Numerical study of the impedance mismatch effect in laser-irradiated layered targets

Abstract

The effect of impedance mismatch on shock-pressure enhancement in laser-irradiated layered targets has been investigated by numerical simulation of the entire time history of shock generation. The model is a simple, one-dimensional, single-temperature Lagrangian hydrodynamic code incorporating a simplified laser-absorption model and an equation of state suitable to describe the thermodynamic state of matter in a wide range of density and temperature. Effects of change in layer materials and other experimental parameters on the attainable shock pressure and compression have been studied. From an exhaustive study of such targets, it is found that it is possible to enhance the attainable values of compression (ρ /ρ ₀)and shock pressure with a given laser pulse by suitable optimization of the target. A pressure of more than 60 Mbar can be generated with a 10¹⁴ W/cm², 300-ps rise-time laser pulse in such targets. In order to generalize the applicability of the results, within existing experimental uncertainties of measurements, and facilitate a suitable target design for any laser system, simple scaling laws are obtained in terms of parameters like intensity and rise time of the laser pulse.