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Proton emission from laser - generated plasmas at different intensities

Torrisi L., Cutroneo M., Cavallaro S., Giuffrida L., Margarone D.

Nukleonika

2012

Vol. 57, No. 2

237-240

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.

Post-acceleration of ions from the laser-generated plasma

Giuffrida L., Torrisi L.

Nukleonika

2011

Vol. 56, No. 2

161-163

An application of the laser-generated plasma for multi-energetic ion implantation is reported. In an experiment performed at Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud (INFN-LNS) of Catania, Italy the Nd:YAG laser was used, operating at the 1064 nm wavelength with the intensity of 1010 W/cm2. A laser pulse of 9 ns duration and 300 mJ energy was employed to ablate a solid target placed in a high vacuum. The free ion expansion occurred in a constant potential chamber placed at 30 kV positive voltage with respect to the ground, which allowed to extract ions with energy proportional to the charge state. In an another experiment, performed at the PALS Prague laser facility (1315 nm, 400 ps pulse width and the laser pulse energy delivered on target equal to about 35 J) Ti ions were obtained through the ablation of solid targets in vacuum by means of 1015 W/cm2 laser pulses. In both cases ion energy analyzers were used to measure the energy-to-charge ratio of the ions. The ion energy distribution was determined from the time-of-flight measurements. The depth profiles measured through Rutherford backscattering spectrometry (RBS) analysis are in good agreement with the ion energy analyzer spectroscopy measurements.