Computational model for a low-temperature laser-plasma driver for shock-processing of metals and comparison to experimental data

Few-joule table-top lasers can generate pressures up to the 100 kbar range in solid materials by propagating a low-intensity beam through a transparent dielectric, which confines the ablation pressure, onto an ablation layer in contact with the material of interest. This technique has application in studies of material dynamic behavior and material processing. Development and application of physically based models of this process have lagged experiment. In this article the particulars of a detailed computational model incorporated into a two-dimensional radiationhydrodynamics code are presented. The model accounts for the initial absorption onto a metal surface, low-intensity photoionization absorption in neutral vapor, collisional ionization, recombination, dielectric breakdown, band gap collapse, electron conductivity, thermal transport, and constitutive properties of the materials. The model shows that most of the laser energy is absorbed in the dielectric tamper, not the ablator. Good agreement is found between simulated and measured pressure histories for materials irradiated with several tens of joules using a single-beam neodymium-glass laser at the Lawrence Livermore National Laboratory