Bulletin of the American Physical Society
58th Annual Meeting of the APS Division of Plasma Physics
Volume 61, Number 18
Monday–Friday, October 31–November 4 2016; San Jose, California
Session GO8: HED Hydrodynamics and Shocks |
Hide Abstracts |
Chair: Elizabeth Merritt, Los Alamos National Laboratory Room: 212 CD |
Tuesday, November 1, 2016 9:30AM - 9:42AM |
GO8.00001: Hydrodynamic Instabilities at an Oblique Interface in the light to heavy configuration Carolyn Kuranz, G. Malamud, S.R. Klein, M Trantham, R.P. Drake, D. Shvarts, W.C. Wan, A.M. Rasmus, K. Flippo, J Kline, C.A. Di Stefano, A. Shimony 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 \textasciitilde 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. This work is supported by the U.S. DOE, through NNSA grants\textunderscore DE-NA0002956 (SSAA) and DE-NA0002719 (NLUF), by the LLE under DE-NA0001944, and by the LLNL under subcontract B614207 to DE-AC52-07NA27344 and by LANL under subcontract BA154750/SC343761. [Preview Abstract] |
Tuesday, November 1, 2016 9:42AM - 9:54AM |
GO8.00002: Coupled hydrodynamic instability growth on oblique interfaces in a heavy to light configuration A.M. Rasmus, K.A. Flippo, C.A. Di Stefano, F.W. Doss, E.C. Merritt, T. Cardenas, D.W. Schmidt, J.L. Kline, C.C. Kuranz Hydrodynamic instabilities play an important role in the evolution of inertial confinement fusion and astrophysical phenomena. Three of the Omega-EP long pulse beams (10 ns square pulse, $\sim$14 kJ total energy, 1.1 mm spot size) drive a supported shock across a heavy-to-light, oblique, interface. Simple, single-mode, and more complex, double and multi-mode, initial conditions seed coupled Richtmeyer-Meshkov (RM), Rayleigh-Taylor (RT), and Kelvin-Helmholtz (KH) growth. The obliqueness of the interface is varied to alter the relative importance of KH to RM and RT. The Spherical Crystal Imager is used to take high resolution x-ray radiographs of the interface as it evolves. The results of single and double-mode experiments along with simulations using the multi-physics hydro-code RAGE will be presented. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0002956. This work performed under the auspices of the U.S. Department of Energy by LANL under contract DE-AC52-06NA25396. This material is partially supported by DOE Office of Science Graduate Student Research (SCGSR) program. [Preview Abstract] |
Tuesday, November 1, 2016 9:54AM - 10:06AM |
GO8.00003: High-Energy-Density Shear Flow and Instability Experiments F. W. Doss, K. A. Flippo, E. C. Merritt, C. A. Di Stefano, B. G. DeVolder, S. Kurien, J. L. Kline High-energy-density shear experiments have been performed by LANL at the OMEGA Laser Facility and National Ignition Facility (NIF). The experiments have been simulated using the LANL radiation-hydrocode RAGE and have been used to assess turbulence models’ ability to function in the high-energy-density, inertial-fusion-relevant regime. Beginning with the basic configuration of two counter-oriented shock-driven flows of $>$ 100~km/s, which initiate a strong shear instability across an initially solid-density, 20~$\mu$m thick Al plate, variations of the experiment to details of the initial conditions have been performed. These variations have included increasing the fluid densities (by modifying the plate material from Al to Ti and Cu), imposing sinusoidal seed perturbations on the plate, and directly modifying the plate's intrinsic surface roughness. Radiography of the unseeded layer has revealed the presence of emergent Kelvin-Helmholtz structures which may be analyzed to infer fluid-mechanical properties including turbulent energy density. [Preview Abstract] |
Tuesday, November 1, 2016 10:06AM - 10:18AM |
