Modeling hydrodynamic instabilities in inertial confinement fusion targets

In inertial confinement fusion experiments, a cold target material is accelerated by a hot, low-density plasma. The interface between the heavy and light materials is Rayleigh-Taylor (RT) unstable. To estimate the perturbation growth in accelerated targets, a postprocessor to the results of one-dimensional codes is developed. The postprocessor is based on the sharp-boundary model that takes into account time variation in the unperturbed state, mode interaction of neighboring interfaces in the target, effects of spherical convergence, and the mass ablation. The model reveals a new stabilizing effect of ablation for modes with wavelengths longer than the shell thickness. 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)(/(2d))(cl)(bl)(a), wherey gamma (cl) = root kg is the classical RT growth rate of interface perturbations in the semi-infinite slab subject to gravitational field g, k is the wave number, d and m(t) are the slab thickness and mass, 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 hydrodynamic simulations. (C) 2000 American Institute of Physics. [S1070-664X(00)03512-6].