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The introduction of a sample of carbon, for example a disk or "puck", near an imploding DT- filled capsule creates a source of 12C gamma rays that can serve as a reference for calibrating the response of the Gamma Reaction History (GRH) detector [1]. Such calibration is important in the measurement of ablator areal density (ρR)abl in plastic-ablator DT-filled capsules at OMEGA [2], by allowing (ρR)abl to be inferred as a function of ratios of signals rather than from absolute measurements of signal magnitudes. Systematic uncertainties in signal measurements and detector responses therefore cancel, permitting more accurate measurements of (ρR)abl. [ABSTRACT FROM AUTHOR]

The effect of anisotropic diffusion on hydrodynamic instabilities in the context of Inertial Confinement Fusion (ICF) flows is numerically assessed. This anisotropy occurs in indirect-drive when laminated ablators are used to modify the lateral transport [1, 2]. In direct-drive, non-local transport mechanisms and magnetic fields may modify the lateral conduction [3]. In this work, numerical simulations obtained with the code PERLE [4], dedicated to linear stability analysis, are compared with previous theoretical results [1]. In these approaches, the diffusion anisotropy can be controlled by a characteristic coefficient which enables a comprehensive study. This work provides new results on the ablative Rayleigh-Taylor (RT), ablative Richtmyer-Meshkov (RM) and Darrieus-Landau (DL) instabilities. [ABSTRACT FROM AUTHOR]

A 2-D Eulerian code with a turbulent mix model was used for the first time to model a set of plastic (CH) ablator capsules with 15 µm thick CH shells. Our simulations of these capsules do a reasonable job of matching the implosion radius versus time, self-emitting core radius, and have an experiment/simulation yield ratio that is about 0.24. [ABSTRACT FROM AUTHOR]

Growth of hydrodynamic instabilities at the interfaces of inertial confinement fusion capsules (ICF) due to ablator and fuel non-uniformities are a primary concern for the ICF program. Recently, observed jetting and parasitic mix into the fuel were attributed to isolated defects on the outer surface of the capsule. Strategies for mitigation of these defects exist, however, they require reduced uncertainties in Equation of State (EOS) models prior to invoking them. In light of this, we have begun a campaign to measure the growth of isolated defects (bumps) due to x-ray ablation Richtmyer-Meshkov in plastic ablators to validate these models. Experiments used hohlraums with radiation temperatures near 70 eV driven by 15 beams from the Omega laser (Laboratory for Laser Energetics, University of Rochester, NY), which sent a ~1.25Mbar shock into a planar CH target placed over one laser entrance hole. Targets consisted of 2-D arrays of quasi-gaussian bumps (10 microns tall, 34 microns FWHM) deposited on the surface facing into the hohlraum. On-axis radiography with a saran (Cl Heα - 2.76 keV) backlighter was used to measure bump evolution prior to shock breakout. Shock speed measurements were also performed to determine target conditions. Simulations using the LEOS 5310 and SESAME 7592 models required the simulated laser power be turned down to 80 and 88%, respectively to match observed shock speeds. Both LEOS 5310 and SESAME 7592 simulations agreed with measured bump areal densities out to 6 ns where ablative RM oscillations were observed in previous laser-driven experiments, but did not occur in the x-ray driven case. The QEOS model, conversely, over predicted shock speeds and under predicted areal density in the bump. [ABSTRACT FROM AUTHOR]

Post-shot modeling of NIF capsule implosions was performed in order to validate our physical and numerical models. Cryogenic layered target implosions and experiments with surrogate targets produce an abundance of capsule performance data including implosion velocity, remaining ablator mass, times of peak x-ray and neutron emission, core image size, core symmetry, neutron yield, and x-ray spectra. We have attempted to match the integrated data set with capsule-only simulations by adjusting the drive and other physics parameters within expected uncertainties. The simulations include interface roughness, time-dependent symmetry, and a model of mix. We were able to match many of the measured performance parameters for a selection of shots. [ABSTRACT FROM AUTHOR]

Indirectly driven Symcap capsules are used at the NIF to obtain information about ignition capsule implosion performance, in particular shape. Symcaps replace the cryogenic fuel layer with an equivalent ablator mass and can be similarly diagnosed. Symcaps are good symmetry surrogates to an ignition capsule after the peak of the drive, radiation-hydrodynamics simulations predict that doping of the symcaps vary the behavior of the implosion. We compare the equatorial shapes of a symcap doped with Si or Ge, as well as examine the reproducibility of the shape measurement using two symcaps with the same hohlraum and laser conditions. [ABSTRACT FROM AUTHOR]

A detailed simulation-based model of the June 2011 National Ignition Campaign (NIC) cryogenic DT experiments is presented. The model is based on integrated hohlraum-capsule simulations that utilize the best available models for the hohlraum wall, ablator, and DT equations of state and opacities. The calculated radiation drive was adjusted by changing the input laser power to match the experimentally measured shock speeds, shock merger times, peak implosion velocity, and bangtime. The crossbeam energy transfer model was tuned to match the measured time-dependent symmetry. Mid-mode mix was included by directly modeling the ablator and ice surface perturbations up to mode 60. Simulated experimental values were extracted from the simulation and compared against the experiment. The model adjustments brought much of the simulated data into closer agreement with the experiment, with the notable exception of the measured yields, which were 15-40% of the calculated yields. [ABSTRACT FROM AUTHOR]

The overall goal of the indirect-drive inertial confinement fusion tuning campaigns is to maximize the probability of ignition by experimentally correcting for likely residual uncertainties in the implosion and hohlraum physics used in our radiation-hydrodynamic computational models, and by checking for and resolving unexpected shot-to-shot variability in performance. This has been started successfully using a variety of surrogate capsules that set key laser, hohlraum and capsule parameters to maximize ignition capsule implosion velocity, while minimizing fuel adiabat, core shape asymmetry and ablator-fuel mix. [ABSTRACT FROM AUTHOR]