Proton emission from laser - generated plasmas at different intensities

Proton acceleration from laser-generated plasma is carried out at intensities ranging between 1010 and 1019 W/cm2, by using ns, ps and fs laser systems. The high energy density transferred from the pulsed laser beam into the solid target generates ionized species released in vacuum from the solid surface. Fast electrons followed by slower ions build up a double-layer and a consequent electric field, which is responsible for the ion acceleration mainly along the target-normal. Polymeric targets containing nanostructures (or metallic species) with high laser absorbing capacity, and metallic hydrates (or H-enriched metals), permit to increase the plasma temperature and density, thus to improve the proton beam energy and current. Thick targets and low laser intensities, operating in repetitive pulse, allows to generate high currents of low energy protons. On the other hand, through the use of thin targets and high laser intensities enabled the generation of high proton energies, above 1 MeV.