Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session GO7: ICF Mix |
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Chair: Harry Robey, Lawrence Livermore National Laboratory Room: Governor's Square 12 |
Tuesday, November 12, 2013 9:30AM - 9:42AM |
GO7.00001: Progress toward development of a platform for studying burn in the presence of mix on the National Ignition Facility T.J. Murphy, G.A. Kyrala, P.A. Bradley, N.S. Krasheninnikova, J.A. Cobble, I.L. Tregillis, K.A.D. Obrey, S.C. Hsu, R.C. Shah, P. Hakel, J.L. Kline, G.P. Grim, J.A. Baumgaertel, M.J. Schmitt, R.J. Kanzleiter, S.H. Batha Mix of shell material into ICF capsule fuel can degrade implosion performance through a number of mechanisms. One way is by dilution of the fusion fuel, which affects performance by an amount that is dependent on the degree of mix at the atomic level. Experiments are underway to quantify the mix of shell material into fuel using directly driven capsules on the National Ignition Facility. Deuterated plastic shells will be utilized with tritium fill so that the production of DT neutrons is indicative of mix at the atomic level. Neutron imaging will locate the burn region and spectroscopic imaging of the doped layers will reveal the location, temperature, and density of the shell material. Correlation of the two will be used to determine the degree of atomic mixing of the shell into the fuel and will be compared to models. This talk will review progress toward the development of an experimental platform to measure burn in the presence of measured mix. [Preview Abstract] |
Tuesday, November 12, 2013 9:42AM - 9:54AM |
GO7.00002: Diagnosing Mix in NIF Polar Direct Drive Capsule Implosions Paul Bradley, T. Murphy, G. Kyrala, N. Krasheninnikova, P. Hakel, M. Schmitt, I. Tregillis, S. Hsu, R. Kanzleiter, K. Obrey, J. Fincke, S. Batha We have investigated the role of turbulent mix in polar direct drive capsule implosions by modeling the a series of such Defect Induced Mix Experiment implosions (fielded in 2012 and 2013) on the National Ignition Facility with a two-dimensional Eulearian radiation-hydrodynamic code. The capsules had an outer diameter of $\sim$2250 microns, were composed of 42 micron thick CH plastic ablators, and filled with 5 atm of deuterium or hydrogen gas. The capsules were imploded using 320 to 670 kJ laser energy in a 2.15 ns flat-top pulse. We use neutron yield and x-ray spectra from a dopant layer as mix diagnostics. The simulated yields, bang times, and ion temperatures follow the experimental trends. We will also show how the simulated spectral emission from the dopant layer compares to the data and how this implies about 1 micron of the shell mixes into the gas. We will discuss what these results imply for the extent of mix in ICF capsules. Work performed by Los Alamos National Laboratory under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the U.S. Department of Energy. [Preview Abstract] |
Tuesday, November 12, 2013 9:54AM - 10:06AM |
GO7.00003: Symmetry Tuning with Cone Powers for Defect Induced Mix Experiment Implosions N. Krasheninnikova, M. Schmitt, T. Murphy, J. Cobble, I. Tregillis, G. Kyrala, P. Bradley, P. Hakel, S. Hsu, R. Kanzleiter, K. Obrey, J. Baumgaertel, S. Batha Recent DIME campaigns have demonstrated the effectiveness of cone power tuning to control the implosion symmetry in PDD configuration. DIME aims to assess the effects of mix on thermonuclear burn during a thin-shell capsule implosion. Plastic shell capsules doped with mid-Z material and filled with 5 atm of DD, are ablatively driven in a PDD laser configuration to a CR of $\sim$ 7. Time-gated, spectrally and spatially resolved, dopant emission images characterize mix and temperature morphology during the implosion, while neutron diagnostics concurrently give the information about burn. Symmetry should be maintained throughout the implosions to achieve high neutron yield and optimum spectroscopic signal. 2D and 3D computer simulations using code HYDRA were performed to validate and optimize implosion symmetry using cone power tuning. In particular, Omega campaign confirmed P2 tunability with cone powers while experiments on NIF demonstrated that by reducing the energy in polar cones P2 was reduced to \textless~1{\%}. However, during NIF campaigns, self-emission images revealed a complex internal structure around the equator, which was not seen in HYDRA simulations and could be attributed to LPI effects. Subsequent DIME campaigns on NIF were able to eliminate this equatorial feature by reducing the laser drive substantiating the LPI hypothesis. [Preview Abstract] |
