An experimental study of recombination in a laser-produced plasma

Abstract

Ion kinetic energies up to approximately=40 keV measured at a large range of distances from the target (8 mm to 2.18 m) for a laser-produced plasma created by a neodymium laser of pulse length 4 ns focused to an intensity approximately 10¹⁶ Wm^-2 onto a solid carbon slab are presented. With increasing distance from the target, an increase in average ion energy and a decrease in the number of ions detected for each ion species is observed up to a distance of 1.45 m from the target, while at longer distances (>1.45 m) the average ion energy and number of ions detected remain approximately constant with increasing distance from the target. The results show that recombination is important in determining the ion energy spectra observed in laser-produced plasma studies, but that there are also (higher energy) ions which are 'frozen' in high charge states and do not recombine even by the time they have travelled long distances from the target.