Stabilization Of Rayleigh-Taylor Instability Research Articles

Stabilization of Rayleigh-Taylor instability in a non-Newtonian incompressible complex plasma

The stabilization of Rayleigh-Taylor (RT) instability is investigated in a non-Newtonian unmagnetized dusty plasma with an experimentally verified model of shear flow rate dependent viscosity. It has been found that non-Newtonian property has also a significant role in stabilization of RT instability along with velocity shear stabilization in the short wavelength regime. The effect of the non-Newtonian parameters is more profound in the higher velocity shear rate regime. A detailed study is reported on the role of non-Newtonian effect on RT instability with conventional dust fluid equations using standard numerical eigenvalue analysis.

Dynamic stabilization of Rayleigh-Taylor instability in ablation fronts

Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering the simplest possible modulations in the acceleration. Explicit analytical expressions for the instability growth rate and for the boundaries of the stability region are obtained by considering a sequence of Dirac deltas. Besides, general square waves allow for studying the effect of the driving asymmetries on the stability region as well as the optimization process. The essential role of compressibility is phenomenologically addressed in order to find the constraints it imposes on the stability region.

Strong stabilization of the Rayleigh–Taylor instability by material strength at megabar pressures

Experimental results showing significant reductions from classical in the Rayleigh–Taylor (RT) instability growth rate due to high pressure effective lattice viscosity in metal foils are presented. Stabilization of RT instability (RTI) by ablation and density gradients has been studied for decades. The regime of stabilized RTI due to material strength at high pressure is new. On the Omega Laser in the Laboratory for Laser Energetics, University of Rochester, target samples of polycrystalline vanadium are compressed and accelerated quasi-isentropically at ∼1 Mbar pressures, while maintaining the samples in the solid-state. Provided strong shocks are avoided, the higher the applied peak pressure, the higher the predicted foil strength, and hence, the higher the degree of strength stabilization of RTI. Several experiments were conducted where the amount of RT growth is measured by face-on radiography. The vanadium samples are probed by a laser driven He-α x-ray backlighter which produced 5.2 keV radiation. Comparison of the results with constitutive models for solid state strength under these conditions show that the measured RT growth is substantially lower than predictions using existing models that work well at low pressures and long time scales. High pressure, high strain rate data can be explained by the enhanced strength due to a phonon drag mechanism, creating a high effective lattice viscosity.

Coherent structures in ablatively compressed ICF targets and Rayleigh-Taylor instability

One of the major issues in laser induced inertial confinement fusion (ICF) is a stable ablative compression of spherical fusion pellets. The main impediment in achievement of this objective is Rayleigh-Taylor instability at the pellet's ablation front. Under sufficiently high acceleration this instability can grow out of noise. However, it can also arise either due to non-uniform laser intensity distribution over the pellet surface or due to pellet wall areal mass irregularity. Coherent structures in the dense target behind the ablation front can be effectively utilised for stabilisation of the Rayleigh-Taylor phenomenon. Such coherent structures in the form of a super lattice can be created by doping the pellet pusher with high atomic number (Z) micro particles. A compressed-cool pusher under laser irradiation behaves like a strongly correlated non ideal plasma when compressed to sufficiently high density such that the non ideality parameter exceeds unity. Moreover, the nonideality parameter for high Z microinclusions may exceed a critical value of 180 and as a consequence they remain in the form of intact clusters, maintaining the superlattice intact during ablative acceleration. Microhetrogeneity and its superlattice plays an important role in stabilization of Rayleigh-Taylor instability, through a variety of mechanisms.