Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Plasma Physics
Volume 66, Number 13
Monday–Friday, November 8–12, 2021; Pittsburgh, PA
Session UO03: HED: Laboratory AstrophysicsOn Demand
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Chair: Derek Schaeffer Room: Rooms 302-303 |
Thursday, November 11, 2021 2:00PM - 2:12PM |
UO03.00001: Exploring the universe through Discovery Science on the National Ignition Facility (NIF)* Bruce Remington Highlights from the NIF laser Discovery Science program will be presented. Examples include experiments on nuclear reactions relevant to stellar nucleosynthesis [1]; equations of state (EOS) at ultrahigh pressures (1-800 Mbar) relevant to planetary interiors and cores [2- 4] and white dwarf envelopes [5, 6]; radiative shock stabilized Rayleigh-Taylor (RT) instabilities relevant to supernova remnants [7, 8]; long duration, ablation-front RT experiments [9, 10]; relativistically hot plasmas [11]; magnetic reconnection at high energy density (HED) conditions [12]; and high velocity, low density interpenetrating plasmas relevant to collisionless astrophysical shock formation and particle acceleration mechanisms [13]. |
Thursday, November 11, 2021 2:12PM - 2:24PM |
UO03.00002: Extracting quantitative properties of radiative shocks on the National Ignition Facility Heath J LeFevre, Kevin H Ma, Mike J MacDonald, Tilo Doeppner, Marius Millot, Channing M Huntington, Paul A Keiter, Eric Johnsen, Carolyn C Kuranz Radiative shocks occur throughout the universe in supernovae, supernova remnants, and accretion shocks. It is possible to create radiative shocks using high-energy laser facilities such as the National Ignition Facility (NIF). |
Thursday, November 11, 2021 2:24PM - 2:36PM |
UO03.00003: Improvements to the NIF opacity platform Theodore S Perry, Robert F Heeter, Heather M Johns, Yekaterina Opachich, Harry F Robey, Evan Dodd, Natalia Krasheninnikova, Thomas Day, Chris J Fontes, Lynn Kot, Todd Urbatsch, Melissa R Douglas, Brian G Wilson, Carlos A Iglesias, Eric Dutra, Matt S Wallace, Daniel C Mayes, Don E Winget, Michael H Montgomery, James E Bailey National Ignition Facility (NIF) experiments to measure the x-ray opacity of elements important to the flow of energy in astrophysical systems and other high energy density plasma have been underway for a number of years. In the past year significant improvements have been made to the platform to reduce backgrounds, increase signal strength, expand the spectral coverage of the spectrometer, and increase the range of temperatures and densities over which the measurements can be taken. This presentation will describe these improvements and show the most recent data from experiments on oxygen and iron opacities. This work was performed under the U.S. Department of Energy LANL contract 89233218CNA000001, LLNL Contract No. DE-AC52-07NA27344, Sandia Contract No. DE-AC04-94AL85000, NNSS Contract No. DE-AC52-06NA25946, and Unversity of Texas Contract No. DE-NA0003843. |
Thursday, November 11, 2021 2:36PM - 2:48PM |
UO03.00004: Density measurements for the NIF Iron Opacity Campaign Yekaterina Opachich, Robert F Heeter, Heather M Johns, Evan S Dodd, John L Kline, Natalia Krasheninnikova, Todd Urbatsch, Theodore S Perry The Opacity Platform on the National Ignition Facility (NIF) has been developed to measure iron opacities at varying densities and temperatures relevant to the solar interior, and to verify recent experimental results obtained at the Sandia Z-machine, which diverge from theory. The first set of NIF experiments collected iron opacity data at ~150-160 eV, and an electron density of ~7x1021 cm-3, with a goal to study temperatures up to ~210 eV, with electron densities of up to ~3x1022 cm-3. The platform has a unique capability that allows an in-situ measurement of the sample expansion. The sample expansion data is used to infer the sample density thorughout the duration of the laser drive. We present the details of the density measurement technique, data analysis and recent results. |
Thursday, November 11, 2021 2:48PM - 3:00PM |
