Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session GO5: Hydro Instabilities I |
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Chair: Radha Bahukutumbi, University of Rochester Room: Galerie 2 |
Tuesday, October 28, 2014 9:30AM - 9:42AM |
GO5.00001: A revision to the hydrodynamic instability theory of Chandrasekhar R. Paul Drake To address waves and instabilities in systems having volumetric vorticity, one cannot use potential flow theory and must instead work from the Euler equations (for inviscid flows). The standard model, provided for example in the relevant book by Chandrasekhar, has disturbing features, one of which is that the pressure may not be continuous across an interface. This conflicts with our basic conceptual understanding of fluids and also with derivations using potential flow. Resolving the troubling issues requires that one take a different approach to the instability derivation. One way to do so will be described herein. The revised derivation reproduces the standard results for simple Kelvin Helmholtz and Rayleigh Taylor instabilities, but obtains very different results for the case of an extended shear layer. [Preview Abstract] |
Tuesday, October 28, 2014 9:42AM - 9:54AM |
GO5.00002: Hydrodynamic instabilities of finite width layers Marc Henry de Frahan, Eric Johnsen, R. Paul Drake The understanding of multi-material mixing in areas such as inertial confinement fusion and astrophysics relies on accurate characterization of fluid mixing from hydrodynamic instabilities, including the Rayleigh-Taylor, and Kelvin-Helmholtz instabilities. We investigate these instabilities by studying the problem of an extended perturbed shear layer with and without the presence of gravity. An initially perturbed fluid layer is placed in a shear flow. The velocity difference at the interfaces leads to the development of vortical structures and fluid mixing at the interfaces. The presence or absence of gravity dictates the strength of the Rayleigh-Taylor instability phase relative to the Kelvin-Helmholtz instability. Using a high-order numerical method that accurately represents material and flow discontinuities, we identify stable and unstable configurations depending on the Richardson number, and the ratios of the initial perturbation amplitude and layer thickness to the wavelength. [Preview Abstract] |
Tuesday, October 28, 2014 9:54AM - 10:06AM |
GO5.00003: Overview of the Marble experiment M.R. Douglas, J.R. Fincke, G.P. Grim, B.M. Haines, T.J. Murphy, R.E. Olson, R.C. Shah, J.M. Smidt, I.L. Tregillis, J.A. Oertel Work is underway to develop a new ICF platform on the Omega and NIF facilities to better quantify the influence of heterogeneous mix on fusion burn. Results of these experiments will be compared to a probability distribution function (PDF) burn model that has been developed to address yield from separated reactant experiments. CH capsules comprised of CH or CD solid foam cores containing tritium gas are being proposed along with capsules filled with a mixture of deuterated propane and tritium gas. For configurations in which the D and T are initially spatially separated, subsequent DT yield is used to characterize the mix. An overview of the experimental concept will be presented, and simulations in preparation for the platform will be discussed. This work is supported~by the US DOE performed by LANL under contract DE-AC52-06NA25396. [Preview Abstract] |
Tuesday, October 28, 2014 10:06AM - 10:18AM |
GO5.00004: The Marble experimental plan T.J. Murphy, M.R. Douglas, J.R. Fincke, R.D. Gilbertson, G.P. Grim, B.M. Haines, C.E. Hamilton, J.A. Oertel, R.E. Olson, D.W. Schmidt, R.C. Shah, J.M. Smidt, I.L. Tregillis The Marble campaign will quantify the effects of heterogeneous mix on fusion burn in ICF capsules using deuterated foam and tritium gas filled capsules. The heterogeneousness of the mix will be controlled by varying the porosity of the foam. Platform development efforts are underway, and experiments will be performed in FY2015 on Omega using direct-drive capsule implosions and on NIF using near-vacuum hohlraum capsule implosions to provide initial data on the performance of foam-filled capsule implosions. Capsules filled with a mixture of deuterated propane and tritium will be used as controls, providing data from uniformly mixed reactants. Capsules filled with engineered foams of specified porosity are currently being developed. [Preview Abstract] |
Tuesday, October 28, 2014 10:18AM - 10:30AM |
