High-Speed Laser-Launched Flyer Impacts Studied with Ultrafast Photography and Velocimetry

Abstract

Pulsed lasers can launch thin metal foils at km s−1, but for precision measurements in shock compression science and shock wave spectroscopy, where one-dimensional shock compression is vital, flyer plate impacts with targets must have a high degree of flatness and minimal tilt, and the flyer speeds and impact times at the target must be highly reproducible. We have developed an apparatus that combines ultrafast stroboscopic optical microscopy with photon Doppler velocimetry to study impacts of laser-launched Al and Cu flyer plates with flat, transparent glass targets. The flyer plates were 0.5 mm in diameter, and ranged from 12 to 100 μm thick, with flyer speeds up to 6.25 km s−1. The velocity variations over 30–60 launches from the same flyer plate optic can be as low as 0.6 %, and the impact time variations can be as low as 0.8 ns. Stroboscopic image streams (reconstructed movies) show uniform, flat impacts with a glass target. These stroboscopic images can be used to estimate the tilt in the flyer-target impact to be <1mrad.