less than 10 Pa-s. In the second technique, we use VISAR to measure the velocity of a shock front in a fused silica sample machined with a sinusoidal perturbation. Viscosity is expected to modify the evolution of the decaying shock front at different perturbation wavelengths. Refinements and limitations to the application of these viscometry platforms to HED fluids will also be discussed. |
Tuesday, October 18, 2022 12:05PM - 12:17PM |
GM10.00013: At the Nexus of Modelling and XFEL Experimental Design to Study Diffusion at Warm Dense Conditions Tomorr Haxhimali, Robert E Rudd, James N Glosli, Michael P Surh, Catherine Burcklen, Stefan P Hau-Riege We present results of modelling of diffusive interface broadening between diffusion couple materials in plasma generated in x-ray free electron laser (XFEL) experiments. This numerical study has spanned a range of T from 1 eV up to 50 eV. |
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