GO5.00005: Bubble Acceleration in the Three-Dimensional Ablative Rayleigh--Taylor Instability R. Yan, R. Betti In inertial confinement fusion, the growth of the Rayleigh--Taylor instability (RTI) at the ablation front causes a severe degradation in implosion performance by reducing the hot-spot pressure, temperature, and density. During the linear phase, the RTI growth is mitigated by mass ablation. However, during the nonlinear phase, mass ablation can be destabilizing. The ablative RTI is investigated in 3-D geometry using our newly developed code \textit{ART3D}. It is found that mass ablation causes an accumulation of vorticity inside the bubble in the nonlinear regime. The vorticity-acceleration mechanism drives the bubble velocity faster than in the classical RTI for a 2-D geometry.\footnote{R. Betti and J. Sanz, Phys. Rev. Lett. \textbf{97}, 205002 (2006).} \textit{ART3D} simulations indicate that the 3-D bubble velocity increases monotonically to values faster than in 2-D without reaching an asymptotic speed in deuterium and tritium shells. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786. [Preview Abstract] |
Tuesday, October 28, 2014 10:30AM - 10:42AM |
GO5.00006: Hydrodynamic Scaling of the Deceleration-Phase Rayleigh--Taylor Instability for Inertial Confinement Fusion Implosions A. Bose, R. Betti, K. Woo, R. Nora Hydrodynamic equivalence and ignition theory allow for the extrapolation of OMEGA experiments to ignition-scale implosions. The yield-over-clean (YOC $=$ measured yield/1-D yield) depicts the effect of hydro-instabilities on inertial confinement fusion implosions. A 2-D study of the deceleration-phase Rayleigh--Taylor instability (RTI) is carried out to assess the YOC scaling with target size at varying nonuniformity levels. The deceleration-phase ablative RTI is mitigated by the hot-spot thermal and radiation transport, which do not scale hydro-equivalently. Scaling of the thermal conduction shows that hot-spot ablation velocity is higher on OMEGA than on the National Ignition Facility (NIF), resulting in higher RTI growth factors on the NIF. Radiation emitted in the hot-spot makes the implosion nearly hydro-equivalent by increasing the density gradient scale length on the NIF. Thermal conduction and radiation both are nonscalable physics in the deceleration phase, with complementary impacts the scaling of deceleration-phase RTI. Analytic and numerical study of the deceleration-phase RTI on OMEGA and NIF-scale targets show that YOC$_{\mathrm{NIF}}$ $\sim$ YOC$_{\Omega}$ considering identical laser imprinting and normalized ice roughness levels. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786. [Preview Abstract] |
Tuesday, October 28, 2014 10:42AM - 10:54AM |
GO5.00007: Results from directly driven implosions of deuterated plastic shells filled with tritium gas Gary Grim, Daniel Casey, Jim Fincke, Jesse Pino, Vladimir Smalyuk, Mike Steinkamp, Robert Tipton Results from implosions of tritium filled plastic shells containing thin deuterated sub-layers, as well as comparisons with 1-D capsule only simulations will be reported. The implosions were directly driven using a square, 1 ns wide, 27 kJ laser pulse, provided by the Laboratory for Laser Energetics, University of Rochester, Rochester, NY. The 15 um thick, by 865 $\mu$m OD, CH capsules were fabricated with 1 $\mu$m thick, deuterated plastic layers, located either in direct contact with the tritium gas, or offset by a layer of CH. Neutrons produced by deuterium-tritium fusions signify atomic mixing between the deuterated shell and the gas payload, allowing for a detailed study of the dynamics of mix in 3-D implosions. Data has been collected on implosions from capsules with a depth of burial of 0, 1, and 2 um of CH, as well as non-deuterated control shots. Capsules were shot with two gas fill pressures, 4 and 10 atm., to provide information on mix as a function of convergence. We report nuclear and X-ray data collected from these experiments. Further, we present comparisons with, 1-D and 2-D, capsule only simulations. [Preview Abstract] |
Tuesday, October 28, 2014 10:54AM - 11:06AM |
GO5.00008: Fuel Cavity Asymmetry at the Onset of Deceleration in ICF Rahul C. Shah, F.J. Wysocki, V. Glebov, P. Hakel, T. Joshi, G. Kagan, R.C. Mancini, T.J. Murphy, C. Stoeckl, B. Yaakobi, J.F. Benage In ICF, the impact on symmetry of low mode drive non-uniformity is amplified by high convergence. Measurements have shown low mode areal density variation [1], however, direct impact of low modes on fuel volume has remained undemonstrated. We suggest our images provide first evidence of symmetry loss at the fuel-shell interface. The experiments use direct-drive spherical implosions (Omega). The inner 100 nm layer of the plastic shell is doped with diagnostic Ti to obtain information about interface position, temperature and density. Measurement is made at onset of deceleration at which time nuclear yield rate (NTD) and time resolved (SSCA) spectrum both are in agreement with 1-D prediction. Spectrally resolved images are obtained using the Multiple Monochromatic Imager, which combines a pinhole array with x-ray dispersive mirror and gated detector [2]. Angle averaging of the limb-brightened image data also shows agreement with the 1D calculation. However, the 2D image shows $\sim$ 20{\%} brightness variations over modes 2-10. These modulations are discussed in context of predicted variations of interface position.\\[4pt] [1] C.K. Li \textit{et.al.} PRL \textbf{92}: 205001 (2004).\\[0pt] [2] T.Nagayama \textit{et.al.} J. Appl. Phys. \textbf{109}: 093303 (2011). [Preview Abstract] |
