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Title: Simulations of laser imprint for Nova experiments and for ignition capsules

Abstract

In direct drive inertial confinement fusion (ICF), nonuniformities in laser illumination seed ripples at the ablation front in a process called {open_quotes}imprint.{close_quotes} These nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser [Campbell {ital et al.}, Rev. Sci. Instrum. {bold 57}, 2101 (1986)] examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule pulse shape, I{congruent}10{sup 13} W/cm{sup 2}. The simulations matched most of the measurements of imprint modulation. The effect of imprint upon National Ignition Facility (NIF) direct drive ignition capsules has also been simulated. Imprint is predicted to give modulation comparable to an intrinsic surface finish of {approximately}10 nm rms. Modulation growth was examined using the Haan [Phys. Rev. A {bold 39}, 5812 (1989)] model, with linear growth factors as a function of spherical harmonic mode number obtained from an analytic dispersion relation. Ablation front amplitudes are predicted to become substantially nonlinear, so that saturation corrections are large. Direct numerical simulations of two-dimensional multimode growth were also performed. The capsule shell is predicted tomore » remain intact, which gives a basis for believing that ignition can be achieved. {copyright} {ital 1997 American Institute of Physics.}« less

Authors:
; ; ; ; ;  [1];  [2]; ;  [3]
  1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
  2. Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom)
  3. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
OSTI Identifier:
560660
Report Number(s):
CONF-961102-
Journal ID: PHPAEN; ISSN 1070-664X; TRN: 98:000743
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 4; Journal Issue: 5; Conference: Meeting of the Division of Plasma Physics of the American Physical Society, Denver, CO (United States), 11-15 Nov 1996; Other Information: PBD: May 1997
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; LASER TARGETS; ABLATION; PLASMA SIMULATION; PLASMA PRESSURE; DIRECT DRIVE LASER IMPLOSION; NOVA FACILITY; MODULATION; THERMONUCLEAR IGNITION; INERTIAL CONFINEMENT; LASER RADIATION

Citation Formats

Weber, S V, Glendinning, S G, Kalantar, D H, Key, M H, Remington, B A, Rothenberg, J E, Wolfrum, E, Verdon, C P, and Knauer, J P. Simulations of laser imprint for Nova experiments and for ignition capsules. United States: N. p., 1997. Web. doi:10.1063/1.872339.
Weber, S V, Glendinning, S G, Kalantar, D H, Key, M H, Remington, B A, Rothenberg, J E, Wolfrum, E, Verdon, C P, & Knauer, J P. Simulations of laser imprint for Nova experiments and for ignition capsules. United States. doi:10.1063/1.872339.
Weber, S V, Glendinning, S G, Kalantar, D H, Key, M H, Remington, B A, Rothenberg, J E, Wolfrum, E, Verdon, C P, and Knauer, J P. Thu . "Simulations of laser imprint for Nova experiments and for ignition capsules". United States. doi:10.1063/1.872339.
@article{osti_560660,
title = {Simulations of laser imprint for Nova experiments and for ignition capsules},
author = {Weber, S V and Glendinning, S G and Kalantar, D H and Key, M H and Remington, B A and Rothenberg, J E and Wolfrum, E and Verdon, C P and Knauer, J P},
abstractNote = {In direct drive inertial confinement fusion (ICF), nonuniformities in laser illumination seed ripples at the ablation front in a process called {open_quotes}imprint.{close_quotes} These nonuniformities grow during the capsule implosion and, if initially large enough, can penetrate the capsule shell, impede ignition, or degrade burn. Imprint has been simulated for recent experiments performed on the Nova laser [Campbell {ital et al.}, Rev. Sci. Instrum. {bold 57}, 2101 (1986)] examining a variety of beam smoothing conditions. Most used laser intensities similar to the early part of an ignition capsule pulse shape, I{congruent}10{sup 13} W/cm{sup 2}. The simulations matched most of the measurements of imprint modulation. The effect of imprint upon National Ignition Facility (NIF) direct drive ignition capsules has also been simulated. Imprint is predicted to give modulation comparable to an intrinsic surface finish of {approximately}10 nm rms. Modulation growth was examined using the Haan [Phys. Rev. A {bold 39}, 5812 (1989)] model, with linear growth factors as a function of spherical harmonic mode number obtained from an analytic dispersion relation. Ablation front amplitudes are predicted to become substantially nonlinear, so that saturation corrections are large. Direct numerical simulations of two-dimensional multimode growth were also performed. The capsule shell is predicted to remain intact, which gives a basis for believing that ignition can be achieved. {copyright} {ital 1997 American Institute of Physics.}},
doi = {10.1063/1.872339},
journal = {Physics of Plasmas},
number = 5,
volume = 4,
place = {United States},
year = {1997},
month = {5}
}