GO8.00004: The NIF Shear Experiment: Emergent Coherent Structures and Initial Conditions K. A. Flippo, F. W. Doss, E. C. Merritt, C. A. Di Stefano, B. G. DeVolder, S. Kurien, L. Kot, E. N. Loomis, T. J. Murphy, T. S. Perry, J. L. Kline, C. M. Huntington, S. R. Nagel, S. A. MacLaren, D. W. Schmidt The NIF Shear experiments are designed to stress turbulence models at high Atwood numbers, high convective Mach number, and in a highly compressible regime. The NIF laser system is used to drive two hohlraums on either end of the experiment, which convert the laser drive into a bath of soft x-rays, 250eV in temperature. The counter-propagating shocks and flow, pressure balance the shear layer, such that it can grow due to the KH instability in the center of the experiment for 20 ns. These experiments are the first High Energy Density (HED) hydro-instability studies to show emergent coherent Kelvin-Helmholtz (KH) structures arising from random broadband seeds, and the first to control the phenomenological evolution of the tracer layer by controlling the initial surface roughness conditions. The change in initial conditions forces the system evolution on a different path that does not appear to reach a universal nor self-similar state by the end of the experiment. The experiment was modeled using the multi-physics hydrodynamic code RAGE with the BHR turbulence model. The initial scale-length of the model is modified to match the data. When the model is turned off, the pure hydrodynamics do not capture the behavior of the mixing layer and cannot match the data. [Preview Abstract] |
Tuesday, November 1, 2016 10:18AM - 10:30AM |
GO8.00005: The effects of sinusoidal initial conditions on finite-thickness, HED shear flows Carlos Di Stefano, Elizabeth Merritt, Forrest Doss, Tiffany Desjardins, Kirk Flippo, John Kline, Eric Loomis, Alex Rasmus Hydrodynamic shear instability plays a role in any system in which shear flow across materials can be found, including in high-energy-density examples such as fusion plasmas and many astrophysical systems. In this work we describe experiments, performed on the OMEGA laser, exploring shear instability through the use of carefully-controlled, single-mode initial conditions. A novel aspect of these experiments is that they employ counter-propagating shocks separated by a collimating layer. This produces a region of shear flow in which the pressure is balanced across flow, simplifying theoretical analysis and modeling. We discuss two interesting behaviors seen in these experiments. First, at early times, radiographs show the expansion of the collimator and the spectral evolution of the initial perturbation features from laser-drive heating of the material. The evolved features then couple to the primary shear instability we seek to probe. Second, at late times, we observe the persistence of a coherent long-wavelength mode in the mixing layer, driven by the imposed surface perturbation, which resonates with and the length scale introduced by the finite thickness of the collimator. [Preview Abstract] |
Tuesday, November 1, 2016 10:30AM - 10:42AM |
GO8.00006: Preliminary results of the redesigned Reshock experiment at the OMEGA laser facility Tiffany Desjardins, Carlos Di Stefano, Elizabeth Merritt, Forrest Doss, Kirk Flippo, John Kline The redesigned LANL OMEGA \textit{Reshock} campaign is exploring the effects of turbulent mixing due to the Richtmyer-Meshkov (RM) instability as part of an ongoing effort to assess the LANL radiation-hydrocode the BHR mix model in the high-energy density regime. Platform improvements have been made to increase the precision of the instability growth measurements. The experiments are conducted in similar geometry to the previous \textit{Reshock} campaigns. A cylindrical beryllium tube is filled with a low-density CH-foam ($\rho \approx $100-150 mg/cc) and a higher density tracer layer that is displaced from an endcap. Two tracer materials have been tested: a low-density plastic ($\rho _{\mathrm{0}}=$1.5 g/cc) layer 40\textmu m thick, and an HDC layer ($\rho_{\mathrm{0}}=$3.2 g/cc) 15 \textmu m thick. The tracer layers have been $\rho $r matched to the previously used aluminum tracer ($\rho _{\mathrm{0}}=$2.43 g/cc). In this platform two shockwaves are generated from opposite ends of the shock tube by a $\approx $5 kJ laser pulse, with time delay $\Delta $t$\approx $3-6ns between them. The primary shockwave generates the initial mixing between the tracer layer and surrounding foam. The second shock leads to a compression of the initial mix layer and to increased turbulence. We will present both initial design simulations for shock timing and tracer choice and preliminary data from the first shot day. [Preview Abstract] |
