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Title: Test of Thermal Transport Models through Dynamic Overpressure Stabilization of Ablation-Front Perturbation Growth in Laser-Driven CH Foils

Abstract

Heat-flow-induced dynamic overpressure at the perturbed ablation front of an ICF target can stabilize the ablative Richtmyer/Meshkov-like instability and mitigate the subsequent ablative Rayleigh/Taylor (RT) instability. A series of experiments was performed on the OMEGA laser to quantify the dynamic overpressure stabilization during the shock transit. Analysis of the experimental data using hydrocode simulations shows that the observed oscillatory evolution of the ablation-front perturbations depends on Dc, the size of the thermal conduction zone, and the fluid velocity in the blowoff region Vbl that are sensitive to the thermal transport model used. We show that the simulations match the experiment well when the time dependence of the heat-flux inhibition is taken into account using a recently developed nonlocal heat transport model.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Laboratory for Laser Energetics, University of Rochester, Rochester, NY
Sponsoring Org.:
USDOE
OSTI Identifier:
878460
Report Number(s):
DOE/SF/19460-660
1621; 2005-159
DOE Contract Number:
FC52-92SF19460
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 96
Country of Publication:
United States
Language:
English

Citation Formats

Gotchev, O.V., Goncharov, V.N., Knauer, J.P., Boehly, T.R., Collins, T.J.B., Epstein, R., Jaanimagi, P.A., and Meyerhofer, D.D.. Test of Thermal Transport Models through Dynamic Overpressure Stabilization of Ablation-Front Perturbation Growth in Laser-Driven CH Foils. United States: N. p., 2006. Web. doi:10.1103/PhysRevLett.96.115005.
Gotchev, O.V., Goncharov, V.N., Knauer, J.P., Boehly, T.R., Collins, T.J.B., Epstein, R., Jaanimagi, P.A., & Meyerhofer, D.D.. Test of Thermal Transport Models through Dynamic Overpressure Stabilization of Ablation-Front Perturbation Growth in Laser-Driven CH Foils. United States. doi:10.1103/PhysRevLett.96.115005.
Gotchev, O.V., Goncharov, V.N., Knauer, J.P., Boehly, T.R., Collins, T.J.B., Epstein, R., Jaanimagi, P.A., and Meyerhofer, D.D.. Fri . "Test of Thermal Transport Models through Dynamic Overpressure Stabilization of Ablation-Front Perturbation Growth in Laser-Driven CH Foils". United States. doi:10.1103/PhysRevLett.96.115005.
@article{osti_878460,
title = {Test of Thermal Transport Models through Dynamic Overpressure Stabilization of Ablation-Front Perturbation Growth in Laser-Driven CH Foils},
author = {Gotchev, O.V. and Goncharov, V.N. and Knauer, J.P. and Boehly, T.R. and Collins, T.J.B. and Epstein, R. and Jaanimagi, P.A. and Meyerhofer, D.D.},
abstractNote = {Heat-flow-induced dynamic overpressure at the perturbed ablation front of an ICF target can stabilize the ablative Richtmyer/Meshkov-like instability and mitigate the subsequent ablative Rayleigh/Taylor (RT) instability. A series of experiments was performed on the OMEGA laser to quantify the dynamic overpressure stabilization during the shock transit. Analysis of the experimental data using hydrocode simulations shows that the observed oscillatory evolution of the ablation-front perturbations depends on Dc, the size of the thermal conduction zone, and the fluid velocity in the blowoff region Vbl that are sensitive to the thermal transport model used. We show that the simulations match the experiment well when the time dependence of the heat-flux inhibition is taken into account using a recently developed nonlocal heat transport model.},
doi = {10.1103/PhysRevLett.96.115005},
journal = {Physical Review Letters},
number = ,
volume = 96,
place = {United States},
year = {Fri Mar 24 00:00:00 EST 2006},
month = {Fri Mar 24 00:00:00 EST 2006}
}
  • Heat-flow-induced dynamic overpressure at the perturbed ablation front of an inertial confinement fusion target can stabilize the ablative Richtmyer-Meshkov-like instability and mitigate the subsequent ablative Rayleigh-Taylor (RT) instability. A series of experiments was performed on the OMEGA laser to quantify the dynamic overpressure stabilization during the shock transit. Analysis of the experimental data using hydrocode simulations shows that the observed oscillatory evolution of the ablation-front perturbations depends on D{sub c}, the size of the thermal conduction zone, and the fluid velocity in the blowoff region V{sub bl} that are sensitive to the thermal transport model used. We show that themore » simulations match the experiment well when the time dependence of the heat-flux inhibition is taken into account using a recently developed nonlocal heat-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)].« less
  • Aluminum foils 1--75 ..mu..m thick were irradiated by 500-psec Nd-glass laser pulses with intensities 6 x 10/sup 12/ to 10/sup 14/ W/cm/sup 2/. The reflected and transmitted light and the produced x rays were measured using PIN photodiodes and crystal spectrometers. Two torsion pendula were used to measure the target and the plasma momenta. Both measurements are consistent with a simple hydrodynamic model. We obtain plasma pressures in the range 1.5--13 Mbars, shock-wave velocities between 0.9 x 10/sup 6/ and 2.6 x 10/sup 6/ cm/sec, penetration depths of the ablation surface in the domain of 3--10 ..mu..m for laser intensitiesmore » in the range 6 x 10/sup 12/ to 10/sup 14/ W/cm/sup 2/. The burn-through times (i.e., the times that a hole is opened in the foil) for foils 25, 50, and 75 ..mu..m thick are measured to be 8 +- 5, 18 +- 5, and 25 +- 5 nsec, respectively.« less
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  • Spatial profile of ablation front is observed under the irradiation of spatially modulated 0.27-..mu..m laser beam. Propagation depth of the ablation front is derived by means of various methods which detect x-ray radiation from aluminum substrates overcoated with polyethylene layers of different thicknesses. A higher mass ablation rate is observed for the UV laser than the longer wavelength lasers. However, observation with an x-ray television camera shows that the spatial nonuniformity in the laser beam is projected on the ablation front surface without substantial smoothing.
  • A technique to provide a self-consistent determination of Rayleigh-Taylor (RT) growth rates along with ablation-front density from measured optical-depth growth of preimposed, two-dimensional sinusoidal modulations is presented. The RT growth rates of ablation-front amplitude along with ablation-front density were determined using the optical-depth modulation ratios of the fundamental wavelength to the second-harmonic amplitudes.