HIGH-INTENSITY ULTRAVIOLET-LASER INTERACTION WITH A METALLIC FILAMENT

Results of research conducted on interaction of high-intensity ultraviolet pulsed KrF laser radiation with a metallic filament in atmospheric air are reported. Experimental results are presented on the time dependent material ejection dynamics associated with pulsed single shot focused excimer laser beams interacting with a small diameter wire. Copper wire 75-mu-m in diameter was illuminated with a KrF (lambda = 248 nm, pulse duration = 17 ns full width at half-maximum) excimer laser at an irradiance of 80 GW/cm2. Interaction dynamics were recorded using both real-time and double-strobed ultraviolet laser imaging techniques. Temporal and spatial evolutions of both vaporized and molten material are reported. Material observed, during two-dimensional shadow imaging, on the side opposite the incident beam (shadow side) was shown to originate from the front ablating surface without spallation of material on the shadow surface. Several spatial material emission velocities are reported utilizing two different imaging techniques. A maximum velocity of 1500 m/s was obtained for material ejected in a direction toward the ablating laser.