We describe laser-driven spall experiments on aluminum, tantalum, steel and gold targets. The free-surface velocity is measured by using a VISAR diagnostic and is compared with numerical simulations at early spallation stage based on the Johnson fracture model. For each material, we first launch one-dimensional simulations with different values of the model parameters and determine the ones which reproduce correctly the experimental data. Then we use two-dimensional simulations to take into account spatial inhomogeneity of the loading pressure over the laser spot. We show non planar ejected spalls which are in agreement with experimental results. We finally study the fragmentation of thin targets and show differences in material behavior for steel in comparison to gold, tantalum and aluminum.

Although shock-induced fracture and fragmentation of materials at low temperatures are issues of considerable interest for many applications, such as the protection from hypervelocity impacts in outer space or the ongoing development of high energy laser facilities aiming at inertial confinement fusion, little data can be found on the subject yet. In this paper, laser driven shock experiments are performed on gold and aluminum samples at both ambient and cryogenic (down to about 30 K) temperatures. Complementary techniques including transverse optical shadowgraphy, time-resolved velocity measurements, and post-recovery analyses are combined to assess the effects of target temperature upon the processes of microjetting, spallation, and dynamic punching, which are expected to govern fragments generation and ejection. The results indicate that cryogenic temperature tends to reduce the resistance to tensile and shear stresses, promotes brittle fracture, and leads to slightly higher fragments ejection velocities.