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Title: Three-dimensional simulations of ablative hydrodynamic instabilities in indirectly driven targets

To model ignition in a National Ignition Facility (NIF) capsule implosion, the authors must understand the behavior of instabilities that can cause breakup of the pellet shell. During a capsule implosion, shocks that transit the shell cause growth of perturbations at the surface or at an interface because of a Richtmyer-Meshkov type of instability. Following shock breakout, or earlier for a shaped pulse, the low-density ablated plasma accelerates the pusher, and the ablation front is Rayleigh-Taylor (RT) unstable. Ablation and finite density gradients have the effect of stabilizing the short wavelength modes. Unstable modes present on the outer surface grow and feed through to the inner surface. Once the shell encounters the rebounding shock from the capsule center, it decelerates and the inner surface becomes RT unstable. If perturbations grow large enough, pusher material mixes into the core, degrading implosion performance. Capsule designs for the NIF depend on ablative stabilization and saturation to prevent perturbations initially present on the capsule surface from growing large enough to quench ignition. Here, the authors examine the first simulations and experiments to study the effect of 3-D perturbation shape on instability growth and saturation in indirectly driven targets. The first section discusses HYDRA, themore » radiation hydrodynamics code developed for these simulations. The subsequent section examines 3-D shape effects in single-mode perturbations in planar foil simulations and experiments. A discussion of the evolution of multimode perturbations on planar foils is followed by a discussion of 3-D simulations of instability growth in Nova capsule implosions.« less
Authors:
; ;  [1]
  1. and others
Publication Date:
OSTI Identifier:
376952
Report Number(s):
UCRL-LR--105820-95
ON: DE96013181; TRN: 96:004685-0018
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jun 1996; Related Information: Is Part Of Inertial confinement fusion. 1995 ICF annual report, October 1994--September 1995; PB: 407 p.
Research Org:
Lawrence Livermore National Lab., CA (United States)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; LASER TARGETS; INDIRECT DRIVE LASER IMPLOSION; INSTABILITY; THREE-DIMENSIONAL CALCULATIONS; COMPUTERIZED SIMULATION; H CODES; PROGRESS REPORT