UO03.00005: Low Energy Design of the National Ignition Facility’s Soft X-ray Opacity Spectrometer Matt S Wallace, Robert F Heeter, James Heinmiller, Eric Dutra, Russell Knight, Raul Lara, Alice Durand, Don Max, Eric Huffman, Jay Ayers, Jim A Emig, Thomas Archuleta, Todd Urbatsch, Ted S Perry The soft x-ray Opacity Spectrometer (OpSpec) used on the National Ignition Facility (NIF) has recently incorporated elliptically shaped crystals. The use of an elliptically shaped crystal allows an acceptance aperture at the crossover focus between the crystal and the detector, which reduces background and eliminates nearly all reflections from alternate crystal planes. The success of the original elliptical geometry in the opacity experiments has driven the design of a new elliptical geometry with a spectral range of 520-1100 eV. Coupled with the original elliptical geometry the new lower energy ellipse can cover the full iron L-shell and major oxygen transitions that are important to solar opacity experimentation. The new design has been built and tested on a Henke x-ray source, showing the desired spectral coverage. Recently the new geometry has been fielded on NIF opacity experiments. The new geometry, Henke testing, and preliminary results from opacity experiments are presented. |
Thursday, November 11, 2021 3:00PM - 3:12PM |
UO03.00006: Higher order and penumbral blurring correction methodology for Opacity spectrometer used on the NIF Eric Dutra, Joseph S Cowan, James Emig, Chris J Fontes, Robert F Heeter, Yekaterina P Opachich, Harry F Robey, Matthew S Wallace, Ted S Perry The Opacity Spectrometer (OpSpec) used on the NIF’s opacity experiments have gone through several iterations to help improve the signal to noise ratio by lowering background, alternate crystal planes reflections, and improvements in the spectral resolution, which help to increase the validity of the opacity measurements. However, higher order reflections are intrinsic to the crystal and the photon energy of the source. The opacity spectrometer measures x-ray spectra from the different experimental regions: the backlight source, emission source, and the absorption region. The transmission calculated from these regions is a convolution of the penumbra and higher order reflections effects. This work represents our result in deconvolving the 2nd and 3rd order spectral energy corrections with a penumbral de-blurring to correct the relative measurement of x-ray intensity of different spectral energies. |
Thursday, November 11, 2021 3:12PM - 3:24PM |
UO03.00007: Opacity-on-NIF Sample Design Ethan Smith, Kyzer Gerez, Todd Urbatsch, Natalia Krasheninnikova Models of proposed new targets and configurations used in National Ignition Facility (NIF) experiments to measure the x-ray opacity of elements are demonstrated and discussed. Different methods of arranging the components of the targets are explored for increasing the density and temperatures in the targets while keeping the targets uniform and in local thermal equilibrium and maintaining an optimal transmission. This work will describe the outcomes of these computational experiments using Cassio, an Eulerian radiation-hydrodynamics code. |
Thursday, November 11, 2021 3:24PM - 3:36PM |
UO03.00008: Opacity-on-NIF Backlighter Design Kyzer Gerez, Ethan Smith, Natalia Krasheninnikova, Todd Urbatsch Stronger backlighters are needed as iron opacity experiments at the National Ignition Facility (NIF) approach higher temperatures and densities. Cassio was used to explore backlighter design, simulate capsule implosions, and calculate signal output. Cassio is an Eularian radiation-hydrodynamics code developed at Los Alamos to study high-energy-density physics. The code was used to determine how variations of the geometries, capsule thicknesses, density gradients, and laser details affect backlighter performance. FESTR, a spectral postprocessor, was also used to obtain detailed, time-dependent spectral output from the Cassio simulations. |
Thursday, November 11, 2021 3:36PM - 3:48PM |
UO03.00009: Modeling the Thermal Cooling Instability with CRASH Rachel Young, Matthew Trantham, Carolyn C Kuranz We will present the results of one and two-dimensional (1D and 2D) simulations of the thermal cooling instability using CRASH, the University of Michigan's radiation hydrodynamics code. We achieve conditions susceptible to the thermal cooling instability by colliding two high-speed plasma flows head-on. The shock structure that forms between the two colliding plasma flows features two radiative shock fronts and a cold, dense post-shock region between them. The thermal cooling instability manifests itself in the radiative shocks, which undergo temperature cycles. We will show that these temperature cycles drive compression waves into the cold dense post-shock layer. |
