A simple model for the determination of laser ablation pressure from shock transit time measurements

Summary form only given, as follows. A single beam of the Nova laser, spatially uniform in 2/spl omega//sub o/ intensity due to smoothing by a random phase plate and spectral dispersion, was used to produce large diameter (1-mm) highly planar shocks in flat aluminum targets by direct illumination. Targets were constructed so that a range of thicknesses could be illuminated simultaneously, thus allowing shock transit time measurements by observing rear-side break-out with an imaging optical streak camera. Targets were illuminated by typical energies of 3-5 kJ with both 1-ns flat top pulses and 2.5-ns temporally shaped pulses having a 1.0-ns low-intensity foot followed by a higher-intensity main pulse. A simple model has been developed which uses the Hugoniot equations and the SESAME EOS table to relate these measurements to the laser ablation pressure. Results of the model have been compared to computer simulations using the 1D Lagrangian radiation-hydrodynamics code HYADES.