A 1D Analysis of Direct and Indirect Drive Target Performance for Planar Hydrodynamics Experiments on the NIF

Edwards, M.J.

Lawrence Livermore National Laboratory

关键词: 99 General And Miscellaneous//Mathematics, Computing, And Information Science;    Ablation;    Targets;    Equations Of State;    Performance;   

DOI  :  10.2172/793580
RP-ID  :  UCRL-ID-139831
RP-ID  :  W-7405-Eng-48
RP-ID  :  793580

美国|英语

来源: UNT Digital Library

【 摘 要 】

The 1D performance of laser or X-ray driven targets to study phenomena such as the Richtmyer-Meshkov instability in a single, steady shock, step down in density system has been described by a simple model based on 1D hydrodynamics. It is shown that the distance the interface travels under constant velocity conditions is a multiple of the separation between the ablation and shock front, and that this multiple depends on the density ratio at the interface, and the equations of states of the two materials. The model is applied to NIF with the aid of 1D hydrocode simulations to predict the ablation-shock separation. It is found that if adequate interface planarity can be maintained over an experimental length equal to the focal spot diameter, direct drive may out-perform indirect drive by up to {approx} factor 2 at the same pulse length and typically {ge} 2 at the same ablation pressure. This depends on the ability to control 2D effects in the directly driven targets (critically), and on the optimum hohlraum performance achievable for these experiments, rather than the achievable performance used for the study. It is predicted that several mm of constant velocity interface travel are potentially achievable on NIF, and that this is only weakly dependent on the available energy. The 1D model and its application are described. Uncertainties surrounding the predictions are discussed, and means to resolve them outlined.