Thursday, November 11, 2021 3:48PM - 4:00PM |
UO03.00010: Strong Suppression of Heat Conduction in Laser-Driven Magnetized Turbulent Plasmas Petros Tzeferacos, Jena Meinecke, James S Ross, Archie Bott, Scott Feister, Hye-Sook Park, Tony Bell, Robert Bingham, Alexis Casner, Dustin H Froula, Michel Koenig, Chikang Li, Yingchao Lu, Charlotte A Palmer, Richard Petrasso, Hannah Poole, Bruce Remington, Brian Reville, Adam Reyes, Alexandra Rigby, Dongsu Ryu, Francesco Miniati, Subir Sarkar, Alexander A Schekochihin, Don Q Lamb, Gianluca Gregori Astronomical observations of galaxy-cluster cores reveal temperatures that are significantly higher than expected from the relatively short radiative-cooling time scales. While the central active galactic nuclei are thought to provide most of the heating, the presence of stochastic magnetic fields at equipartition with the kinetic energy of the turbulent motions is expected to impact thermal transport. We present laser-driven experiments by the Turbulent Dynamo collaboration at LLNL’s National Ignition Facility that realize magnetized turbulence and plasma properties relevant to those in galaxy clusters. The experiments, designed with high-fidelity FLASH simulations, demonstrate a strong suppression of local heat transport by two orders of magnitude or more. The suppression results in pronounced temperature fluctuations at small spatial scales, akin to the cold fronts observed in galaxy-cluster plasmas. |
Thursday, November 11, 2021 4:00PM - 4:12PM |
UO03.00011: Numerical Modeling of Laser-Driven Plasma Experiments Aiming to Study Turbulent Dynamo and Thermal Conduction at the National Ignition Facility Yingchao Lu, Scott Feister, Jena Meinecke, Francesco Miniati, Gianluca Gregori, Archie Bott, Adam Reyes, Edward C Hansen, J.T. Laune, Brian Reville, James S Ross, Don Q Lamb, Petros Tzeferacos Dynamo in astrophysical turbulence is a key process for the amplification of magnetic fields in the early universe. The advent of high-power laser systems, along with the scaling of magnetohydrodynamics (MHD), has made it possible to recreate astrophysical conditions and processes in terrestrial laboratories. We present 3-D radiation-MHD FLASH simulations used to design and interpret laser-driven plasma experiments of fluctuation dynamo at Lawrence Livermore National Laboratory’s National Ignition Facility. The experiments aim to demonstrate dynamo amplification in the large magnetic Prandtl number regime, which is relevant for magnetic-field amplification in galaxies and galaxy clusters. The simulations show that the experiments can achieve a turbulent plasma state with magnetic Reynolds numbers in excess of 10^4 and magnetic Prandtl numbers above unity. The dynamo-amplified magnetic fields in the simulations are strong enough that the electron Larmor radius is smaller than the mean free path in the turbulent plasma. The suppression of electron heat transport under such conditions is incorporated in the simulations by switching off the electron conductivity to assess its effects on the plasma properties. |
Thursday, November 11, 2021 4:12PM - 4:24PM |
UO03.00012: Experimental evidence of early-time linear-saturation of the ion-Weibel instability in counterstreaming plasmas Mario J Manuel, May Ghosh, Raghuram Jonnalagadda, Farhat N Beg, Marissa B Adams, Petros Tzeferacos, Channing M Huntington, Bruce Remington, James S Ross, Dmitri D Ryutov, Hong W Sio, George F Swadling, Scott Wilks, Hye-Sook Park The ion-Weibel instability is a leading candidate mechanism for the formation of collisionless shocks observed in many astrophysical systems. Experimental and computational studies have shown that the ion-Weibel instability drives current filamentation in counterstreaming plasma flows with the capability to mediate collisionless shock formation and subsequent particle acceleration in the lab. The present work focuses on the study of nonlinear ion-Weibel evolution under various plasma conditions through utilization of different ion species and experimental geometries. Path-integrated B-field distributions are retrieved from experimental proton images and Fourier analyzed to compare with linear theory based on benchmarked radiation-hydrodynamic simulations. The new analyses presented here indicate that the first ~400ps of the collisionless interaction between the two flows dominates the spectral evolution of Weibel filaments, with typical wavelengths of ~300μm and B-field amplitudes of ~1-3T. |