Tuesday, November 12, 2013 10:06AM - 10:18AM |
GO7.00004: Symmetry Tuning of Polar-Direct-Drive Implosions on OMEGA S. Hsu, J. Cobble, T. Murphy, N. Krasheninnikova, J. Baumgaertel, P. Bradley, P. Hakel, R. Kanzleiter, M. Schmitt, R. Shah, I. Tregillis, R. Mancini, H. Johns, T. Joshi, D. Mayes, S. Nasewicz Three laser cone energy balances and two laser pointings were used over two shot days on OMEGA to evaluate our control of symmetry for polar-direct-drive implosions, and to compare against the predictions of simulations. The spherical targets had 870-$\mu$m outer diameter, 17-$\mu$m thick CH shell, and 5-atm DD gas fill (nominal values). Various dopant combinations were used in both the shell (Ti and V) and gas (Ar). The primary diagnostic for evaluating implosion symmetry was backlit radiography imaged by an x-ray framing camera (day 1) and the LANL large format camera (day 2). For the secondary objective of evaluating shell-mix as a function of laser settings, we used a combination of x-ray spectral instruments including XRS, SSCA, and two MMI's. Neutron yields (from NTOF 5.4~m) were in the range $\approx 0.5$--$3\times 10^{10}$ and the burn-averaged $T_i$ was $\approx 3$--4.5~keV\@. This talk focuses on experimental analysis/results on implosion symmetry as a function of variations in laser settings. [Preview Abstract] |
Tuesday, November 12, 2013 10:18AM - 10:30AM |
GO7.00005: Simulation of Direct Drive Targets on Omega and NIF M.J. Schmitt, N.S. Krasheninnikova, P. Hakel, P.A. Bradley, I.L. Tregillis, J.A. Baumgaertel, J.A. Cobble, S.C. Hsu, G.A. Kyrala, T.J. Murphy, R.C. Shah, M. Barrios, S.P. Regan Simulations have been performed of direct-drive gas-filled CH capsules to examine the temperature dependence of the inner surface of the capsule where mix occurs. Various spectral tracers, doped into the inner layer of the capsule, are examined for their effect on capsule implosion characteristics and their ability to provide spectral signatures that can be used to infer the location, temperature and electron density of the mix region of the capsule. Simulations results will be shown including the effect of preheat and mix on heating of the shell near the gas-shell interface. [Preview Abstract] |
Tuesday, November 12, 2013 10:30AM - 10:42AM |
GO7.00006: X-ray spectroscopy of polar-drive implosions at OMEGA Roberto Mancini, H. Johns, T. Joshi, D. Mayes, S. Nasewicz, S. Hsu, J. Cobble, P. Hakel, I. Tregillis, J. Baumgaertel, N. Krasheninnikova, P. Bradley, M. Schmitt In a series of polar-drive implosions performed at OMEGA several x-ray spectrometers were fielded to record the signal from Ar and Ti tracers added to the core and shell, respectively. The instruments included time-integrated (XRS) and streaked (SSCA) spectrometers as well as gated monochromatic imagers (MMI). Analysis of the Ar streaked data produced the time-history of density and temperature in the core. The gated images provided information about symmetry along both the polar axis and the equatorial plane lines-of-sight. In addition, a generalized Abel inversion of narrow-band images and detailed analysis of spatially resolved spectra extracted from spectrally resolved images recorded with MMI produced spatial distirutions of plasma conditions and mix (T. Nagayama et al, Phys. Plasmas \textbf{19}, 082705 (2012)). Comparisons were made with results from post-processed 3D simulations to provide further insight into the interpretation of the experimental results and to constrain the simulation physics model. [Preview Abstract] |
Tuesday, November 12, 2013 10:42AM - 10:54AM |
GO7.00007: ABSTRACT WITHDRAWN |
Tuesday, November 12, 2013 10:54AM - 11:06AM |
