Pulsed DF Laser Effects Study.

This study of DF laser interaction with materials investigated the amount of energy coupled to targets. Large focal spot dimensions were obtained with the Boeing photo-initiated 50-1 pulsed chemical laser with a stable resonator. Effects experiments emphasized metallic targets, especially aluminum. The single pulse coupling results yielded absorbed fluence values greater than those obtained with comparable energies at 10.6 micrometer wavelength. Ambient pressure and angle of incidence were varied. Research results also showed multiple-pulse effect at DF wavelength. Multiple-pulse thermal coupling experiments with aluminum demonstrated that, after 10 shots on the same spot, the coupled fluence per pulse doubled. Because of target melting and vaporization, both the intrinsic absorptivity and the plasma enhanced coupled fluence of succeeding pulses is greatly increased. In general, the multiple pulse effect is intensity-dependent and is small at either low or high intensities. Energy deposition was tested for uniformity by measuring the rises in temperature at five locations within the focal spot with an array of thermocouples.