skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities

Abstract

Targets meant to achieve ignition on the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)] have been redesigned and their performance simulated. Simulations indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ignition target performance over the parameter space of ablator and fuel thickness combinations, using techniques developed by one of us (Herrmann). After the space is mapped with one-dimensional simulations, exploration of it with two-dimensional simulations quantifies the dependence of instability growth on target dimensions. Low modes and high modes grow differently for different designs, allowing a trade-off of the two regimes of growth. Significant improvement in high-mode stability can be achieved, relative to previous designs, with only insignificant increase in low-mode growth. This procedure produces capsule designs that, in simulations, tolerate several times the surface roughness that could be tolerated by capsules optimized by older more heuristic techniques. Another significant reduction in instability growth, by another factor of several, is achieved with ablators with radially varying dopant. In this type of capsule the mid-Zmore » dopant, which is needed in the ablator to minimize x-ray preheat at the ablator-ice interface, is optimally positioned within the ablator. A fabrication scenario for graded dopants already exists, using sputter coating to fabricate the ablator shell. We describe the systematics of these advances in capsule design, discuss the basis behind their improved performance, and summarize how this is affecting our plans for NIF ignition.« less

Authors:
; ; ; ; ; ; ; ; ;  [1]
  1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
Publication Date:
OSTI Identifier:
20736608
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 12; Journal Issue: 5; Other Information: DOI: 10.1063/1.1885003; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; LASER-RADIATION HEATING; PLASMA INSTABILITY; PLASMA SIMULATION; THERMONUCLEAR FUELS; THERMONUCLEAR IGNITION; US NATIONAL IGNITION FACILITY

Citation Formats

Haan, S W, Herrmann, M C, Dittrich, T R, Fetterman, A J, Marinak, M M, Munro, D H, Pollaine, S M, Salmonson, J D, Strobel, G L, and Suter, L J. Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities. United States: N. p., 2005. Web. doi:10.1063/1.1885003.
Haan, S W, Herrmann, M C, Dittrich, T R, Fetterman, A J, Marinak, M M, Munro, D H, Pollaine, S M, Salmonson, J D, Strobel, G L, & Suter, L J. Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities. United States. doi:10.1063/1.1885003.
Haan, S W, Herrmann, M C, Dittrich, T R, Fetterman, A J, Marinak, M M, Munro, D H, Pollaine, S M, Salmonson, J D, Strobel, G L, and Suter, L J. Sun . "Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities". United States. doi:10.1063/1.1885003.
@article{osti_20736608,
title = {Increasing robustness of indirect drive capsule designs against short wavelength hydrodynamic instabilities},
author = {Haan, S W and Herrmann, M C and Dittrich, T R and Fetterman, A J and Marinak, M M and Munro, D H and Pollaine, S M and Salmonson, J D and Strobel, G L and Suter, L J},
abstractNote = {Targets meant to achieve ignition on the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)] have been redesigned and their performance simulated. Simulations indicate dramatically reduced growth of short wavelength hydrodynamic instabilities, resulting from two changes in the designs. First, better optimization results from systematic mapping of the ignition target performance over the parameter space of ablator and fuel thickness combinations, using techniques developed by one of us (Herrmann). After the space is mapped with one-dimensional simulations, exploration of it with two-dimensional simulations quantifies the dependence of instability growth on target dimensions. Low modes and high modes grow differently for different designs, allowing a trade-off of the two regimes of growth. Significant improvement in high-mode stability can be achieved, relative to previous designs, with only insignificant increase in low-mode growth. This procedure produces capsule designs that, in simulations, tolerate several times the surface roughness that could be tolerated by capsules optimized by older more heuristic techniques. Another significant reduction in instability growth, by another factor of several, is achieved with ablators with radially varying dopant. In this type of capsule the mid-Z dopant, which is needed in the ablator to minimize x-ray preheat at the ablator-ice interface, is optimally positioned within the ablator. A fabrication scenario for graded dopants already exists, using sputter coating to fabricate the ablator shell. We describe the systematics of these advances in capsule design, discuss the basis behind their improved performance, and summarize how this is affecting our plans for NIF ignition.},
doi = {10.1063/1.1885003},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 12,
place = {United States},
year = {2005},
month = {5}
}