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 JO04: ICF: Hydrodynamic Instabilities and MixOn Demand
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Chair: David Meyerhofer, Los Alamos National Laboratory Room: Rooms 304-305 |
Tuesday, November 9, 2021 2:00PM - 2:12PM |
JO04.00001: D'yakov-Kontorovich instability of expanding shock waves Alexander L Velikovich, César Huete The D’yakov-Kontorovich (DK) instability of a steady planar shock front theoretically discovered in the 1950s is the hardest-to-detect and the least understood among the hydrodynamic instabilities. At certain combinations of the EoS and shock-loading conditions, non-decaying oscillations of an isolated shock front are generated, accompanied by a spontaneous acoustic emission (SAE). We report an analytical study of the DK instability for spherical and cylindrical steadily expanding accretion shock waves. The acoustic feedback from the center or axis of symmetry changes the perturbation dynamics entirely compared to the classical isolated-shock case. When the DK instability emission conditions are satisfied, shock-front perturbations grow as a power of time. Shock divergence is a stabilizing factor: only high modes are unstable. In Bates and Montgomery’s example for a van der Waals fluid, cylindrical and spherical expanding shocks become unstable at mode numbers m>148 and l>213, respectively. Our analytical results constitute a challenging verification test for hydrocodes used in inertial confinement fusion. |
Tuesday, November 9, 2021 2:12PM - 2:24PM |
JO04.00002: Energy transfer across scales in Rayleigh-Taylor flows Hussein Aluie, Dongxiao Zhao, Riccardo Betti We identify two main processes for energy transfer across scales in Rayleigh-Taylor (RT) flows: baropycnal work Λ, due to pressure gradients, and deformation work π, due to flow strain. We show how these fluxes exhibit a quadratic-in-time self-similar evolution similar to RT mixing layer. Λ is a conduit for potential energy, transferring energy non-locally from the largest scales to smaller scales where π takes over. In 3D, π continues a persistent cascade to yet smaller scales, whereas in 2D, π re-channels the energy back to larger scales. This gives rise to a positive feedback loop in 2D-RT (absent in 3D) in which mixing layer growth and the associated potential energy release are enhanced relative to 3D, yielding the well-known larger α values in 2D simulations. Despite higher bulk kinetic energy levels in 2D, small scales are weaker than in 3D. We also find that net upscale cascade in 2D tends to isotropize the large-scale flow, in stark contrast to 3D-RT. These fundamental differences pinpoint the misleading physics inherent to 2D-RT simulations in ICF modeling. Our findings also indicate the absence of net upscale energy transfer in 3D-RT as is often claimed; growth of large-scale bubbles and spikes is not due to "mergers" but solely due to baropycnal work Λ. |
Tuesday, November 9, 2021 2:24PM - 2:36PM |
JO04.00003: Computational Modeling of the Target Mounting Stalk in Direct-drive Implosions Kenneth Anderson, Edward C Hansen, John A Marozas, Timothy J Collins, Valeri N Goncharov, Michael M Marinak, Scott M Sepke The effect of the target-mounting stalk on the symmetry and performance of directly driven inertial confinement implosions has been a topic of open debate. Previous simulations have predicted up to 50% yield degradation caused by the presence of the stalk mount,[1][2] whereas experiments typically have shown little effect except when combined with target offset.[3] The stalk may contribute to implosion nonuniformity both via a mass perturbation arising from the stalk itself and the glue spot used to attach the stalk to the capsule, as well as through a shadowing of the laser beams incident on the capsule surface. We will investigate the impact of the mounting stalk through HYDRA simulations of OMEGA cryogenic implosions. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856. [1] I. V. Igumenshchev et al., Phys. Plasmas 16, 082701 (2009). [2] B. M. Haines et al., Phys. Plasmas 23, 072709 (2016). [3] M. Gatu Johnson et al., Phys. Plasmas 27, 032704 (2020). |
Tuesday, November 9, 2021 2:36PM - 2:48PM |
