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 »
- Publication Date:
- OSTI Identifier:
- Report Number(s):
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
- 70 PLASMA PHYSICS AND FUSION; LASER TARGETS; INDIRECT DRIVE LASER IMPLOSION; INSTABILITY; THREE-DIMENSIONAL CALCULATIONS; COMPUTERIZED SIMULATION; H CODES; PROGRESS REPORT
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