DEBRIS FROM HIGH-ASPECT-RATIO RECTANGULAR FOCUSED LASER IRRADIATION ON A TAPE TARGET SURFACE IN AN X-RAY LASER SYSTEM

This study measures the distribution of debris ejected from an aluminu m tape target subjected to laser irradiation. The irradiation area is rectangular with a high aspect ratio of 67. The power density of the l aser beam is 8 x 10(10) w/cm(2) at the irradiation surface. The ejecte d debris is collected on a plane parallel to the target surface. The a ngular distribution of debris thickness in the direction parallel to t he longer side of the irradiation area is cos(60) theta(h). Similarly, the angular distribution of debris thickness in the direction paralle l to the shorter side of the irradiation area is cos(5) theta(v), wher e the angles theta(h), and theta(v) are deviations from the irradiatio n surface normal in the horizontal and vertical directions, respective ly. An additional feature is the sacrificial film feed mechanism desig ned to shield the laser beam entrance window from debris deposition. B ased on the angular distribution of debris thickness, the film feed ra te is adjusted to ensure delivery of the required beam energy at the t arget surface.