Influences of plasma shielding and rarefaction wave on impulse coupling coefficient

The relationship between the impulse coupling coefficient and the distance of the target from focus at different incident laser energy, and the relationship between impulse coupling coefficient and laser spot diameter at different incident laser intensity were studied by applying Nd:YAG laser pulse on the Al(Cu) target. The experiments show that the target position corresponding to the peak impulse coupling coefficient moves towards to the lens with the increase of the laser energy, and the increase of the optimum intensity is small. These prove that the plasma shielding induces decreases impulse coupling coefficient to decrease after the peak value. On the other hand impulse coupling coefficient increases with the increase of the laser spot diameter in a linear way at the same incident la