2D characterization of the pressure generated by an intense laser pulse on an aluminum target

High intensity lasers are a very powerful tool to study the mechanical properties of materials, such as equation of state, or dynamic fracture. In the first case, laser experiments are usualy designed so as to allow 1D interpretation of the measurements. However, as regards the characterization of materials strength, it can be useful to take advantage of 2D effects that are due to the finite size of the laser focal spot, for instance in cratering experiments on thick samples. In this paper, we present an experimental study of the 2D mechanical loading generated by the interaction of a high power laser (40J, 100ns) with aluminum targets. The focal spot diameter is approximately 0.22mm. Under such conditions, the pressure generated on the sample by the ablation process can reach 8 GPa. In our experiments, targets were 0.2mm thick aluminum plates, and a VISAR was used to record the free surface velocity at various positions off the symmetry axis. The radial dependance of the mechanical loading was then deduced from these measurements and used to simulate cratering experiments on thick samples. Some differences are observed and discussed.