Tuesday, November 1, 2016 10:42AM - 10:54AM |
GO8.00007: Shock-driven Rayleigh-Taylor/Richtmyer-Meshkov ripple evolution measurements using the split target geometry S. R. Nagel, C. M. Huntington, S. A. Maclaren, K. S. Raman, T. Baumann, J. Bender, L. R. Benedetti, J. P. Holder, L. Savage, R. M. Seugling, L. Simmons, P. Wang, K. A. Flippo, T. S. Perry The study of singly or multiply shocked Rayleigh-Taylor/Richtmyer-Meshkov systems usually uses an opaque, denser material to track the perturbed interface that is driven into a lower density, more transparent material. A difficulty of this setup is the obscuration of small-scale features, especially of the lighter material by the opaque denser material, can change the mix-width measurement. To mitigate this, we use a split target where one half produces a conventional radiograph, while the other provides an inverse image, where the light material is opaque and the dense material is transparent. \\ Here we present first measurements from re-shock experiments at the NIF, which use such a split target geometry to investigate the mix-width for initial single mode and 2D multimode perturbations. [Preview Abstract] |
Tuesday, November 1, 2016 10:54AM - 11:06AM |
GO8.00008: Three- and Two- Dimensional Simulations of Re-shock Experiments at High Energy Densities at the National Ignition Facility Ping wang, Kumar Raman, Stephan MacLaren, Channing Huntington, Sabrina Nagel We present simulations of recent high-energy-density (HED) re-shock experiments on the National Ignition Facility (NIF). The experiments study the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instability growth that occurs after successive shocks transit a sinusoidally-perturbed interface between materials of different densities. The shock tube is driven at one or both ends using indirect-drive laser cavities or hohlraums. X-ray area-backlit imaging is used to visualize the growth at different times. Our simulations are done with the three-dimensional, radiation hydrodynamics code ARES, developed at LLNL. We show the instabilitygrowth rate, inferred from the experimental radiographs, agrees well with our 2D and 3D simulations. We also discuss some 3D geometrical effects, suggested by our simulations, which could deteriorate the images at late times, unless properly accounted for in the experiment design. [Preview Abstract] |
Tuesday, November 1, 2016 11:06AM - 11:18AM |
GO8.00009: Fully-kinetic simulations of the Rayleigh-Taylor instability in high-energy-density plasmas E. Paulo Alves, Warren B. Mori, Frederico Fiuza The Rayleigh-Taylor instability (RTI) in high-energy-density (HED) plasmas is a central problem in a wide range of scenarios. It dictates, for instance, the dynamics of supernovae in astrophysical plasmas, and is also recognized as a critical challenge to achieving ignition in inertial confinement fusion. In some of these conditions the Larmor radius or Coulomb mean free path (m.f.p.) is finite, allowing kinetic effects to become important, and it is not fully clear how the development of the RTI deviates from standard hydrodynamic behavior. In order to obtain an accurate description of the RTI in these HED conditions it is essential to capture the self-consistent interplay between collisional and collisionless plasma processes, and the role of self-generated electric and magnetic fields. We have explored the dynamics of the RTI in HED plasma conditions using first-principles particle-in-cell simulations combined with Monte Carlo binary collisions. Our simulations capture the role of kinetic diffusion as well as the self-generated electric (e.g. space-charge) and magnetic (e.g. Biermann battery) fields on the growth rate and nonlinear evolution of the RTI for different plasma conditions. We will discuss how different collisional m.f.p. relative to the collisionless plasma skin depth affect the RTI development. [Preview Abstract] |
