Ion acceleration enhancement in laser-generated plasmas by metallic doped hydrogenated polymers
Laser-generated plasmas in vacuum were obtained by ablating hydrogenated polymers at the Physics Department of the University of Messina and at the PALS Laboratory in Prague. In the first case a 3 ns, 532 nm Nd:Yag laser, at 10^10 W/cm^2 intensity was employed. In the second case a 300 ps, 438 nm iodine laser, at 5x10^14 W/cm^2 intensity was employed. Different ion collectors were used in a time-of-flight configuration to monitor the ejected ions from the plasma at different angles with respect to the direction normal to the target surface. Measurements demonstrated that the mean ion velocity, directed orthogonally to the target surface, increases for ablation of polymers doped with metallic elements with respect to the nondoped one. The possible mechanism explaining the results can be found in the different electron density of the plasma, due to the higher number of electrons coming from the doping elements. This charge enhancement increases the equivalent ion voltage acceleration, i.e. the electric field generated in the non-equilibrium plasma placed in front of the ablated target surface.