JO04.00004: Analysis of Modulations Observed in X-Ray Self-Emission Images of OMEGA Direct-Drive Inertial Confinement Fusion Implosions Tirtha R Joshi, Rahul C Shah, Wolfgang R Theobald, Igor Igumenshchev, Joshua Baltazar, Duc M Cao, Sean P Regan We discuss the observations of a pattern of the x-ray self-emission corresponding to the overlapping of laser beams on OMEGA spherical direct-drive implosions using a small-spot distributed phase plate (SG5-650) in all 60 laser beams. The targets were spherical plastic shells filled with deuterium gas, and the diagnostic used to record the gated x-ray self-emission images was an x-ray framing camera. The state-of-the-art 3-D ASTER simulations performed for these implosions with and without including the laser-imprinting effect also show qualitatively similar patterns in the self-emission images. Inclusion of the laser-imprinting effect in the simulations increases the contrast in the images by about 5% compared to the simulations performed without imprinting. Analyses of the total intensity distributions in the self-emission images suggest that these emission patterns in the images arise from the x-ray self-emission from shell (toward the line of sight). The measurements show greater contrast than in simulated self-emission images, thereby suggesting that beam-mode–induced hydrodynamic perturbations may be underestimated. The difference in electron temperature and density gradients in the experimental and simulated implosions has been inferred using the emission discrepancies in simulated and experimental images. |
Tuesday, November 9, 2021 2:48PM - 3:00PM |
JO04.00005: Measurements of 3D hydrodynamic instabilities at ablation front in indirect-drive ICF implosions on NIF Vladimir Smalyuk, Chris Weber, Gareth N Hall, Otto L Landen Hydrodynamic instabilities are major factor in degradation of spherical implosions in inertial confinement fusion (ICF). Instabilities at ablation front are some key contributors to overall stability of x-ray driven implosions. We present results of hydrodynamic instability experiments with high-density-carbon (HDC) ablators on National Ignition Facility (NIF). The unstable growth of 3D perturbations was measured with x-ray radiography using Hydrodynamic Growth Radiography (HGR) platform and crystal backlighter imager (CBI). The dependence of the instability growth on initial perturbations at outer capsule surface will be presented. |
Tuesday, November 9, 2021 3:00PM - 3:12PM |
JO04.00006: Measuring Isotropic Fuel-Ablator Mix at Stagnation of Cryogenically Layered Capsule Implosions at the NIF Benjamin Bachmann, Steve A MacLaren, Suhas Bhandarkar, Travis Briggs, Justin Buscho, Dan T Casey, Laurent Divol, Tilo Doeppner, David Fittinghoff, Matthew Freeman, Steven W Haan, Gareth N Hall, Bruce Hammel, Edward P Hartouni, Nobuhiko Izumi, Steve Johnson, Verena Geppert-Kleinrath, Shahab F Khan, Bernard Kozioziemski, Christine Krauland, Otto L Landen, Brian J MacGowan, Derek Mariscal, Edward V Marley, Laurent P Masse, Kevin Meaney, Gregory Mellos, Alastair S Moore, Arthur E Pak, Pravesh K Patel, Mark Ratledge, Neal Rice, Michael S Rubery, Jay Salmonson, Jim Sater, David J Schlossberg, Marilyn B Schneider, Vladimir Smalyuk, Clement A Trosseille, Petr L Volegov, Chris Weber, Jackson J Williams, Brandon Woodworth, Andrew Wray Fuel-ablator mix in ICF implosions is a major degradation mechanism of nuclear fusion performance. At the same time, it is one of the most challenging mechanisms to measure at capsule stagnation. While significant progress has been made to quantify localized mix, previous studies of isotropic fuel-ablator mix have been limited to the early implosion phase. Here we report on the first measurements carried out at the NIF, directly probing isotropic fuel-ablator mix at capsule stagnation between a CH shell with a roughened inner surface and a cryogenic fuel layer. We use the separated reactants technique which employs an HT fuel layer of varying thickness and an inner layer of deuterated plastic (CD) such that the DT neutron signal at stagnation represents a quantitative measure of mixing between shell and fuel. We observe a significant increase in isotropically mixed ablator material when reducing the ice layer thickness from 29 to 17 micrometer because of increased propagation of fuel-ablator instabilities through the thinner ice layer. These measurements improve our understanding of fuel-ablator mix at stagnation by deriving an experimental scaling with ice layer thickness and benchmarking various mix models in-line with state-of-the art radiation hydrodynamics simulations. |
Tuesday, November 9, 2021 3:12PM - 3:24PM |
