Richtmyer-Meshkov-like instabilities and early-time perturbation growth inlaser targets and Z-pinch loads

The classical Richtmyer-Meshkov (RM) instability develops when a planar sho ck wave interacts with a corrugated interface between two different fluids. A larger family of so-called RM-like hydrodynamic interfacial instabilitie s is discussed. All of these feature a perturbation growth at an interface, which is driven mainly by vorticity, either initially deposited at the int erface or supplied by external sources. The inertial confinement fusion rel evant physical conditions that give rise to the RM-like instabilities range from the early-time phase of conventional ablative laser acceleration to c ollisions of plasma shells (like components of nested-wire-arrays, double-g as-puff Z-pinch loads, supernovae ejecta and interstellar gas). In the lase r ablation case, numerous additional factors are involved: the mass flow th rough the front, thermal conduction in the corona, and an external perturba tion drive (laser imprint), which leads to a full stabilization of perturba tion growth. In contrast with the classical RM case, mass perturbations can exhibit decaying oscillations rather than a linear growth. It is shown how the early-time perturbation behavior could be controlled by tailoring the density profile of a laser target or a Z-pinch load, to diminish the total mass perturbation seed for the Rayleigh-Taylor instability development. (C) 2000 American Institute of Physics. [S1070-664X(00)93305-6].