Generation of intense streams of metallic ions with a charge state up to 10+ in a laser ion source

The yield and the properties of Al, Au, Cu, Nb, Ni, Pb, Sn, Ta, and W ions from the plasma produced by a 0.9 J/9 ns Nd:YAG laser have been examined. Changing either the laser pulse energy or the focal spot size, the laser power density on the target surface was varied from 1×109 to about 1×1011 W/cm2, i.e., from the threshold power density for the ion generation up to the maximum laser intensities attainable with the setup used. The ion velocities (ion energies) ranged from about 2×106 to 2×107 cm/s (100 eV–10 keV) in dependence on the target element used and on the laser power density. The ion emission was peaked along the normal to the target surface; the angular distribution of ion velocities (energies) was not the same for all elements studied. Measured ion current densities ranged from 4 mA/cm2 (for Au) to 43 mA/cm2 (for Cu) at a distance of 44 cm from the target.