JO04.00007: Internal Perturbation Evolution and Amplification During the Early Phase of Inertial Confinement Fusion Implosions Samuel C Miller, Valeri N Goncharov Performance degradation in direct-drive inertial confinement fusion (ICF) implosions can be caused by several effects including Rayleigh–Taylor (RT) instability growth. Defects in ICF targets such as internal voids and surface roughness create seeds for RT growth during the initial phase of implosions, and the perturbations created by these defects are propagated along acoustic waves. These perturbations can travel along reflected rarefaction waves or compression waves and become amplified because of converging characteristics. A comprehensive understanding of this wave evolution and perturbation amplification is essential to characterize the impact of internal defects on hydrodynamic-instability seeding. The evolution and amplification of 2-D perturbations within a planar target during early implosion phases will be presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856. |
Tuesday, November 9, 2021 3:24PM - 3:36PM |
JO04.00008: Carbon Grain Structure Impacts on Fuel-Ablator Mixing Seth Davidovits, Chris Weber, Daniel S Clark High density carbon (HDC) ablators used in inertial confinement fusion (ICF) implosions have a microscale or nanoscale grain structure. This grain structure, which has an associated density inhomogeneity, is known to perturb shocks passing through the HDC. Here we use high-resolution simulations to study mixing processes associated with these perturbations in ICF implosions at the interface between an HDC ablator and a deuterium-tritium fuel layer. In particular, we find interaction between grain-seeded perturbations and thermal-conduction-driven density gradients near the interface. Further, we show how different strategies for de-resolving the grain structure to reduce computational cost influence the magnitude of post-shock perturbations and the degree of mixing. |
Tuesday, November 9, 2021 3:36PM - 3:48PM |
JO04.00009: Modeling the interactions of multiple voids in Inertial Confinement Fusions Implosions Ryan C Nora, Daniel S Clark, Laurent P Masse, Brian M Haines, Alison R Christopherson Hollow, nearly spherical capsule imperfections (otherwise known as “voids”) in high-density-carbon ablators may be one of the sources of significant degradations in inertial confinement fusion (ICF) implosions. The size and depth (from the outer ablator surface) of individual voids can lead to multiple effects; from no apparent effect, to jetting of ablator material into the hot spot at stagnation, to increased interface mixing. Previous work investigating the correlation between observed voids and additional x-ray mixing [1,2] assumes these voids do not interact with each other. This work examines this assumption using 2D and 3D HYDRA [3] simulations to quantify the interaction lengths and effects on ICF implosions for multiply interacting voids. Finally, we will show the results of 3D simulations initialized with void measurements taken by target fabrication to compare with experimental observations. |
Tuesday, November 9, 2021 3:48PM - 4:00PM |
JO04.00010: Manufacturing Process and Characterization Overview of a Cylindrical CH ablator with seamlessly embedded thin aluminum band for use in Omega and NIF Experiments. Alexandria Strickland, Thomas Day, Derek Schmidt, Joshua P Sauppe, Sasikumar Palaniyappan, Brian M Patterson, Tana Morrow, Christopher Wilson, Lynne A Goodwin, Patrick Donovan, Randall B Randolph, Chris E Hamilton, Stephanie Edwards, Frank Fierro, Theresa Quintana
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Tuesday, November 9, 2021 4:00PM - 4:12PM |
JO04.00011: High Convergence Gas-Filled Cylindrical Implosions at the OMEGA Laser Facility Sasi Palaniyappan, Joshua P Sauppe, Kirk A Flippo, Lynn Kot, Thomas Day, Alex Strickland, Derek Schmidt, Rebecca Roycroft, John L Kline Deceleration-phase Rayleigh-Taylor instability (RTI) growth during the inertial confinement fusion (ICF) implosions affects the implosion performance significantly as it mixes the cold ablator material into the fuel. Precise measurements of such instability growth are essential for both validating the existing simulation codes and improving our predictive capability. RTI measurements on the inner surface of a spherical shell are limited and are often inferred indirectly at limited convergence. In contrast, cylindrical implosions allow for direct and precise measurements of the inner surface while retaining the effects of convergence, which are known to modify RTI growth rates through Bell-Plesset effects. Earlier we have demonstrated RTI growth to be scale-invariant between the cylindrical targets at OMEGA and similar targets at the NIF that are scaled up by a factor of 3 in the radial dimension at a relatively low convergence of CR~2.5 using 300 mg/cc foam filled cylindrical implosions. Here we demonstrate 10 mg/cc propane gas filled cylindrical implosions at the OMEGA laser facility reaching a CR of 7 at re-shock. We compare the RTI growth measurements to 2D xRAGE calculations. Designs for similar higher convergence cylindrical implosions at NIF are currently underway. |
