Generation of Ions and X-rays from a Cu Target by Irradiation of High-power Femtosecond Laser

Abstract

We investigated ions and X-rays generated from a Cu target by irradiation of a femtosecond laser pulse at power densities above 10¹⁵ W/cm². The kinetic energy of positive ions was measured by a charge collector. The time-of-flight spectra showed multi-peaked structures. The ion energy of faster peak was estimated to be 4.6 keV at power density of 1×10¹⁷ W/cm². This ion energy increased with an increase in the laser energy. The ion energy of slower peak was estimated to be about 20 eV and independent of the laser energy. Generated X-rays were detected as hard X-rays in the range of 3-30 keV and as CuKα line diffracted from Si(111). Both intensities increased with an increase in the laser energy.