Laser-Initiated Diverging and Converging Spherical Blast Waves

In a study that is preliminary to a spherical pinch experiment, attention is focused on divergent and convergent shock waves. An intense laser beam is used to initiate a gas breakdown to generate a divergent shock wave at the center of a spherical cell; the temporal evolution of the shock front is tracked by holographic interferometry. A convergent shock wave is produced from the laser-induced evaporation of a metallic layer present on the internal surface of a hemi-spherical cell; a framing camera is employed to obtain streak pictures. Theoretical models are used to interpret the experimental results.