Fourier-space image processing for spherical experiments on OMEGA (invited)

Smalyuk, V. A.; Boehly, T. R.; Iwan, L.; Kessler, T. J.; Knauer, J. P.; Marshall, F. J.; Meyerhofer, D. D.; Stoeckl, C.; Yaakobi, B.; Bradley, D. K.

doi:10.1063/1.1315642

Cited by 22 publications

(14 citation statements)

References 9 publications

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“…The spatial blurring includes the spatial resolution of the pinhole camera and the framing camera. Figure 7 shows the calculated (at an x-ray energy of 6.7 keV) optical transfer function (OTF) of the 20 µm pinhole camera (solid curve) [16] and the measured OTF of the framing camera (dashed curve) [12] . One would multiply the two curves to obtain the OTF of both the pinhole camera and the framing camera.…”

Section: Simulated Imagesmentioning

confidence: 99%

“…One would multiply the two curves to obtain the OTF of both the pinhole camera and the framing camera. The additional blurring effect of the 60 µm scanning aperture of the densitometer [16] , used to scan the film of the framing camera, was also included. Figure 8 shows the OD Fourier spectra of the simulated images without (solid curve) and including (dashed curve) the effects of spatial resolution.…”

Section: Simulated Imagesmentioning

confidence: 99%

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Hydrodynamic instability experiments with three-dimensional modulations at the National Ignition Facility

Smalyuk

Weber

Casey

et al. 2015

High Pow Laser Sci Eng

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The first hydrodynamic instability growth measurements with three-dimensional (3D) surface-roughness modulations were performed on CH shell spherical implosions at the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)]. The initial capsule outer-surface amplitudes were increased approximately four times, compared with the standard specifications, to increase the signal-to-noise ratio, helping to qualify a technique for measuring small 3D modulations. The instability growth measurements were performed using x-ray through-foil radiography based on time-resolved pinhole imaging. Averaging over 15 similar images significantly increased the signal-to-noise ratio, making possible a comparison with 3D simulations. At a convergence ratio of ∼2.4, the measured modulation levels were ∼3 times larger than those simulated based on the growth of the known imposed initial surface modulations. Several hypotheses are discussed, including increased instability growth due to modulations of the oxygen content in the bulk of the capsule. Future experiments will be focused on measurements with standard 3D 'nativeroughness' capsules as well as with deliberately imposed oxygen modulations.

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Section: Simulated Imagesmentioning

confidence: 99%

Section: Simulated Imagesmentioning

confidence: 99%

Hydrodynamic instability experiments with three-dimensional modulations at the National Ignition Facility

Smalyuk

Weber

Casey

et al. 2015

High Pow Laser Sci Eng

View full text Add to dashboard Cite

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“…In contrast, x-ray images primarily record emissions from heated CH near the fuel-shell interface. 14 In addition, the burn data are time integrated while the x-ray images are gated with a 40-ps window 16 (and show slightly decreasing size during the ~ 150-ps burn interval). Figure 2 provides a comparison between burn data and an x-ray image taken approximately at peak burn time for shot 35176 (analyzed in Fig.…”

Section: B Comparing Nuclear Burn Data With X-ray Datamentioning

confidence: 99%

“…X-ray framing cameras were used to obtain 4 -5 keV x-ray emission images [14][15][16] at 58-ps time intervals using 12x magnification and 40-ps integration times. At the time of peak proton production, the x-ray images represent primarily continuum emission from the heated inner portion of the shell material and can be used to estimate the radius of the fuel-shell interface as described in ref.…”

Section: Experimental Conditionsmentioning

confidence: 99%

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Measured dependence of nuclear burn region size on implosion parameters in inertial confinement fusion experiments

et al. 2006

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Radial profiles of nuclear burn in directly-driven, inertial-confinement-fusion implosions have been systematically studied for the first time using a proton emission imaging system sensitive to energetic 14.7-MeV protons from the fusion of deuterium (D) and 3-helium ( 3 He) at the OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Experimental parameters that were varied include capsule size, shell composition and thickness, gas fill pressure, and laser energy. Clear relationships have been identified between changes in a number of these parameters and changes in the size of the burn region, which we characterize here by the median "burn radius" R burn containing half of the total D 3 He reactions. Different laser and capsule parameters resulted in burn radii varying from 20 to 80 µm. For example, reducing the D 3 He fill pressure from 18 to 3.6 atm in capsules with 20-µm-thick CH shells resulted in the mean burn radius changing from 31 µm to 25 µm; this reduction is attributed to increased fuel-shell mix for the more unstable 3.6-atm implosions rather than to increased convergence, because total areal density didn't change very much. Fuel-shell-interface radii estimated from hard (4-5 keV) x-ray images of some of the same implosions were observed to closely track the burn radii. Simulated burn radii produced with 1-D codes agree fairly well with measurements for glass-shell capsules, but are systematically smaller than measurements for CH-shell capsules. A search for possible sources of systematic measurement error that could account for this discrepancy has been unsuccessful. Possible physical sources of discrepancies are mix, hydrodynamic instabilities and/or preheat not included in the 1-D code. Since measured burn-region sizes indicate where fusion actually occurs as a consequence of all the complicated processes that affect capsule implosion dynamics, they provide exacting tests of simulations. a) seguin@mit.edu b) Also Visiting Senior Scientist, Laboratory for Laser Energetics, University of Rochester. c) Also Departments of Mechanical Engineering, Physics and Astronomy, University of Rochester.Byline: ICF burn region measurements 2

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Compressed-shell integrity measurements in spherical implosion experiments

et al. 2001

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The shell integrity near peak compression of spherical implosions using the 60-beam, 30-kJ UV OMEGA laser system [Opt. Commun. 133, 495 (1997)] has been measured. Hot core emission backlights a shell with a thin titanium-doped layer that is imaged at x-ray photon energies above and below the titanium K edge. The x-ray intensity ratio between the two images is related to perturbations in the cold, or absorbing, part of the shell. The measured cold-shell areal-density modulations, integrated over the time of peak compression, are of the order of 25% to 50% with nonuniformity spectra peaked at spatial wavelengths of 30 to 50 μm and with the smallest detectable nonuniformity features extending down to spatial wavelengths of 12 to 15 μm. Hot-shell areal-density modulations of the emitting part of the shell (inner edge) are of the order of 13% to 20%. The measured shell modulations are in agreement with the results of two-dimensional simulations that include initial shell perturbations, imprinted shell modulations due to nonuniformities in a single laser beam, and a beam-to-beam energy imbalance in the laser drive.

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Fourier-space image processing for spherical experiments on OMEGA (invited)

Cited by 22 publications

References 9 publications

Hydrodynamic instability experiments with three-dimensional modulations at the National Ignition Facility

Hydrodynamic instability experiments with three-dimensional modulations at the National Ignition Facility

Measured dependence of nuclear burn region size on implosion parameters in inertial confinement fusion experiments

Compressed-shell integrity measurements in spherical implosion experiments

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