Concept Development for Astrophysically Relevant Turbulence on NIF

Abstract

(a) Abstract: We carried out the research proposed in the proposal and developed a specific concept for the generation of fully developed Rayleigh-Taylor turbulence on NIF. Under this contract we carried out the design study that we proposed. We demonstrated that NIF is capable of producing self-similar turbulence resulting from the Rayleigh-Taylor instability. Our detailed study shows that NIF can in fact produce a more-developed turbulent state than we estimated in the proposal. Thus, NIF can go far beyond any previous experiment in the generation of a hydrodynamic state that can be described as fully developed turbulence.To accomplish our study, we first assessed what sort of experimental system NIF was capable of driving, for modest values of the laser parameters. We developed a desgin for a specific target that could produce Rayliegh-Taylor turbulentce. We then performed hydrodynamic simulations of of this system. We analyzed the results of these simulations to determine the likely evolution of the turbulence in a NIF experiment.The results of our work are discussed in the following, which is a draft paper for publication. We are now undertaking multidimensional simulations, which will also be included in the paper before it is submitted. 1A preliminary design of a two-dimensional Rayleigh-Taylor experiment on NIF AbstractAn preliminary design of an experiment meant to investigate the evolution of multimode Rayleigh-Taylor instability (RT) is presented. This experiment is intended to provide a direct measurement of the two-dimensional bubble front evolution in the hydrodynamic regime. RT growth for the proposed design has been analyzed using one-dimensional direct numerical simulations in HYADES, and a self-similar behavior model. The proposed design assures a significant bubble merging process (∼ 3-4 bubble merger generations), bringing the bubble front to the self-similar stage. The design takes advantage of the National Ignition Facility (NIF) capabilities to provide a large enough laser spot area (∼0.5-1 cm 2 ), along with a low enough drive, so preheat effects remain reasonably small.