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 TO4: Hydrodynamics in HED Plasmas |
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Chair: Heather Johns, Los Alamos National Lab Room: OCC B110-112 |
Thursday, November 8, 2018 9:30AM - 9:42AM |
TO4.00001: The MARBLE Campaign - Overview Brian J. Albright, Thomas J Murphy, Melissa Douglas, Tana Cardenas, James Hamilton Cooley, Thomas H Day, Carlos Di Stefano, Robert A. Gore, Mark Gunderson, Jeff Haack, Brian Michael Haines, Christopher E Hamilton, Yongho Kim, Matthew N Lee, John A Oertel, Richard E Olson, Randall B Randolph, Rahul C Shah, Joseph M Smidt, Lin Yin MARBLE is a separated reactants campaign on the NIF that seeks to investigate the effects of heterogeneous mix on thermonuclear burn. MARBLE uses Si-doped plastic capsules filled with deuterated plastic foam and cryogenic hydrogen-tritium gas fills. Embedded in the foam are “macro-pores,” engineered voids in the foam of known sizes and locations, which allow for control of the level of heterogeneity prior to hydrodynamic mixing. In MARBLE implosions, the ratio of DT to DD neutron yield is measured, from which the degree to which material has mixed atomically can be deduced. The MARBLE team has successfully completed a one-shock platform development campaign on the NIF that demonstrated the ability to field and diagnose thermonuclear burn in engineered foam capsules. Initial results from the newly initiated MARBLE two-shock campaign will also be discussed. |
Thursday, November 8, 2018 9:42AM - 9:54AM |
TO4.00002: Results from Marble Experiments on the National Ignition Facility: One- and Two-Shock Implosions for Studying the Effect of Heterogeneous Mix on Thermonuclear Burn Thomas J Murphy, Brian James Albright, Melissa Douglas, Tana Cardenas, James Hamilton Cooley, Thomas H Day, Mark Gunderson, Jeff Haack, Brian Michael Haines, Christopher E Hamilton, Yongho Kim, Matthew N Lee, John A Oertel, Richard E Olson, Randall B Randolph, Joseph M Smidt, Lin Yin The Marble campaign on NIF [T J Murphy et al, J Phys:Conf Series 717, 012072 (2016)] investigates the effect of heterogeneous mix on thermonuclear burn for comparison to a probability distribution function (PDF) burn model. [J R Fincke, unpublished; J R Ristorcelli, Phys Fluids 29, 020705 (2017)] MARBLE utilizes plastic capsules filled with deuterated plastic foam and tritium gas. A campaign has been completed using the indirect drive exploding pusher platform [S. LePape et al, Phys Rev Lett 112, 225002 (2014)] in which the Marble capsules were driven with a single strong shock. The ratio of DT to DD neutron yield is consistent with uniform atomic mix regardless of the initial morphology of the foam. A new campaign, using the 2-shock platform, has been successful at achieving cooler, denser implosions with similar yields. The status of these experiments will be presented. |
Thursday, November 8, 2018 9:54AM - 10:06AM |
TO4.00003: Flux-throttled Radiation Flow in a Foam Tube Kevin Driver, Josh Kallman, Klaus Widmann, Shon T. Prisbrey We have established a high energy density campaign to study the robustness of supersonic, diffusive radiation flow in experiments at the National Ignition Facility (NIF). The target package is comprised of a silica foam tube with tantala foam walls, which is exposed to a radiation drive of ~200 eV, created by a laser-driven hohlraum. Heated tantala walls minimize radiation loss from the flow inside silica [1]. We throttle the radiation flux entering the silica tube by using blocking washers of various widths. A measurement of radiation flow breakout then provides an experimental scenario for validating radiation hydrodynamics codes. Here, we present 2D, pre-shot radiation hydrodynamics simulations that have guided the design of upcoming experiments. We show that radiation flow fails to reach breakout once the blocking washer covers 50% of the silica annular width. One shot has been performed for the unblocked setup (N170806-004), and our simulation results compare well with the radiation flow timing and flux measurements in that case. [1] O. A. Hurricane and J. H. Hammer, Phys. Plasmas 13, 113303 (2006). |
Thursday, November 8, 2018 10:06AM - 10:18AM |
TO4.00004: Ablator equivalency measurements for Shock-driven Rayleigh-Taylor/Richtmyer-Meshkov experiments Sabrina R Nagel, Channing M Huntington, Jason D. Bender, Kumar S. Raman, Ted Baumann, David J Erskine, Stephan A MacLaren, Shon T. Prisbrey, Ye Zhou The study of hydrodynamic instabilities such as singly or multiply shocked Rayleigh-Taylor/Richtmyer-Meshkov systems usually uses an x-ray opaque, denser material to track the perturbed interface that is driven into a lower density, more transparent material. To avoid 3D effects a center region of the denser material is usually isolated by using a doped tracer strip. Recent experiments even use doped and undoped regions of denser materials side by side for a single measurement. Interchangeability of the undoped, more transparent (here, Polyamide-Imide) and the doped, more opaque (here, CHI) materials is usually assumed. Here we present experimental measurements that check the equivalency of the tracer layer and surrounding material by examining the shock breakout and velocity. These measurements lay the foundation for many shock-driven Rayleigh-Taylor and Richtmyer-Meshkov experiments.
