Richtmyer - Meshkov instability in a spherical target with density variation

Abstract: The motion of unstable fluid interface due to Richtmyer - Meshkov (RM) instability incorporating with density variation has been studied in a spherical target using Lagrangian formulation. During the compression in Inertial Confinement Fusion (ICF)process, the density of deuterium - tritium (DT) fuel increases 1000 times greater than the density of gaseous DT fuel within the core of spherical target. We have extended the feature of density variation [PRA,84-Mikaelian & Lindl] in spherical geometry.Due to convergent shock impingement, the perturbed interface will be nonspherical which leads to the density variation in both radial as well as in polar angle. We have shown that the interface of perturbed surface decreases with time to reach a minimum and then kick back to gradual increase. As the perturbed radius decreases, the density increases and reaches a maxima corresponding to a minima of perturbed radius. This is the practical situation of density characteristics during implosion of ICF. The numerical results based on our analytical work show a good qualitative agreement with some experimental as well as simulation results.