MEASUREMENT OF EXTINCTION COEFFICIENTS OF LASER-PRODUCED ALUMINUM PLUMES

Radial spectral intensities (0.632 mum) were measured using a He:Ne pr obe laser scanning an aluminum plume formed by Nd:glass laser irradiat ion of a target surface. Furthermore, techniques were developed to mea sure the radial distributions of the extinction coefficients in an axi symmetric, laser-produced aluminum plume. The techniques developed all ow for measurements of these distributions as functions of time, wavel ength, and elevation above the aluminum target. The extinction coeffic ients determine the ability of the plasma to attenuate incident laser radiation. The extinction coefficient distribution was determined by s canning a He:Ne probe laser through the plume and converting line-of-s ight measurements to a radial distribution. Results indicate that the aluminum plume is optically thin in the first 80 mus after formation a nd that the radial extinction coefficient profile has a Gaussian distr ibution.