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Thursday, November 8, 2018 10:18AM - 10:30AM |
TO4.00005: High-resolution imaging of the Rayleigh-Taylor Vortex Breakdown at the National Ignition Facility Adrianna Angulo, Channing M Huntington, Sabrina Nagel, Jason Bender, Kumar S. Raman, Carolyn C Kuranz The Rayleigh-Taylor (RT) instability is heavily studied in the high-energy-density physics community, but there remains much potential for improvement in imaging small-scale vortex structures generated at the RT spike tip. The National Ignition Facility (NIF) is capable of delivering accelerated flows driven by strong shocks to study these hydrodynamically unstable systems with unprecedented clarity. Previous works utilized diagnostics with insufficient spatial resolution to observe the detailed morphology of RT spikes as they evolve through the nonlinear regime and transition to turbulence. This talk will demonstrate that the newly installed Crystal Backlighter Imager (CBI) is capable of resolving scales in the inertial subrange, a feature expected in high-Reynolds-number flows. It is shown that by adapting a well-characterized NIF platform to accommodate the CBI, higher-resolution radiography can be obtained for benchmarking simulations of instability growth and the transition to turbulence. |
Thursday, November 8, 2018 10:30AM - 10:42AM |
TO4.00006: Omega 60 experiments of Rayleigh-Taylor instability growth in the highly non-linearly stage: results and future directions Laura Elgin, Timothy A Handy, Guy Malamud, Channing M Huntington, Sallee Klein, Matthew Trantham, R. Paul Drake, Assaf Shimony, Carolyn C Kuranz Potential flow models predict that a Rayleigh-Taylor unstable system will reach a terminal velocity (and constant Froude number). When the density contrast of the two fluids is small, numerical simulations show a re-acceleration of Rayleigh-Taylor Instability (RTI) growth and higher Froude in the late nonlinear stage. We have conducted a series of experiments at Omega 60 to measure single-mode RTI growth to the latest times possible, for both high- and low-Atwood number systems. Experimental results, comparisons with simulations, and future directions are discussed here. |
Thursday, November 8, 2018 10:42AM - 10:54AM |
TO4.00007: A Thin Feedthrough Richtmyer-Meshkov Experiment at the NIF Tiffany Desjardins, Carlos Di Stefano, Kirk Flippo, Elizabeth Merritt, Derek W Schmidt, Thomas H Day, Barbara DeVolder, Forrest W Doss The Richtmyer-Meshkov instability (RMI) arises when a shock crosses the boundary between materials of disparate densities. In an ICF capsule, the boundary between the thin ablator layer and cold fuel can give rise to the RMI. RMI leads to large bubbles and spikes, causing mixing between the ablator and fuel, reducing performance. Secondary shocks from the source, as well as rarefactions and reflections within the capsule can drive the RMI into a turbulent state, further degrading the performance. The Mshock platform is studying the RMI in a thin layer similar to an ICF capsule, but in a planar geometry. The goals are to understand how the instability is affected not only by initial conditions, but how it responds to being shocked multiple times. Recent experiments at NIF have tested the feedthrough of two initial conditions with a similar single mode perturbation, but a different broadband profile with a shock and re-shock setup. The results indicate that the mixing is highly dependent on the initial condition. Detailed analysis and comparison with LANL’s BHR mix model are currently underway. This talk will discuss the platform and experimental results, and give a preliminary comparison with the BHR mix model. |
Thursday, November 8, 2018 10:54AM - 11:06AM |
TO4.00008: Exploring the late time asymptotic evolution of Rayleigh-Taylor instability via NIF discovery science experiments Assaf Shimony, Dov Shvarts, Guy Malamud, Yonatan Elbaz, Channing M Huntington, Stephan A MacLaren The late time asymptotic evolution of Rayleigh-Taylor instability (RTI) is self-similar and the amplitudes of the spikes and bubbles are described by the equation hS/B = αS/B gt2, which is commonly used in various physical and engineering systems. There are significant discrepancies between theoretical, computational, and experimental calculations of αB. Experiments of uncontrolled broadband initial conditions and theoretical models of immiscible fluids yield αB~0.05, while simulations of narrowband initial conditions and miscible fluids yield αB~0.025. We present recent experiments at the National Ignition Facility, which measured the late time growth of RTI for miscible fluids (plasma state) from a well-characterized short wavelength initial perturbation. The fronts of the bubbles, the spikes and the blast wave, which initiated the instability, were each extracted from the experimental data at different times. The values of αB and αs where calculated using simulation of the 1D dynamics of the system and a Buoyancy-Drag (BD) model for the instability. |
