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Title: Ablation front rayleigh taylor dispersion curve in indirect drive

Abstract

The Rayleigh-Taylor (RT) instability, which occurs when a lower-density fluid accelerates a higher-density layer, is common in nature. At an ablation front a sharp reduction in the growth rate of the instability at short wave-lengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest wavelengths. Theoretical and numerical investigations of the ablative RT instability are numerous and differ considerably on the level of stabilization expected. We present here the results of a series of laser experiments designed to probe the roll-over and cutoff region of the ablation-front RT dispersion curve in indirect drive. Aluminum foils with imposed sinusoidal perturbations ranging in wavelength from 10 to 70 pm were ablatively accelerated with a radiation drive generated in a gold cylindrical hohlraum. A strong shock wave compresses the package followed by an {approx}2 ns period of roughly constant acceleration and the experiment is diagnosed via face-on radiography. Perturbations with wavelengths {ge} 20 {micro}m experienced substantial growth during the acceleration phase while shorter wavelengths showed a sharp drop off in overall growth. These experimental results compared favorably to calculations with a 2-D radiation-hydrodynamics code, however, the growth is significantly affected by the rippled shock launchedmore » by the drive. We performed numerical simulations to elucidate the influence of the rippled shock wave on the eventual growth of the perturbations, allowing comparisons to the analytic model developed by Betti et al. This combination of experiments, simulations and analytic modeling illustrates the qualitative simplicity yet quantitative complexity of the compressible RT instability. We have measured the Rayleigh-Taylor (RT) dispersion curve for a radiatively-driven sample in a series of experiments on the Nova laser facility. Planar aluminum foils were ablatively-accelerated and the subsequent perturbation growth was diagnosed via x-ray radiography. These measurements unambiguously map out the linear regime dispersion curve, including the observation of stabilization at short wavelengths. The data are compared favorably to two-dimensional simulations. Due to the influence of the rippled shock transit phase of the experiment, direct comparison to the ablation front RT theory of R. Betti was difficult. Instead, a numerical ''experiment'' was constructed that minimized the influence of the shock and this was compared to the Betti model showing quite good agreement.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15006505
Report Number(s):
UCRL-JC-139581
Journal ID: ISSN 1070--664X; TRN: US0400835
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Journal Volume: 8; Journal Issue: 5; Conference: 42nd Annual Meeting of the APS Division of Plasma Physics, Quebec City (CA), 10/23/2000--10/27/2000; Other Information: PBD: 17 Nov 2000
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABLATION; ACCELERATION; ALUMINIUM; BETTIS; INSTABILITY; LASERS; PHYSICS; PLASMA; PROBES; RADIATIONS; SHOCK WAVES; SIMULATION; STABILIZATION; WAVELENGTHS; X-RAY RADIOGRAPHY

Citation Formats

Budil, K S, Lasinski, B, Edwards, M J, Wan, A S, Remington, B A, Weber, S V, Glendinning, S G, Suter, L, and Stry, P. Ablation front rayleigh taylor dispersion curve in indirect drive. United States: N. p., 2000. Web. doi:10.1063/1.1356738.
Budil, K S, Lasinski, B, Edwards, M J, Wan, A S, Remington, B A, Weber, S V, Glendinning, S G, Suter, L, & Stry, P. Ablation front rayleigh taylor dispersion curve in indirect drive. United States. doi:10.1063/1.1356738.
Budil, K S, Lasinski, B, Edwards, M J, Wan, A S, Remington, B A, Weber, S V, Glendinning, S G, Suter, L, and Stry, P. Fri . "Ablation front rayleigh taylor dispersion curve in indirect drive". United States. doi:10.1063/1.1356738. https://www.osti.gov/servlets/purl/15006505.
@article{osti_15006505,
title = {Ablation front rayleigh taylor dispersion curve in indirect drive},
author = {Budil, K S and Lasinski, B and Edwards, M J and Wan, A S and Remington, B A and Weber, S V and Glendinning, S G and Suter, L and Stry, P},
abstractNote = {The Rayleigh-Taylor (RT) instability, which occurs when a lower-density fluid accelerates a higher-density layer, is common in nature. At an ablation front a sharp reduction in the growth rate of the instability at short wave-lengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest wavelengths. Theoretical and numerical investigations of the ablative RT instability are numerous and differ considerably on the level of stabilization expected. We present here the results of a series of laser experiments designed to probe the roll-over and cutoff region of the ablation-front RT dispersion curve in indirect drive. Aluminum foils with imposed sinusoidal perturbations ranging in wavelength from 10 to 70 pm were ablatively accelerated with a radiation drive generated in a gold cylindrical hohlraum. A strong shock wave compresses the package followed by an {approx}2 ns period of roughly constant acceleration and the experiment is diagnosed via face-on radiography. Perturbations with wavelengths {ge} 20 {micro}m experienced substantial growth during the acceleration phase while shorter wavelengths showed a sharp drop off in overall growth. These experimental results compared favorably to calculations with a 2-D radiation-hydrodynamics code, however, the growth is significantly affected by the rippled shock launched by the drive. We performed numerical simulations to elucidate the influence of the rippled shock wave on the eventual growth of the perturbations, allowing comparisons to the analytic model developed by Betti et al. This combination of experiments, simulations and analytic modeling illustrates the qualitative simplicity yet quantitative complexity of the compressible RT instability. We have measured the Rayleigh-Taylor (RT) dispersion curve for a radiatively-driven sample in a series of experiments on the Nova laser facility. Planar aluminum foils were ablatively-accelerated and the subsequent perturbation growth was diagnosed via x-ray radiography. These measurements unambiguously map out the linear regime dispersion curve, including the observation of stabilization at short wavelengths. The data are compared favorably to two-dimensional simulations. Due to the influence of the rippled shock transit phase of the experiment, direct comparison to the ablation front RT theory of R. Betti was difficult. Instead, a numerical ''experiment'' was constructed that minimized the influence of the shock and this was compared to the Betti model showing quite good agreement.},
doi = {10.1063/1.1356738},
journal = {},
number = 5,
volume = 8,
place = {United States},
year = {Fri Nov 17 00:00:00 EST 2000},
month = {Fri Nov 17 00:00:00 EST 2000}
}

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