Numerical evaluation of the impact of laser preheat on interface structure and instability

This paper presents a computational study of the impact of preheating, in advance of shock heating, on a structured interface and on the subsequent postshock instability evolution. The study was performed by applying a method, described previously, of evaluating radiative effects using a multidimensional, front-tracking hydrodynamic code with input from a one-dimensional, radiation-hydrodynamic code. The method is general and could be applied to a range of laser-driven shock experiments. Results of simulations are shown for both high and low levels of preheat, conducted using a robust front-tracking algorithm in the presence of a radiation energy source. In the low-preheat case, which represents the minimum to be anticipated in laboratory experiments, some impact of preheat on both preshock conditions and postshock evolution are observed. In the high-preheat case, which represents one potential result of preheating by increased radiation and/or energetic electrons, the preheat alters the spectral content of the interface structure. In this case, before the shock reaches the interface, higher-order harmonic modes are induced, the interface position is shifted, and the perturbation amplitude is reduced. Furthermore, the postshock evolution of the interface is affected by the amount of preheat and by whether radiative heating after the laser pulse is also included. Such a numerical assessment of preheating can be important to the design and analysis of laboratory experiments. The initial conditions for the interaction of any shock wave with structures in the target may be altered by the presence of preheating. This poses a challenge to the laser experimental study of fluid mixing. Numerical simulations can serve as a useful tool to guide decisions regarding control and/or measurement of this effect. © 2007 American Institute of Physics. DOI: 10.1063/1.2739453