GO7.00008: Evaluating the MMI diagnostic on OMEGA direct-drive shots J.A. Baumgaertel, P.A. Bradley, J.A. Cobble, J. Fincke, P. Hakel, S.C. Hsu, R. Kanzleiter, N.S. Krasheninnikova, T.J. Murphy, M.J. Schmitt, R. Shah, I. Tregillis, K. Obrey, R.C. Mancini, T. Joshi, H. Johns, D. Mayes The Defect-Induced Mix Experiment (DIME) project utilized Multiple Monochromatic Imagers (MMI) on symmetric and polar direct-drive shots conducted on the OMEGA laser. The MMI provides spatially and spectrally resolved data of capsule implosions and resultant dopant emissions. The capsules had radii of 430$\mu$m, with CH shells that included an inner layer doped with 1-2 atom$\%$ Ti, and a gas fill of 5 atm deuterium. Simulations of the target implosion by codes HYDRA and RAGE are post-processed with self-emission and MMI synthetic diagnostic tools and quantitatively compared to the MMI data to determine the utility of using it for mix model validation. MMI data shows the location of dopants, which are used to diagnose mix. Sensitivities of synthetic MMI images and yield to laser drive and mix levels are explored. Finally, RAGE results, clean and with mix, are compared with time-dependent streak camera data. This work is supported by US DOE/NNSA, performed at LANL, operated by LANS LLC under contract DE-AC52-06NA25396. [Preview Abstract] |
Tuesday, November 12, 2013 11:06AM - 11:18AM |
GO7.00009: Progress towards monochromatic imaging of mix at the NIF G.A. Kyrala, T.J. Murphy, P.A. Bradley, N.S. Krasheninnikova, I.L. Tregillis, K. Obrey, R.C. Shah, P. Hakel, J.L. Kline, G.P. Grim, M.J. Schmitt, R.J. Kanzleiter, S.P. Regan, M.A. Barrios Mix of non-hydrogenic (Z \textgreater~1) material into the hydrogenic (D and T) ICF capsule fuel degrades implosion performance. The amount of degradation depends on the degree and the spatial distribution of mix. Experiments are underway at NIF to quantify the mix of shell material into fuel using directly driven capsules. CH or CD shells with various dopants, implanted at different depths in the shell are being used to change the amount of dopant mix. Spatially and spectrally resolved emission from the ionized dopants will be used to generate spatially and temporally dependent density and temperature maps of the ionized dopants that are mixed and heated in the core plasma. This information will be used to validate different mix models. This talk will describe the search for the appropriate dopant that gave a radiation spectrum that could be used to record images with the MMI diagnostic. [Preview Abstract] |
Tuesday, November 12, 2013 11:18AM - 11:30AM |
GO7.00010: Investigating Turbulent Mix in HEDLP Experiments Kirk Flippo, Forrest Doss, Eric Loomis, Leslie Welser Sherrill, John Kline, Barbara Devolder, Jim Fincke We report on initial experiments planned for and performed at the NIF and Omega to investigate turbulent mix on a platform initially developed for the Omega laser facility and scaled up for NIF. We are investigating turbulence-driven mix from two colliding shocks and sheared layers resulting from Richtmyre-Meshkov and Kelvin-Helmholtz instabilities, such as those expected in ICF ignition capsule. Two shocks were generated at either end of cylindrical, CH foams, and the evolution of a Ti or Al tracer layer in the center plane or at one end of the foam was measured using point-projection radiography as it is either shocked twice or sheared. Comparison of this data with simulations using the Besnard-Harlow-Rauenzahn (BHR) model is used. BHR is intended for turbulent transport in fluids with large density variations and has the ability to improve our predictive capability for ICF experiments. Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under contract DE-AC52-06NA25396. [Preview Abstract] |
Tuesday, November 12, 2013 11:30AM - 11:42AM |
GO7.00011: High-energy-density compressible turbulence in the counterpropagating shear experiment F.W. Doss, E.N. Loomis, K.A. Flippo, L. Welser-Sherrill, J.R. Fincke The Los Alamos reshock and shear campaign aims to assess models for turbulence under high-energy-density conditions. Experiments carried out on the OMEGA laser facility created high-speed shear regions (80 km/s each side) in CH foam ($\sim$200~mg/cc post-shock) which excited a shear instability and drove the spreading of a high density and temperature ($\sim$1~g/cc, 14~eV) aluminum shear layer. The experiments have been analyzed in the context of the BHR turbulence model (a Reynolds-averaged turbulence model of $k$-$\epsilon$ type extended to include variable density effects) implemented in the RAGE radiation hydrocode. Results confirm that the observed spreading of the layer is due to instability leading to turbulence, that the results of the experiment can be tied to the function of specific model coefficients, and that compressibility effects and large density gradients play an important role, making this data important for the ongoing validation of HED turbulence models. Los Alamos National Laboratory is operated by Los Alamos National Security, LLC for the U.S. DOE NNSA under contract DE-AC52-06NA25396. [Preview Abstract] |
