Analysis of mix experiments on Omega

Bradley, P. A.; Cobble, J. A.; Fincke, J. R.; Hsu, S. C.; Maglessen, G.R.; Murphy, T. J.; Schmitt, Mark J.; Tregillis, I. L.; Vinyard, Natalia S; Wysocki, F. J.; Obrey, Kimberly A

doi:10.1051/epjconf/20135904004

Cited by 4 publications

(3 citation statements)

References 13 publications

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“…The bang times of the day 2 capsules are about 100 ps later, just as was seen for the exploding pusher capsules earlier. Those results are described in more detail below and in Bradley et al 21 Thick shell perfect capsule simulations show trends similar to those found for the thin perfect capsules. The YOM values are 0.25 to 0.28, simulated T ion values are 2.6 keV higher than the data (see Fig.…”

Section: Thick Capsulessupporting

confidence: 76%

“…The average difference between the experimental and the simulated radii in a radius versus time plot is 19 lm. 21 This validates the energy sourcing prescription used in place of the absent laser propagation and absorption physics.…”

Section: -5supporting

confidence: 68%

“…The other issue of the Eulerian code is that the mesh is Cartesian and the fluid flow can be distorted along the 0 (equator), 45 , and 90 (pole) positions. These can "imprint" on synthetic x-ray images and this is apparent in Figure 2 of Bradley et al, 21 where the synthetic image has an octagonal shape.…”

Section: Simulationsmentioning

confidence: 96%

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Role of shocks and mix caused by capsule defects

et al. 2012

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Invited Article: Relation between electric and magnetic field structures and their proton-beam images Rev. Sci. Instrum. 83, 101301 (2012) Low intensity dust ion-acoustic shock waves due to dust charge fluctuation in a nonextensive dusty plasma Phys. Plasmas 19, 083705 (2012) Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere Phys. Plasmas 19, 083504 (2012) Additional information on Phys. Plasmas An Eulerian code with a turbulent mix model is used to model a set of plastic (CH) ablator capsules with and without equatorial grooves. The "perfect" capsule results were used to calibrate simulations of capsules with equatorial grooves of different depths that provided information on increasingly perturbed implosions. Simulations with a turbulence model were able to calculate the same yield over mix (YOM) ratio (experiment/mix simulation) of 0.2 to 0.3 for thin (8-lm thick) and thick shell (15-lm thick) capsules with no grooves and thin capsules with shallow grooves. When the capsules have deep grooves, the YOM ratio increases to greater than unity, probably because the deformed shocks focus too strongly on the symmetry axis in our two-dimensional simulations. This is supported by a comparison of simulated and experimental x-ray images. V C 2012 American Institute of Physics. [http://dx.

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Section: Thick Capsulessupporting

confidence: 76%

Section: -5supporting

confidence: 68%

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Role of shocks and mix caused by capsule defects

et al. 2012

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Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations

et al. 2014

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Temporally, spatially, and spectrally resolved x-ray image data from direct-drive implosions on OMEGA were interpreted with the aid of radiation-hydrodynamic simulations. Neither clean calculations nor those using a turbulent mix model can explain fully the observed migration of shell-dopant material (titanium) into the core. Shell-dopant migration was observed via time-dependent, spatially integrated spectra, and spatially and spectrally resolved x-ray images of capsule implosions and resultant dopant emissions. The titanium emission was centrally peaked in narrowband x-ray images. In post-processed clean simulations, the peak titanium emission forms in a ring in self-emission images as the capsule implodes. Post-processed simulations with mix reproduce trends in time-dependent, spatially integrated spectra, as well having centrally peaked Ti emission in synthetic multiple monochromatic imager. However, mix simulations still do not transport Ti to the core as is observed in the experiment. This suggests that phenomena in addition to the turbulent mix must be responsible for the transport of Ti. Simple diffusion estimates are unable to explain the early Ti mix into the core. Mechanisms suggested for further study are capsule surface roughness, illumination non-uniformity, and shock entrainment.

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The effect of mix on capsule yields as a function of shell thickness and gas fill

Bradley

2014

Physics of Plasmas

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An investigation of direct drive capsules with different shell thicknesses and gas fills was conducted to examine the amount of shock induced (Richtmyer-Meshkov) mix versus Rayleigh-Taylor mix from deceleration of the implosion. The RAGE (Eulerian) code with a turbulent mix model was used to model these capsules for neutron yields along with time-dependent mix amounts. The amount of Richtmyer-Meshkov induced mix from the shock breaking out of the shell is about 0.1 μg (0.15 μm of shell material), while the Rayleigh-Taylor mix is of order 1 μg and determines the mixed simulation yield. The simulations were able to calculate a yield over mix (YOM) ratio (experiment/mix simulation) between 0.5 and 1.0 for capsules with shell thicknesses ranging from 7.5 to 20 μm and with gas fills between 3.8 and 20 atm of D2 or DT. The simulated burn averaged Tion values typically lie with 0.5 keV of the data, which is within the measurement error. For capsules with shell thicknesses >25 μm, the YOM values drop to 0.10 ± 0.05, suggesting that some unmodeled effect needs to be accounted for in the thickest capsules.

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Analysis of mix experiments on Omega

Cited by 4 publications

References 13 publications

Role of shocks and mix caused by capsule defects

Role of shocks and mix caused by capsule defects

Observation of early shell-dopant mix in OMEGA direct-drive implosions and comparisons with radiation-hydrodynamic simulations

The effect of mix on capsule yields as a function of shell thickness and gas fill

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