Simulations of X-ray emission from Omega fill tube experiments

Langer, Steven H.; Izumi, N.; Dittrich, Thomas; Haan, S. W.

doi:10.1016/j.hedp.2007.02.017

Cited by 6 publications

(4 citation statements)

References 9 publications

(17 reference statements)

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“…4. The connection between stalk (or fill tube) and core shape asymmetry has been reported previously based on broad-band emission image data [19][20][21][22], but our results suggest that isolated defects due to the stalk could also correlate with the asymmetry in T e and n e . Timeresolution of the MMI data was provided by the MCP strips (Fig.…”

supporting

confidence: 73%

Direct asymmetry measurement of temperature and density spatial distributions in inertial confinement fusion plasmas from pinhole space-resolved spectra

et al. 2014

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Two-dimensional space-resolved temperature and density images of an inertial confinement fusion (ICF) implosion core have been diagnosed for the first time. Argon-doped, direct-drive ICF experiments were performed at the Omega Laser Facility and a collection of two-dimensional spaceresolved spectra were obtained from an array of gated, spectrally resolved pinhole images recorded by a multi-monochromatic x-ray imager. Detailed spectral analysis revealed asymmetries of the core not just in shape and size but in the temperature and density spatial distributions, thus characterizing the core with an unprecedented level of detail.Inertial confinement fusion (ICF) is an approach that utilizes laser produced ablation pressure to compress a millimeter-sized spherical shell capsule containing fuel (e.g., deuterium and tritium) and drive the fuel temperature and density to conditions suitable for ignition [1]. The key is a spherically symmetric and stable compression. While state-of-the-art hydrodynamics simulations have been used to design ignition implosions, the challenge of achieving a symmetric implosion experimentally has thus far prevented ICF from reaching the conditions required for successful ignition [2]. Hence, measuring the spatial asymmetry in the temperature and density distributions in the implosion core is crucial for understanding how to make it more symmetric.Several diagnostics were developed in the last few decades in order to investigate implosion core conditions. K-shell line emission spectroscopy using Ar as a tracer has proved to be a powerful tool to extract spaceaveraged electron temperature, T e , and density, n e [3-5]. However, two-dimensional (2-D) space-resolved spectra have never been extracted to study the asymmetries of T e and n e structures in the implosion core. X-ray pinhole imaging of ICF implosion cores has been used to study the shape and size of the core and, in particular, to characterize deviations from spherical symmetry [6,7]. Nevertheless, these images do not reveal the implosion asymmetries in T e and n e distributions.This Letter describes a new spectroscopic method that combines the ideas of Ar tracer spectroscopy and pinhole imaging to extract implosion core images in T e and n e without making symmetry assumptions. These pinhole images are extracted by analyzing a collection of 2-D space-resolved spectra obtained from an array of spectrally resolved core images. The direct measurement of temperature and density asymmetries in the core provides stringent constraints on what actually happens in implosion experiments and can be used to benchmark hydrodynamic simulations. The discussion here focuses on the application to ICF implosion core conditions; nevertheless, the ideas are general. The extraction and analysis of space-resolved spectra from spectrally resolved pinhole images opens up new possibilities for x-ray spectroscopy of high-energy density plasmas.The spectroscopic data were recorded in a series of Ar-doped ICF implosion experiments performed at the Omega Laser ...

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confidence: 73%

Direct asymmetry measurement of temperature and density spatial distributions in inertial confinement fusion plasmas from pinhole space-resolved spectra

et al. 2014

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“…Both jets traversing cores launched from surrogate filltubes and x-ray bright spots spatially correlated with known capsule surface imperfections were observed in 5 lm, 50 ps gated imaging OMEGA experiments using indirectly driven Ti-doped CH shells filled with D 2 . 132 For the CH(Ge) design, we have already confirmed at NIF such signatures of penetration of the Ge dopant using a monochromatic version 133 -ray images from pole and equator view of convergence ratio =15 CH capsules driven by 500 kJ 270 eV peak temperature NIF hohlraums. (b) Extracted P 2 =P 0 (circles) and P 4 =P 0 (diamonds) versus time.…”

Section: Experimental Validation Of Techniquementioning

confidence: 78%

Capsule implosion optimization during the indirect-drive National Ignition Campaign

et al. 2011

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Capsule performance optimization campaigns will be conducted at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, 228 (2004)] to substantially increase the probability of ignition. The campaigns will experimentally correct for residual uncertainties in the implosion and hohlraum physics used in our radiation-hydrodynamic computational models using a variety of ignition capsule surrogates before proceeding to cryogenic-layered implosions and ignition experiments. The quantitative goals and technique options and down selections for the tuning campaigns are first explained. The computationally derived sensitivities to key laser and target parameters are compared to simple analytic models to gain further insight into the physics of the tuning techniques. The results of the validation of the tuning techniques at the OMEGA facility [J. M. Soures et al., Phys. Plasmas 3, 2108 (1996)] under scaled hohlraum and capsule conditions relevant to the ignition design are shown to meet the required sensitivity and accuracy. A roll-up of all expected random and systematic uncertainties in setting the key ignition laser and target parameters due to residual measurement, calibration, cross-coupling, surrogacy, and scale-up errors has been derived that meets the required budget. Finally, we show how the tuning precision will be improved after a number of shots and iterations to meet an acceptable level of residual uncertainty.

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“…Often, at least one object appears correlated to the fill tube orientation implying that a jet seeded by the fill tube is injecting brightly radiating CH into the hotspot. 59,60 The exact origin, the performance impact, and the role of these features in bringing mix into the hotpot is an area of active investigation.…”

Section: X-ray Core Imagingmentioning

confidence: 99%

Development of the CD Symcap platform to study gas-shell mix in implosions at the National Ignition Facility

et al. 2014

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Surrogate implosions play an important role at the National Ignition Facility (NIF) for isolating aspects of the complex physical processes associated with fully integrated ignition experiments. The newly developed CD Symcap platform has been designed to study gas-shell mix in indirectly driven, pure T2-gas filled CH-shell implosions equipped with 4 μm 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. CD layers placed flush with the gas-shell interface and recessed up to 8 μm have shown that most of the mix occurs at the inner-shell surface. In addition, time-gated x-ray images of the hotspot show large brightly radiating objects traversing through the hotspot around bang-time, which are likely chunks of CH/CD plastic. This platform is a powerful new capability at the NIF for understanding mix, one of the key performance issues for ignition experiments.

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Simulations of X-ray emission from Omega fill tube experiments

Cited by 6 publications

References 9 publications

Direct asymmetry measurement of temperature and density spatial distributions in inertial confinement fusion plasmas from pinhole space-resolved spectra

Direct asymmetry measurement of temperature and density spatial distributions in inertial confinement fusion plasmas from pinhole space-resolved spectra

Capsule implosion optimization during the indirect-drive National Ignition Campaign

Development of the CD Symcap platform to study gas-shell mix in implosions at the National Ignition Facility

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