TNSA ion acceleration at 10¹⁶ W/cm² sub-nanosecond laser intensity

Micrometric thin targets have been irradiated in vacuum in TNSA (Target Normal Sheath Acceleration) configuration at PALS Laboratory in Prague by using 10¹⁶ W/cm² laser intensity, 1315 nm wavelength, 300 ps pulse duration and different laser beam energies and focal positions. The plasmas produced were characterized by using ion collectors, semiconductor SiC detectors, X-ray streak camera and Thomson parabola spectrometer. Time of flight techniques, time resolved imaging and ion deflection spectrometry were used to characterize the laser-generated non-equilibrium plasma and the electric field driving ion acceleration developed at the rear side of the target. The maximum ion acceleration can be obtained for optimal film thickness depending on the laser energy and on the kind of irradiated targets. Special targets containing nanostructures, showing high absorption and low reflective coefficients, induce resonant absorption effects enhancing the electric acceleration field. The maximum kinetic energy measured for proton ions was above 5.0 MeV and the ion distributions can be fitted with Coulomb-Boltzmann shifted functions.