Tuesday, October 28, 2014 11:06AM - 11:18AM |
GO5.00009: Results of a supersonic, single-mode, shockwave-driven Kelvin-Helmholtz instability experiment W.C. Wan, G. Malamud, C.A. Di Stefano, M.R. Trantham, S.R. Klein, A. Shimony, D. Shvarts, C.C. Kuranz, R.P. Drake The Kelvin-Helmholtz instability is a hydrodynamic process that causes mixing at an interface with shear flow. It is prevalent in many high-energy-density systems such as fusion research, core-collapse supernovae, and protoplanetary disks. Although it is common to simplify the Euler equations by assuming incompressibility, this assumption does not account for the inhibited growth rate found in supersonic flows. Here, we present the first laboratory observations of single-mode, compressible Kelvin-Helmholtz instability growth. This experiment was performed at the OMEGA-EP facility using three beams stitched into a 28 ns square pulse to sustain a shockwave in low-density foam. The shockwave generated shear along the interface between the foam and a high-density plastic, seeded with a precisely machined single-mode sinusoidal perturbation. The system was diagnosed using radiography with a spherically bent crystal. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840, the National Laser User Facility Program, grant number DE-NA0000850, and the Laboratory for Laser Energetics, University of Rochester by the NNSA/OICF under Cooperative Agreement No. DE-FC52-08NA28302 [Preview Abstract] |
Tuesday, October 28, 2014 11:18AM - 11:30AM |
GO5.00010: Oblique Shock Experiments on the OMEGA-EP Laser Jonathan Hager, Kirk Flippo, Forrest Doss, John Kline, Wesley Wan, Carlos Di Stefano, Carolyn Kuranz, Paul Drake In inertial confinement fusion (ICF), understanding the evolution of hydrodynamic instability growth is an essential part of designing an implosion target that is robust to mix between the cold target shell and the hot fusion core. Early in time, shocks traversing the target amplify seed modulations through the slow growing Richtmyer-Meshkov (RM) and Kelvin-Helmholtz (KH) instabilities. These instabilities seed the faster growing Rayleigh-Taylor (RT) instability during the acceleration and deceleration phases of the implosion. We present an experimental platform designed to investigate coupling between the RM and KH instabilities by launching a planar shock through a polyamide-imide cylinder on the OMEGA-EP laser. The rear surface of the target has a single mode sinusoidal seed modulation that is machined on an interface that is at an angle with respect to the planar shock, creating an oblique shock breakout. The evolution of the rear surface modulation is measured using side-on x-ray radiography with a spherical crystal imager backlight by a copper k-alpha source. Experimental data will be presented along with comparisons with 1-D and 2-D simulation predictions. [Preview Abstract] |
Tuesday, October 28, 2014 11:30AM - 11:42AM |
GO5.00011: Effects of Self-Generated Magnetic Fields in Rayleigh--Taylor Unstable Laser-Irradiated Plastic Foils I.V. Igumenshchev Self-generated magnetic fields during the nonlinear Rayleigh--Taylor (RT) growth in laser-driven plastic foils are studied using 2-D magnetohydrodynamic simulations. The simulations show that at intensities of $\sim 6 \times 10^{14}$ W/cm$^{2}$, the dynamics of the fields sourced by the Biermann battery effect ($\sim \nabla T_{\mbox{e}} \times \nabla n_{\mbox{e}}$) are strongly affected by the Nernst convection, which compresses the fields toward the ablation surface. As a result, the fields are localized in areas of high resistivity and related magnetic dissipations limit the field growth, determining the magnitude of the fields. The fields saturate at about 2 to 3 MG for perturbation wavelengths $L > 100$ $\mu$m and at less than 0.1 MG for $L < 10$ $\mu$m because of increased magnetic dissipations at small spatial scales. Self-generated fields can moderately affect the nonlinear RT growth by redistributing heat fluxes for perturbations with $L > 100$ $\mu$m. The simulations show good agreement with measurements of magnetic fields in recent direct-drive planar experiments on the OMEGA EP laser.\footnote{L. Gao \textit{et al.}, Phys. Rev. Lett. \textbf{109}, 115001 (2012). } This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Tuesday, October 28, 2014 11:42AM - 11:54AM |
