Optical windows as materials for high-speed shock wave detectors

Abstract

Experimental studies of high-velocity (1-4 km/s) impacts of laser-launched flyer plates with polycrystalline, glassy or polymer windows were performed, with the intent of understanding and assessing the use of optical windows as high-speed solid-state shock wave detector materials. The problem is that the detector material undergoes radical physical transformations during the measurement. Here we present a simplified model where the detector material transformations are described as velocity and time dependent changes in shock impedance. The window materials were used to study the detonation shock produced by nitromethane, which is about 20 GPa and 10 ns. Reference experiments producing shocks in this pressure and duration range characterized how the shock impedances changed with impact velocity and shock duration. Sapphire, CaF2 and LiF windows had the fastest response to the detonation shocks, while the polymer windows had a sluggish response. Pyrex and BK7 were the best of the glassy windows.