Tuesday, November 12, 2013 11:42AM - 11:54AM |
GO7.00012: 2D Simulations of CD Mix Capsules Jesse Pino, Jeff Greenough, Robert Tipton, Steven Weber, Vladimir Smalyuk, Daniel Casey, Dana Rowley, Bruce Remington The CD Mix campaign is a recent series of experiments to measure atomic ablator-gas mix in capsule implosions on the National Ignition Facility. Plastic capsules containing deuterated plastic (CD) layers were filled with Tritium gas. As the reactants are initially separated, DT fusion yield provides a direct measure of mix in the outer part of the core. By varying the depth of the CD layer, a measure of mix penetration length can be made. We will describe the 2D ARES Arbitrary Lagrangian-Eulerian Radiation Hydrodynamics simulations of these experiments. Imposed surface roughness perturbations are adjusted to match the TT neutron yield from the core of the implosion. To match the DT neutron yield and temperature, two different dynamic mix models are applied: the K-L Reynolds Averaged Navier-Stokes model, and multicomponent Navier-Stokes model. We compare these models and assess their ability to capture the dependence of DT yield on the recession depth of the CD layer. [Preview Abstract] |
Tuesday, November 12, 2013 11:54AM - 12:06PM |
GO7.00013: Measurements of gas/shell mix in implosions at the National Ignition Facility using the CD Symcap platform Daniel Casey, Vladimir Smalyuk, Robert Tipton, Jesse Pino, Gary Grim, Bruce Remington, Dana Rowley, Steve Weber Surrogate implosions play an important role at the National Ignition Facility (NIF) for isolating aspects of the complex physics associated with fully integrated ignition experiments. The newly developed CD Symcap platform has been designed to study gas/shell mix in indirectly driven, pure T-gas filled CH-shell implosions, with 4-$\mu $m thick CD layers. This configuration provides a direct nuclear signature of mix as the DT yield (above a characterized D contamination background) is produced by D from the CD layer in the shell, mixing into the T-gas core. The CD layer can be placed at different locations within the CH shell to probe the depth and extent of mix. In addition, time-gated x-ray images show large brightly-radiating objects traversing through the hotspot around bang-time, which are likely observations of chunks of CH/CD plastic. [Preview Abstract] |
Tuesday, November 12, 2013 12:06PM - 12:18PM |
GO7.00014: Measuring direct drive ICF remaining ablator areal density using a gas Cherenkov detector Michael Rubery, Colin Horsfield, Hans Herrmann, Yongho Kim, Nelson Hoffmann, Joseph Mack, Carl Young, Scott Evans, Tom Sedillo, Steven Caldwell, Elliot Grafil, Wolfgang Stoeffl, James Milnes Neutrons from a compressed direct drive ICF target produce $\gamma$ rays through inelastic interactions with ablator material. The inelastic $\gamma$ intensity is proportional to the remaining ablator areal density at bang time and the neutron yield. Remaining ablator areal density is an important metric for the quality of the implosion and is strongly correlated with fuel temperature and compression. This contribution describes how a background signal routinely measured on the gas Cherenkov detectors can be used to infer the intensity of the low-energy inelastic gammas from the ablator on the same trace as the DT fusion $\gamma$ signal, which is directly proportional to the neutron yield; therefore allowing the remaining ablator areal density to be measured in a self consistent manner. Results from recent experiments at the Omega laser facility designed to prove the technique are discussed. In addition, Monte Carlo modelling shows the technique can be used to measure remaining ablator areal density for both plastic and glass capsules. [Preview Abstract] |
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