Modeling hydrodynamic instabilities in inertial confinement fusion targets

In inertial confinement fusion experiments, a cold target material is accel erated by a hot, low-density plasma. The interface between the heavy and li ght materials is Rayleigh-Taylor (RT) unstable. To estimate the perturbatio n growth in accelerated targets, a postprocessor to the results of one-dime nsional codes is developed. The postprocessor is based on the sharp-boundar y model that takes into account time variation in the unperturbed state, mo de interaction of neighboring interfaces in the target, effects of spherica l convergence, and the mass ablation. The model reveals a new stabilizing e ffect of ablation for modes with wavelengths longer than the shell thicknes s. For such modes with gamma (cl)>V-a/d, the perturbation growth is reduced to eta similar to rootm(t)/m(0) x e(integral dt)' root gamma (2-kV)(V)(/(2 d))(cl)(bl)(a), wherey gamma (cl) = root kg is the classical RT growth rate of interface perturbations in the semi-infinite slab subject to gravitatio nal field g, k is the wave number, d and m(t) are the slab thickness and ma ss, and V-a and V-bl are the ablation and blowoff velocities, respectively. The perturbation evolution calculated by using the developed postprocessor is shown to be in good agreement with the results of two-dimensional hydro dynamic simulations. (C) 2000 American Institute of Physics. [S1070-664X(00 )03512-6].