Extracting core shape from x-ray images at the National Ignition Facility

Glenn, S.; Benedetti, L. R.; Bradley, D. K.; Hammel, B. A.; Izumi, N.; Khan, S. F.; Kyrala, G. A.; Ma, T.; Milovich, J. L.; Pak, A.; Smalyuk, V. A.; Tommasini, R.; Town, R. P. J.

doi:10.1063/1.4731743

Cited by 40 publications

(13 citation statements)

References 11 publications

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“…One would expect this high energy x-ray image to be consistent with a toroidal primary neutron image, as only the hottest regions of the nuclear fuel will generate fusion neutrons and this region will also be the brightest emitter of x-rays. 19,20 A comparison of the raw image to the reconstructed source shows that a significant level of distortions has been removed to form the source neutron distribution. The fact that the resulting source reconstruction is consistent with the orthogonal x-ray image demonstrates that this method of reconstruction is effective for this application.…”

Section: Application Of Mle Algorithms To Datamentioning

confidence: 99%

Neutron source reconstruction from pinhole imaging at National Ignition Facility

Volegov

Danly

Fittinghoff

et al. 2014

Review of Scientific Instruments

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The neutron imaging system at the National Ignition Facility (NIF) is an important diagnostic tool for measuring the two-dimensional size and shape of the neutrons produced in the burning deuterium-tritium plasma during the ignition stage of inertial confinement fusion (ICF) implosions at NIF. Since the neutron source is small (∼100 μm) and neutrons are deeply penetrating (>3 cm) in all materials, the apertures used to achieve the desired 10-μm resolution are 20-cm long, single-sided tapers in gold. These apertures, which have triangular cross sections, produce distortions in the image, and the extended nature of the pinhole results in a non-stationary or spatially varying point spread function across the pinhole field of view. In this work, we have used iterative Maximum Likelihood techniques to remove the non-stationary distortions introduced by the aperture to reconstruct the underlying neutron source distributions. We present the detailed algorithms used for these reconstructions, the stopping criteria used and reconstructed sources from data collected at NIF with a discussion of the neutron imaging performance in light of other diagnostics.

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Section: Application Of Mle Algorithms To Datamentioning

confidence: 99%

Neutron source reconstruction from pinhole imaging at National Ignition Facility

Volegov

Danly

Fittinghoff

et al. 2014

Review of Scientific Instruments

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“…The temporal resolution of the framing camera was 100 ps, while spatial resolution of the slit images was 20 lm. The slit and pinholes were positioned 100 mm from the target center, while the detector, a framing camera, 50 was located 1300 mm from the target center, giving a magnification of $12 for the imaging system. Pinhole images on the right-hand-side of the Fig.…”

Section: Ablation-front Instability Experimentsmentioning

confidence: 99%

Hydrodynamic instability growth and mix experiments at the National Ignition Facility

et al. 2014

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Hydrodynamic instability growth and its effects on implosion performance were studied at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 443, 2841 (2004)]. Implosion performance and mix have been measured at peak compression using plastic shells filled with tritium gas and containing embedded localized carbon-deuterium diagnostic layers in various locations in the ablator. Neutron yield and ion temperature of the deuterium-tritium fusion reactions were used as a measure of shell-gas mix, while neutron yield of the tritium-tritium fusion reaction was used as a measure of implosion performance. The results have indicated that the low-mode hydrodynamic instabilities due to surface roughness were the primary culprits for yield degradation, with atomic ablator-gas mix playing a secondary role. In addition, spherical shells with pre-imposed 2D modulations were used to measure instability growth in the acceleration phase of the implosions. The capsules were imploded using ignition-relevant laser pulses, and ablation-front modulation growth was measured using x-ray radiography for a shell convergence ratio of ∼2. The measured growth was in good agreement with that predicted, thus validating simulations for the fastest growing modulations with mode numbers up to 90 in the acceleration phase. Future experiments will be focused on measurements at higher convergence, higher-mode number modulations, and growth occurring during the deceleration phase.

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“…Capsule x-ray bang times 30,31 were $22.55 6 0.10 ns, all within 100 ps. We will focus upon capsule performance metrics of DT, DD, TT neutron yield, [32][33][34] neutron time-of-flight measurements 35 of ion temperature 36 and down-scatter ratio (DSR), temporal burn width from x-rays 37 or DT gammas, 38,39 and x-ray 40 and neutron image size and shape. 41 DSR is the ratio of neutrons in the 10-12 MeV energy range to those in the 13-15 MeV range, and is diagnostic of fuel column density.…”

Section: Simulations Of Implosions With CD Layersmentioning

confidence: 99%

Simulations of indirectly driven gas-filled capsules at the National Ignition Facility

et al. 2014

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Gas-filled capsules imploded with indirect drive on the National Ignition Facility have been employed as symmetry surrogates for cryogenic-layered ignition capsules and to explore interfacial mix. Plastic capsules containing deuterated layers and filled with tritium gas provide a direct measure of mix of ablator into the gas fuel. Other plastic capsules have employed DT or D3He gas fill. We present the results of two-dimensional simulations of gas-filled capsule implosions with known degradation sources represented as in modeling of inertial confinement fusion ignition designs; these are time-dependent drive asymmetry, the capsule support tent, roughness at material interfaces, and prescribed gas-ablator interface mix. Unlike the case of cryogenic-layered implosions, many observables of gas-filled implosions are in reasonable agreement with predictions of these simulations. Yields of TT and DT neutrons as well as other x-ray and nuclear diagnostics are matched for CD-layered implosions. Yields of DT-filled capsules are over-predicted by factors of 1.4–2, while D3He capsule yields are matched, as well as other metrics for both capsule types.

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Extracting core shape from x-ray images at the National Ignition Facility

Cited by 40 publications

References 11 publications

Neutron source reconstruction from pinhole imaging at National Ignition Facility

Neutron source reconstruction from pinhole imaging at National Ignition Facility

Hydrodynamic instability growth and mix experiments at the National Ignition Facility

Simulations of indirectly driven gas-filled capsules at the National Ignition Facility

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