Tuesday, November 1, 2016 11:18AM - 11:30AM |
GO8.00010: Shock front field structure~in low-density systems Rui Hua, Christopher Mucguffey, Farhat Beg, Hong Sio, Yuan Ping, Scott Wilks, Bob Heeter, Rip Collins It is known that a shock front is not a simple discontinuity in density and temperature as depicted in commonly used hydro codes but also consists of self-generated fields associated with gradients in the electron pressure. A quasi-planar platform using broadband proton radiography has been developed to study this field structure at a shock front. The broad bandwidth offers energy-dependent measurements which quantitatively constrain both the potential and field width at the shock front. Experiments were conducted on the OMEGA EP, where three long pulse beams delivered 6 kJ in 2 ns for shock initiation in a tube filled with either pure Helium or mixture of Helium and Neon, and a short pulse of 850 J, 10 ps generated broadband protons for point-projection radiography. Simultaneous spatially resolved soft-x-ray spectroscopy provided shock velocity, particle velocity and thermal emission measurements, constraining density and temperature for the field generation. The data and modeling indicate that a multi-KeV potential was present at the shock front where a strong electron pressure gradient existed.~ [Preview Abstract] |
Tuesday, November 1, 2016 11:30AM - 11:42AM |
GO8.00011: Counter-propagating radiative shock experiments on the Orion laser facility T. Clayson, F. Suzuki-Vidal, S.V. Lebedev, G.F. Swadling, G.C. Burdiak, S. Patankar, R.A. Smith, J. Foster, J. Skidmore, E. Gumbrell, P. Graham, C. Danson, C. Stehlé, R.L. Singh, U. Chaulagain, J. Larour, M. Kozlova, C. Spindloe The Orion high-power laser facility, at AWE Aldermaston UK, was used to produce hyper-sonic radiative shocks, travelling at ~60km/s, in noble gases, between 0.1 and 1.0 bar. These experiments aimed to study the radiative precursor, a heat and ionization wave preceding the shock front, and dynamics of colliding radiative shocks. X-ray backlighting and optical self-emission streak imaging were used to study the shock front and collision dynamics, while multi-frame and streaked interferometry were used to simultaneously study the radiative precursor. These experiments compared the shock and collision dynamics in different gases (e.g. Ne, Ar, Kr, Xe), while maintaining a constant mass density, to vary the strength of the radiative precursor. Some shocks exhibited features suggesting the formation of hydrodynamic or radiative instabilities. The experimental data is in good agreement with 2-D rad-hydro simulations and provides a new benchmark for codes to be tested against. [Preview Abstract] |
Tuesday, November 1, 2016 11:42AM - 11:54AM |
GO8.00012: Generation of Gigabar Pressures for High-Energy-Density Plasmas W. Theobald, R. Betti, A. Bose, W. Seka, C. Stoeckl, D. Mangino, A. Casner, F.N. Beg, E. Llor Aisa, X. Ribeyre, M.S. Wei, M.E. Schoff, R. Florido, R.C. Mancini Experiments on the OMEGA laser were performed to study gigabar pressures in small (50-$\mu $m-diam) Ti and Cu target samples for high-energy-density plasma applications. The samples were precisely placed (better than 10 $\mu $m) at the center of a spherical plastic matrix that is irradiated at incident laser intensities of $\sim 5\mbox{\thinspace }\times \mbox{\thinspace }10^{15}\mbox{\thinspace }{\mbox{W}} \mathord{\left/ {\vphantom {{\mbox{W}} {\mbox{cm}^{2}}}} \right. \kern-\nulldelimiterspace} {\mbox{cm}^{2}}.$ The laser launches a spherical shock wave that converges in the center in order to reach Gbar pressures in the sample. The shock convergence produces a short burst $\left( {\sim 30\mbox{\thinspace ps}} \right)$ of x-ray emission. Time-resolved and time-integrated x-ray spectroscopy provides the means to diagnose the plasma conditions in the sample. The time-resolved spectra are compared to predictions from radiation--hydrodynamic simulations to infer the material conditions at Gbar pressures. A second x-ray flash delayed by $\sim 600\mbox{\thinspace ps}$ caused by the breakout of the rebounded shock through the outer surface of the compressed plastic was observed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by the Fusion Science Center under Grant No. DE-FC02-04ER54789. [Preview Abstract] |
