Backward Plasma Acceleration of Aluminum, Copper, Silver, and Tantalum Ions From 10^10 up to 10^15 W/cm^2 Pulse Laser Intensity

Measurements of ion acceleration in laser-generated plasma obtained at intensities from 10^10 up to 10^15 W/cm^2 using IR laserablation of aluminum, copper, silver, and tantalum in high vacuum are presented. At low intensity, data were acquired from the MIFT Department of Messina University (Italy) using a Q-switched Nd:YAG laser operating at 1064 nm, and at high intensity fromthe PALS Laboratory (Czech Republic) using the Asterix Iodine laser operating at 1315 nm. In both cases, ions were detected usinga Faraday cup as an ion collector to measure their energy via time-of-flight, and an ion energy analyzer with electrostatic deflection to evaluate the ion charge state. The ablation yield, in terms of the mass removed per laser pulse, was acquired. Measurements demonstrated that the ion acceleration depends strongly on the laser intensity. Moreover, at low intensity, the maximum ion energy is not very dependent on the focal position with respect to the target surface. In contrast, at high intensity, it is strongly dependent on this parameter. The Coulomb-Boltzmann-shifted theory is applicable in both cases. Applications of produced ions to the deposition of thin films and to substrate ion implantation have been reported and discussed.