Rayleigh–Taylor instability in ion beam driven ablation fronts

Abstract

A physical model for the linear stage of Rayleigh–Taylor instability in ablation fronts is presented. The model allows for direct physical interpretation and for retrieving the well known results for the instability growth rate in ablation fronts driven by thermal diffusion. The model is applied to ablation fronts directly driven by intense ion beams and the instability growth rate is found. We show that ablation by itself still provides a mechanism for growth rate reduction but the cutoff wave number above which the front becomes stable, does no exist in ion beam driven ablation fronts.

Vibration waveform effects on dynamic stabilization of ablative Rayleigh-Taylor instability

“…12,13 These experiments are of relevance for applications to ICF because of the close analogies existing between the viscosity and surface tension in Newtonian fluids, and the effects of the mass ablation rate on the evolution of the RTI in an ablation front. 14 Most of the former studies on dynamic stabilization of RTI have considered a sinusoidal driving of the interface requiring rather complicated numerical calculations in order to find the region of stability. Such an approach makes very difficult to obtain the similarity relationships that rules the problem and that are necessary for the design and interpretation of experiments.…”

Dynamic stabilization of Rayleigh-Taylor instability in ablation fronts

“…The information regarding the density profiles at both sides of the front is incorporated by considering the self-consistent density jump r D = 1 / 2 , with 1 and 2 taken as the densities at a distance k −1 of the interface. Thus, we can get the equation of motion of the interface due to the instability [3,6,8]:…”

“…is the Atwood number, v 2 is the ablation velocity, and 0 is the fraction of the energy that is transported up to the front by thermal conduction [3]. The density jump r D is given by the mechanism of energy transport and, by taking r D 1, we can write r D ≈ (nkL 2 ) n , where L 2 is the characteristic length of the density/temperature gradient in the corona region (y > 0) close to the front.…”

“…[2,3,[6][7][8]. The interface is placed at y = (x, t) and separates two fluids of densities 2 and 1 < 2 , ahead and behind the front, respectively.…”

“…Here, we present a study for the particular case of an ablation front directly driven by ion beams for which DS can be of special interest [3][4][5]. However, application of the methods presented here to ablation fronts driven by thermal diffusion are straightforward.…”