Thursday, November 8, 2018 11:06AM - 11:18AM |
TO4.00009: Liquid Copper Rayleigh-Taylor Experiments on Omega EP Shon T. Prisbrey, James M McNaney, Channing M Huntington, Hye-Sook Park, Christopher Wehrenberg, Andrew Krygier, Edward Gumbrell Laser driven Rayleigh-Taylor experiments which utilize a releasing reservoir as a driver have been used for many years to infer the strength of solid materials, such as Ta and Pb, at multi-megabar pressures. The assumption made in the inference of strength for this platform is that the deviation of the Rayleigh-Taylor growth from the liquid solution is the measure of the strength of the material. We have designed and begun to execute an experimental campaign at the Omega EP laser facility to evaluate the growth of liquid, high density material (in this case Cu) at an unstable Rayleigh-Tayler interface. The designed loading path first shock melts the copper, then accelerates it to measure the growth of pre-imposed ripples. The goal is to demonstrate that the liquid RT growth at multi-megabar pressures can be accurately simulated. Design simulations of the experiment will be shown as well as some preliminary results from the measurements. |
Thursday, November 8, 2018 11:18AM - 11:30AM |
TO4.00010: Hydrodynamic Instabilities at an Oblique Interface Carolyn C Kuranz, Guy Malamud, Sallee Klein, Matthew Trantham, R. Paul Drake, Assaf Shimony, Alexander M Rasmus, Kirk Flippo, Carlos Di Stefano, Liam Alexis, Codie Y Fiedler Kawaguchi, Emmeline Douglas-Mann Hydrodynamic instabilities are important phenomena that occur in many high-energy-density systems, including astrophysical systems and inertial confinement fusion experiments, where pressure, density, and velocity gradients are present. Using the Omega EP laser we have created a sustained shock platform to drive a steady shock wave using a ~30 ns laser pulse. Coupled with a Spherical Crystal Imager we have created high-resolution x-ray radiographs to diagnose the evolution of complex hydrodynamic structures. This experiment involves a hydrodynamically unstable interface at an oblique angle so that the Richtmyer-Meshkov and Kelvin-Helmholtz processes are present. A precision-machined perturbation will grow due to shear and vorticity deposited at the interface. Preliminary data from recent experiments exploring the different growth between single and dual mode initial perturbations and simulations results will be shown. |
Thursday, November 8, 2018 11:30AM - 11:42AM |
TO4.00011: Shear-Driven Turbulence in High-Energy-Density Plasmas F. W. Doss, K. A. Flippo, E. C. Merritt, C. A. Di Stefano, D. W. Schmidt, J. L. Kline Shear is the original source of hydrodynamic turbulence. The plane mixing layer, in which two flowing streams drive instability and turbulence, is an extensively characterized canonical fluid dynamics reference case. Turbulent mix models derived from these canonical systems have been applied to the mixing of materials in inertial confinement fusion experiments as well as in high-energy-density (HED) instability experiments. The applicability of these models at these regimes, far from where they were derived, has an open question, with some suggestions that while residual kinetic energy resulting from large mode perturbations is likely present, turbulence may not actually be able to develop from integral driving scales due either to the short durations of the experiments or to anomalous plasma dissipation effects. Conversely, there have also been suggestions that coupling between small- and large- scale modes may enhance mixing and turbulence beyond what large-driving-mode analyses suggest. This work affirms that mixing layers consistent with classical signatures of developed turbulence can be produced in a short-lived HED plasma, and that turbulent universality apparently holds in systems 10^10 times more energetic than the systems for which these flows was originally observed. |
Thursday, November 8, 2018 11:42AM - 11:54AM |
