DEVELOPMENT OF AN OPTICALLY RECORDING VELOCITY INTERFEROMETER SYSTEM FOR LASER-INDUCED SHOCK-WAVES MEASUREMENTS

An optically recording velocity interferometer system, ORVIS, was deve loped for measurements of the time evolution of the free surface and t he particle velocity in laser induced shock waves experiments. This sy stem produces interference fringe shifts which are proportional to the Doppler shift of a laser beam reflected from the moving surface. Thes e fringe shifts are recorded with a high speed electronic streak camer a, which has a 70 ps time resolution, Using this method, the free surf ace velocity was measured with an accuracy better than 5% and the pres sure in laser shocked aluminum targets was calculated. Shock waves of order of hundreds of kilobars are produced by a Nd:YAG laser system wi th a wavelength of 1.06 mu m, pulse width of 5 ns (FWHM) and energy in the range (30-50) J, focused to spots diameters in the range (200-100 0) mu m. The dynamic spall strength reported here for Al is (14.47+/-1 .45) kbar for a strain rate of epsilon over dot similar to 8x10(6)s(-1 ), consistent with studies performed with other methods. (C) 1996 Amer ican Institute of Physics.