Laser-driven spall experiments in ductile materials in order to characterize Johnson fracture model constants
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.
We argue that in the measured $p_T$ domain of RHIC, collisional rather than the radiative energy loss is the dominant mechanism for jet quenching. Accordingly we calculate nuclear suppression factor for light hadrons by taking only the elastic energy loss in sharp contrast with the previous calculations where only the radiative loss are considered.