Development of an optically recording velocity interferometer system for laser induced shock waves measurements

An optically recording velocity interferometer system, ORVIS, was developed for measurements of the time evolution of the free surface and the particle velocity in laser induced shock waves experiments. This system produces interference fringe shifts which are proportional to the Doppler shift of a laser beam reflected from the moving surface. These fringe shifts are recorded with a high speed electronic streak camera, which has a 70 ps time resolution. Using this method, the free surface velocity was measured with an accuracy better than 5% and the pressure in laser shocked aluminum targets was calculated. Shock waves of order of hundreds of kilobars are produced by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 5 ns (FWHM) and energy in the range (30–50) J, focused to spots diameters in the range (200–1000) μm. The dynamic spall strength reported here for Al is (14.47±1.45) kbar for a strain rate of ε̇∼8×106s−1, consistent with studies performed with other methods.