Thursday, November 11, 2021 4:24PM - 4:36PM |
UO03.00013: Collisionless shock gas jet experiments at OMEGA Tim M Johnson, Graeme Sutcliffe, Jacob A Pearcy, Andrew Birkel, Vladimir Tikhonchuk, Joseph Katz, Richard Petrasso, Chikang Li We report OMEGA experiments utilizing a gas jet system to produce and study collisionless shocks. A hollow CH hemisphere is illuminated with lasers to produce a supersonic plasma flow. The plasma flow collides with a hydrogen gas jet and the two plasmas interact to form a collisionless shock. Imaging Thomson scattering measurements clearly show density and temperature jumps. Density increases by a factor of about 3 and temperature by a factor of about 5. The plasma flow velocity is measured to be greater than 1500 km/s leading to carbon-carbon collision mean free path of about 2 cm which is much larger than the shock front thickness (about 100 um). This indicates that the system is collisionless. Proton radiography data show a shock structure that evolves in time. |
Thursday, November 11, 2021 4:36PM - 4:48PM |
UO03.00014: Simulations of electron injection in collisionless shocks for conditions relevant to NIF experiments Anna Grassi, George F Swadling, Hans Rinderknecht, Dmitri D Ryutov, Drew P Higginson, Hye-Sook Park, Anatoly Spitkovsky, Frederico Fiuza Collisionless shocks are ubiquitous in astrophysical plasmas and are known to be important in magnetic field amplification and in the acceleration of both high-energy electrons and protons (cosmic rays). While the theory of diffusive shock acceleration (DSA) is well established, the details of particle injection into DSA remain a long-standing puzzle, particularly for electrons. Very recently, laser-driven high-energy-density experiments at the National Ignition Facility (NIF) have observed for the first time high-Mach number Weibel-mediated collisionless shocks and the associated nonthermal electron acceleration. We will discuss results from large-scale particle-in-cell simulations of counter-streaming plasma flows for the conditions of the NIF experiments. This study reveals that electrons can be effectively injected by multiple scatterings in small-scale turbulence produced within the shock front via a first order Fermi mechanism. We will present detailed analysis of the characteristic diffusion properties and energization associated with this mechanism, and discuss its relevance to electron injection in young supernova remnant shocks. |
Thursday, November 11, 2021 4:48PM - 5:00PM |
UO03.00015: Effect of radiation reaction on slowdown in unmagnetized kinetic shocks Kevin Schoeffler, Elisabetta Boella, Nitin Shukla, Luis O Silva The slowdown of unmagnetized plasmas via the generation of kinetic shocks is studied using particle-in-cell (PIC) simulations in various parameter regimes. The degree of slowdown caused by shocks generated by two cold interpenetrating pair plasmas is compared with that from shocks generated by a sharp boundary of a hot dense plasma and a colder tenuous plasma. In the first case, the slowdown is primarily caused by the generation of magnetic fields via the Weibel/ filamentation instability. In the second case, which can be realized in the lab using high-powered lasers interacting with near-solid density targets, an electrostatic shock is generated. Collisions between the electrostatic shocks also lead to magnetic fields via the Weibel instability. The plasma's interaction with these electromagnetic fields is the major cause of slowdown. However, with the most powerful lasers available today it may be possible that the electromagnetic fields and the energy of plasma become significantly large such that radiation reaction will begin to play an important role in the slowdown. We investigate the importance of the radiation reaction on the slowdown taking advantage of PIC simulations that self-consistently include the Landau Lifshitz radiation reaction forces on the plasma. |
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