Tuesday, November 9, 2021 4:12PM - 4:24PM |
JO04.00012: Theory and Modeling of Blast-Wave–Driven Perturbation Growth in OMEGA Planar Experiments Timothy J Collins, Philip M Nilson, Reuben Epstein, David Bishel, David A Chin, John J Ruby, Joshua Kendrick, Dale Guy, Steven T Ivancic, Frederic J Marshall, Christian Stoeckl, Valeri N Goncharov, Dustin H Froula Decaying shock waves play an important dynamic and energetic role in a variety of contexts, from expanding supernova-remnant outflows to imploding inertial confinement fusion targets. In the latter, decaying shocks are used to set the fuel and ablator adiabats but also result in instability growth and potential mixing at the fuel–ablator interface. We report here on 2-D modeling with radiation-hydrodynamics code DRACO of instability growth of an interface between a doped-plastic pusher and low-density foam caused by a laser-generated blast wave in planar OMEGA experiments. Simulated radiographs generated with Spect3D were compared with high-resolution 4.75-keV experimental radiographs obtained using a Fresnel phase zone-plate imaging system. Images obtained many nanoseconds after the end of the laser pulse reveal comparable, highly nonlinear growth caused by both the Richtmyer–Meshkov and Rayleigh-Taylor instabilities during a phase in which the vorticity is effectively “frozen” into the plasma. Discrepancies in the observed and modeled post-shock compressibility will also be discussed. |
Tuesday, November 9, 2021 4:24PM - 4:36PM |
JO04.00013: Complementary Optical and Radiographic Measurement of Laser Imprint Mitigation on Nike Max Karasik, Calvin Zulick, James L Weaver, Jaechul Oh, Andrew J Schmitt, Yefim Aglitskiy, Stephen P Obenschain Laser imprint mitigation using hybrid (indirect-direct) drive with a high-Z coating has been shown to have an order-of-magnitude reduction in the laser non-uniformity seeding of hydrodynamic instabilities on the Nike KrF laser [Obenschain. PoP 9, 9, 2234 (2002); Karasik, PRL 114, 085001 (2015), https://doi.org/10.1063/1.1464541, https://doi.org/10.1103/PhysRevLett.114.085001] and on Omega EP 3ω Nd:glass laser [Karasik, PoP 28, 032710 (2021), https://doi.org/10.1063/5.0042454]. Raleigh-Taylor amplification of laser imprint has been required to diagnose this using radiography. Recent installation of high resolution 2D VISAR on Nike allowed sensitive measurement of the imprint reduction due to the high-Z coating independent of RT amplification [J. Oh, PoP 28, 032704 (2021), https://doi.org/10.1063/5.0039395]. Reduction in imprint seeding is also expected with increased laser bandwidth (shorter coherence time). Measurements of imprint for ISI smoothing with bandwidths in the range 0.3 – 3 THz on Nike will be presented and compared with high resolution FASTrad3D simulations. Work is supported by the US DOE/NNSA. |
Tuesday, November 9, 2021 4:36PM - 4:48PM |
JO04.00014: Hydrodynamic Growth of Perturbations Seeded by Isolated Defects Calvin Zulick, Yefim Aglitskiy, Max Karasik, Andrew J Schmitt, Alexander L Velikovich, Stephen P Obenschain The hydrodynamic growth of pre-imposed isolated surface defects has been measured on the Nike laser. The defects had characteristic sizes of < 1 to 10's of μm, consistent with |
Tuesday, November 9, 2021 4:48PM - 5:00PM |
JO04.00015: Planar-Foil Laser-Imprint Experiments at the National Ignition Facility Alexander Shvydky, Jonathan L Peebles, Michael J Rosenberg, Andrei V Maximov, Kenneth Anderson, Valeri N Goncharov, John A Marozas, Patrick m McKenty, Sean P Regan, Thomas C Sangster, Matthias Hohenberger, Jean-Michel G Di Nicola, Joseph M Koning, Michael M Marinak, Laurent P Masse, Max Karasik, Luca Antonelli Control of shell nonuniformities imprinted by the laser and amplified by hydrodynamic instabilities in the imploding target is critical for the success of direct-drive ignition at the National Ignition Faciliy (NIF). To study laser imprinting, we performed experiments that employed flat and corrugated planar CH foils driven with a single NIF beam. Face-on x-ray radiography was used to measure optical depth variations from which the amplitudes of the foil areal-density modulations were obtained. Simultaneous side-on radiography was used to measure the shell trajectory. Results of 3-D radiation-hydrodynamic code HYDRA [1] simulations of growth of imprint-seeded and surface-imposed perturbations as well as the shell trajectory are presented and compared with the experimental data. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856 and under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344 [1] M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001). |
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