Modeling of laser-driven shocks into porous graphite

This paper presents experiments of laser-driven shocks into a commercial grade of porous graphite. Intensities of about 3~GW.cm$^{-2}$ led to pressures close to 3~GPa on the front surfaces of the 0.5~mm samples. The rear surface velocities, recorded by a Velocity Interferometer System (VISAR), ranged from 250 to 325 m.s$^{-1}$. Two classical models for porous materials are discussed. The first one uses plates of dense graphite spaced out in order to obtain the correct average density. The second one models a continuous material and includes an experimental compaction curve of our porous graphite. They were implemented into hydrocodes and both gave quite correct maximum free surface velocities and shock break-out instants. Nevertheless, the continuous representation appeared to be more efficient to reproduce the experimental free surface velocity ramp. Discussions on the laser-matter interaction modeling are also provided. Finally, a protocol for the simulation of future laser experiments is proposed.