Erosion plume characteristics determination in ablation of metallic copper, niobium and tantalum targets

On irradiation of metallic targets from niobium and tantalum with excimer XeCl laser (308 nm) in vacuum the UV and visible spectra of erosion plume were obtained. The erosion plume after ablation of copper, niobium and tantalum targets was studied using Langmuir probe. The ion and electron probe currents were obtained in the range from 0.2 to 2.2 J/cm(-2) of energy densities at the target with probe-to-target separations from 10 to 133 mm. Multimodal distributions of ions by scatter velocities have been revealed. The spatial and temporal dependencies of electron probe currents were obtained in real time. The electron temperature of different plume regions was determined from a series of I-U characteristics taken at different distances between probe and copper or tantalum target. It was established that the plume electron temperature is non-uniform and has a maximum value in front of the plume. The acceleration of tantalum ions on plume irradiation with cw CO2 laser recorded. The increase in ions energy from 25 to 50 eV was observed. The emission optical spectra were used in studying the plume qualitative composition. The velocities of atom and ion scatter were measured by the time-of-flight method from the emission optical spectra.