TO4.00012: Modeling of laser-driven instability experiments Carlos Di Stefano, Alexander M Rasmus, Tiffany R Desjardins, Forrest W Doss, Kirk Flippo, Elizabeth Merritt, Brian Michael Haines, Paul A Bradley, John L Kline, Jon S Zingale We discuss the modeling of laser-driven hydrodynamic instability experiments, using the RAGE radiation-hydrodynamics code. A particular point of interest of these experiments is the effect of the laser pulse on the time-dependent shock conditions, leading to different physical processes being responsible for unstable growth. Correctly understanding the behavior of these experiments requires an understanding of these evolving conditions, and use of a laser model greatly improves our ability to model the experiments. |
Thursday, November 8, 2018 11:54AM - 12:06PM |
TO4.00013: Simulation studies of laser-irradiated additive-manufactured foams Jose L Milovich, Ogden S Jones, Mikhail Belyaev, Richard L Berger, Philip A Sterne, Scott Wilks, Benjamin J Winjum, Steven H Langer, Juergen Biener, Michael Stadermann In the indirect drive approach to inertial confinement fusion a low-Z shell containing DT fuel is compressed by x-rays produced by a laser-heated high-Z surrounding enclosure (hohlraum). The motion of the hohlraum walls introduces drive symmetry swings that may degrade the capsule performance. In low-density gas-filled hohlraums (currently the focus of ignition experiments), wall motion may completely or partially inhibit the propagation of the laser beams, especially those depositing the energy at the mid-plane of the hohlraum. To mitigate this behavior new hohlraum designs are using low-density foams as a substitute for high-density gas fills. However, standard modelling of foams has shown significant disagreement with experimental observations [1]. We show that using modern computer architectures (multi-processors) coupled to a simple statistical representation of a foam goes a long way to bridging the modelling disparities. Additional benefit can be leveraged from the use of structured foams produced by additive manufacturing (AM). We survey a variety of AM foam configurations to find an optimal design for hohlraum experiments. [1] S.Y. Gus’kov et al., Quantum Electron., 24 696 (1997). |
Thursday, November 8, 2018 12:06PM - 12:18PM |
TO4.00014: Multi-frame synchrotron based radiography of instability growth in pulsed power driven HEDP experiments Simon N Bland, David Yanuka, Alexander Rososhek, Savva Theocharous, Yakov Krasik, Jeremy Chittenden, Kristopher McGlinchey, Margie Olbinado, Alexander Rack We present the first use of multi-frame radiography from a high intensity synchrotron source to analyse the pulsed power driven explosion of wires placed in a water bath. This has enabled detailed measurements of multiple physical features, including the development of striations in the warm, dense matter of the exploding wires and, by interacting the wires with strong shock waves, detailed measurements of the growth of Richmeyer Meshkov instabilities. Experiments utilised the ID19 beamline at the European Synchrotron Radiation Facility and imaged 200µm diameter aluminium and tungsten wires exploded by a compact 30kA, 500ns current source. The high coherence of the ~30KeV probing radiation enabled beam propagation phase contrast imaging to be employed, allowing shockwaves launched by the exploding wires into the water bath and details of material inside the wires to be simultaneously captured with resolutions up to 8µm. Each experiment could have up to 128 frames of data, 0.1ns in duration, separated 704ns, and in future far faster frames could be employed. |
Thursday, November 8, 2018 12:18PM - 12:30PM |
TO4.00015: Void Closure in Porous Materials Traversed by Strong Shocks Patrick Belancourt, R. Paul Drake Porous materials are widely used in high-energy-density physics (HEDP) experiments, and are also found in astrophysical systems such as asteroids. Simulations of strong shocks passing through these systems often assume that the porous material is a homogenous gas with an averaged density. Previous models of material behavior have focused on the compaction of the voids in the presence of a relatively weak shock (such as the P-α model) or for materials that are fairly low porosity (Mie-Grueisen models). Our works considers materials with high porosities, like those often used in HEDP targets, traversed by shocks that far exceed the compaction pressure for the voids. We explore when and how radiation from such shocks can heat the voids sufficiently to cause the pores to collapse prior to the arrival of the shock. Results and examples for carbon foams will be shown. |
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