Characterization of laser-driven shocks of high intensity using piezoelectric polymers

Abstract

Piezoelectric elements made of polyvinylidene-fluoride-trifluoroethylene copolymer P(VDF/TrFE) have been used to measure the pressure induced on the rear surface of metallic foils irradiated by infra-red laser pulses of 1.5 ns duration, with intensities up to 3 TW/cm2. The application of such piezoelectric materials under those conditions is new, and a special effort has been made for their improvement and characterization under plate impact loading. Then, the laser experiments have been carried out. First, peak pressures of 0.5–7.5 GPa transmitted in the copolymer have been derived from the peak voltage measured at each shot, using simple assumptions. Next, a more accurate analysis of the data, involving computer simulations, has provided the pressure profiles characterizing the laser shocks driven on the front surface of the targets, over a wide range of laser intensities. Peak pressures of 7–60 GPa on the irradiated surface have been inferred from that analysis. The results have been compared to values obtained from a classical scaling law on one hand, and to predictions of a laser-matter interaction simulation code on the other hand. An overall coherence has been obtained, despite some discrepancies that have been discussed.