Simulation of laser to X-ray conversion features influenced by low density gold foam

Abstract

In the laser indirect-driven inertial confinement fusion, laser light is converted into X-rays by laser-plasma interactions in the hohlraum, then at the surface of the capsule the re-emission of hohlraum inner wall would drive a symmetrical radiation source to motivate implosion. It is of great importance to improve the features of laser to X-ray conversion in the hohlraum. The influence of low density gold foam on conversion features was investigated numerically with the help of one-dimensional hydrodynamics code. The numerical simulation results show that conversion efficiency increases with the decrease in gold density under the given laser condition. In particular, it can indeed have more than 19% extra conversion efficiency relatively when solid gold is replaced by gold foam of 0.1 g/cm3 density. In addition, the percentage of M-band decreases. There is an appropriate density of gold foam, at which the movement of plasma are restrained. According to the simulation results of energy balance, we get a higher radiation energy proportion when low density gold foam is selected as the target, and this is due to the decrease of kinetic energy losses compared with solid gold. Anyway, it is an effective approach to optimize the hohlraum by using low density gold foam to improve the features of laser to X-ray conversion, and these simulations would provide a scientific basis for further attempting correlative experiments.