GO5.00012: Significant reduction of instability growth in magnetically driven liner implosions Kyle Peterson, Tom Awe, Steve Rosenthal, Ryan McBride, Daniel Sinars, Edmund Yu, Grafton Robertson, Mike Cuneo, Mark Savage, Patrick Knapp, Paul Schmit, Steve Slutz, Brent Blue, Diana Schroen, Kurt Tomlinson Recent experiments on Sandia's Z facility have shown a significant reduction of instability growth [1] in solid metallic rods driven with a $\sim$20 MA, 100ns current pulse when thick, $\sim$70 $\mu$m dielectric coatings were employed to mitigate nonlinear growth of the electrothermal instability [2]. In this paper, we present new electrothermal mitigation experiments with MagLIF [3] relevant aluminum (aspect ratio 9) and beryllium liners (aspect ratio 6). These experiments show a similar improvement in instability performance while imploding to much higher convergence ratios and undergoing much greater acceleration.\\[4pt] [1] K.J. Peterson, T. J. Awe, et al., PRL 112, 135002 (2014).\\[0pt] [2] K.J. Peterson, D. B. Sinars, et al., Phys. Plasmas 20, 056305 (2012).\\[0pt] [3] S.A. Slutz et al., Phys. Plasmas 17, 056303 (2010). [Preview Abstract] |
Tuesday, October 28, 2014 11:54AM - 12:06PM |
GO5.00013: EEffect of initial amplitude onon the interfacial and bulk dynamics in Richtmyer-Meshkov iInstability under conditions of high energy density Zachary R. Dell, Robert F. Stellingwerf, Snezhana I. Abarzhi We systematically study the effect of the initial amplitude on the inter-facial and bulk dynamics of the Richtmyer-Meshkov instability (RMI) induced by strong shocks. The shock propagates from the light to the heavy fluid. The fluid densities are contrast. The fluid interface is initially perturbed with a cosine wave perturbation. Its amplitude is varied from 0\% to 100\% of the initial perturbation wavelength. A broad range of the shock strengths and density ratios is considered. Smoothed particle hydrodynamics code is employed to ensure shock capturing and interface tracking. Detailed diagnostics of the flow scalar and vector fields is performed. Whenever possible the simulation results are compared with existing theoretical analyses achieving good agreement. The focus question of our study is how the energy deposited by the shock is partitioned between the inter-facial and volumetric components. We analyze the dependence of the initial growth-rate of RMI, the velocity away from the interface, and the transmitted shock velocity as functions of the initial amplitude. Particularly, we found that for a Mach number 5 and an Atwood number 0.8, the initial growth rate is highest and the inter-facial energy is the largest when the initial amplitude is about a quarter of the wavelength. [Preview Abstract] |
Tuesday, October 28, 2014 12:06PM - 12:18PM |
GO5.00014: Accelerated dynamics of blast wave driven Rayleigh-Taylor instabilities in high energy density plasmas N. Swisher, C. Kuranz, R.P. Drake, S.I. Abarzhi We report the systematic analysis of experimental data describing the late time evolution of the high Mach number and high Reynolds number Rayleigh-Taylor instability which is driven by a blast wave. The parameter regime is relevant to high energy density plasmas and astrophysics. The experiments have been conducted at the Omega laser facility. By processing the experimental x-ray images, we quantified the delicate features of RT dynamics, including the measurements of the curvature of the transmitted shock and the interface envelopes, the positions of RT bubbles and spikes, and the quantification of statistics of RT mixing. The measurements were performed at four time steps and for three different initial perturbations of the target (single mode and two two-mode). We found that within the noise level the curvatures of the shock and interface envelope evolve steadily and are an imprint of laser imperfections. At late times, the bubble merge does not occur, and the flow keeps significant degree of order. Yet, the blast-wave-driven RT spikes do accelerate with the power-law exponent smaller than that in case of sustained acceleration. We compared the experimental results with the momentum model of RT mixing and stochastic model achieving good agreement. [Preview Abstract] |
Tuesday, October 28, 2014 12:18PM - 12:30PM |
GO5.00015: Stability of a hydrodynamic discontinuity Snezhana I. Abarzhi, Yasuhide Fukumoto, Leo P. Kadanoff While looking from a far field at a discontinuous front separating two incompressible ideal fluids of different densities, we identify two qualitatively different behaviors of the front (unstable and stable) depending upon whether the energy flux produced by the perturbed front is large or small compared to the flux of kinetic energy across the planar front. Landau's solution for the Landau-Darrieus instability is consistent with one of these cases, whether the gravity is present or not. [Preview Abstract] |
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