Tuesday, November 1, 2016 11:54AM - 12:06PM |
GO8.00013: Absolute Hugoniot measurements for CH foams in the 1.5-8 Mbar range Y. Aglitskiy, A.L. Velikovich, A. J. Schmitt, M. Karasik, V. Serlin, J.L. Weaver, J. Oh, S.P. Obenschain We report the absolute Hugoniot measurements for dry CH foams at 10{\%} of solid polystyrene density. The 400 $\mu $m thick, 500 $\mu $m wide planar foam slabs covered with a 10 $\mu $m solid plastic ablator were driven with 4 ns long Nike KrF laser pulses whose intensity was varied between 10 and 50 TW/cm$^{\mathrm{2}}$. The trajectories of the shock front and the ablative piston, as well as the rarefaction fan emerging after the shock breakout from the rear surface of the target were clearly observed using the side-on monochromatic x-ray imaging radiography. From these measurements the shock density compression ratio and the shock pressure are evaluated directly. The observed compression ratios varied between 4 and 8, and the corresponding shock pressures -- between 1.5 and 8 Mbar. The data was simulated with the FASTRAD3D hydrocode, using standard models of inverse bremsstrahlung absorption, flux-limited thermal conduction, and multi-group radiation diffusion. The demonstrated diagnostics technique applied in a cryo experiment would make it possible to make the first absolute Hugoniot measurements for liquid deuterium or DT-wetted CH foams, which is relevant for designing the wetted-foam indirect-drive ignition targets for NIF. [Preview Abstract] |
Tuesday, November 1, 2016 12:06PM - 12:18PM |
GO8.00014: Shock induced cavity collapse. Jonathan Skidmore, Hugo Doyle, Brett Tully, Matthew Betney, Peta Foster, Tim Ringrose, Rohan Ramasamy, James Parkin, Tom Edwards, Nicholas Hawker . Results from the experimental investigation of cavity collapse driven by a strong planar shock (\textgreater 6km/s) are presented. Data from high speed framing cameras, laser backlit diagnostics and time-resolved pyromety are used to validate the results of hydrodynamic front-tracking simulations. As a code validation exercise, a 2-stage light gas gun was used to accelerate a 1g Polycarbonate projectile to velocities exceeding 6km/s; impact with a PMMA target containing a gas filled void results in the formation of a strong shockwave with pressures exceeding 1Mbar. The subsequent phenomena associated with the collapse of the void and excitation of the inert gas fill are recorded and compared to simulated data. Variation of the mass density and atomic number of the gas fill is used to alter the plasma parameters furthering the extent of the code validation. [Preview Abstract] |
Tuesday, November 1, 2016 12:18PM - 12:30PM |
GO8.00015: Evolution of shock through a void in foam Y. Kim, J. M. Smidt, T. J. Murphy, M. R. Douglass, B. G. DeVolder, J. R. Fincke, D. W. Schmidt, T. Cardenas, S. G. Newman, C. E. Hamilton, T. J. Sedillo Marble implosion is an experimental campaign intended to study the effects of heterogeneous mix on fusion burn. A spherical capsule is composed of deuterated plastic foam of controlled pore (or void) size with tritium fill in pores. As capsule implosion evolves, the initially separated deuterium and tritium will mix, producing DT yields. Void evolution during implosion is of interest for the Marble campaign. A shock tube, driven by the laser at Omega, was designed to study the evolution of a shock through a foam-filled ``void'' and subsequent void evolution. Targets were comprised of a 100 mg/cc CH foam tube containing a 200-\textmu m diameter, lower density doped foam sphere. High-quality, radiographic images were obtained from both 2{\%} iodine-doped in plastic foam and 15{\%} tin-doped in aerogel foam. These experiments will be used to inform simulations. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700