Scanning Microscopy


A high intensity iodine laser (1.315 μm wavelength) was used to study laser-surface damage in vacuum. A 22mm diameter laser beam containing 3.9 J of energy was focused to a 1 mm spot on an aluminum plate mounted in a vacuum chamber. The laser pulse width was 7 μs (FWHM). A copper strip mounted on a quarter circle plate 3.5 cm from the laser spot was used to collect particles ejected from the surface. A scanning electron microscope (SEM) was used to measure the size and spatial distribution of the particles collected on the copper strip. It was found that aluminum droplets were ejected from the crater formed by the laser pulse. The particle sizes ranged from 0.25 to 45 μm in diameter. The peak of the particle size distribution occurred at 1 μm diameter. The maximum spatial distribution of droplets occurred at near 47° from the normal to the target surface. Measurement of the mass lost by the target plate and the volume of aluminum removed from the craters showed that most of the aluminum ejected from the craters remained on the target surface. SEM examination of the surface adjacent to the craters showed that most of the ejected aluminum was liquid splattered around the crater. The particle size and spatial distributions are considered preliminary because droplets smaller than 0.25 μm could not be detected and the copper collector strip was examined in only six areas corresponding to six emission angles.

Included in

Life Sciences Commons