130,639 research outputs found
Proton emission from resonant laser absorption and self-focusing effects from hydrogenated structures
No full textEffects of resonant absorption and self-focusing are investigated by using fast and intense laser pulses. The ion emission and acceleration in the non-equilibrium laser-generated plasma are investigated at low and high intensities, from 1010 up to about 1016 W/cm2.
The properties of plasma are strongly dependent on the time and space, laser intensity and wavelength.
A special interest concerns the energetic and intense proton generation for the multiplicity use that proton beams have in different scientific fields (Nuclear Physics, Astrophysics, Bio-Medicine, Microelecronics, etc.).
Investigations have been performed at INFN-LNS of Catania and at PALS Laboratory of Prague, by using thick and thin targets and different technique of ion analysis.
The mechanisms of resonant absorption of the laser light, produced in special targets containing nanostructures with dimensions comparable with the laser wavelength, enhances the proton energy. The mechanisms of self-focusing, obtained by changing the laser focal distance from the target surface, increase the local intensity and consequently the high directional ion acceleration.
Real-time ion detections were performed through Thomson parabola spectrometer (TPS), ion collectors (IC), SiC detectors and ion energy analyzer (IEA) employed in time-of-flight configuration (TOF).
The energy and the amount of ions increase significantly when the two non-linear phenomena occurs, as will be described
Real-Time Diagnostics of Fast Light Ion Beams Accelerated by a sub-Nanosecond Laser
No full textMulti-MeV proton and light ion beams had been produced using the 300 ps, kJ-class iodine laser, operating at Prague Asterix Laser System (PALS) Centre in Prague. The target material had been chosen in such a way so as to increase the proton beam current density (approaching 0.1 A/cm2 at the distance of 1 m from the source). The real-time ion detection was performed by means of a standard flat and ring ion collectors (IC) in the time-of-flight (TOF) configuration. The ICs had been shielded with aluminum foils of various thickness, in order to cut the long photo-peak contribution that is usually overlapping with the ultrafast particle signal, and to analyze mainly the laser-accelerated proton beam. The processing of the obtained experimental IC data is described in some detail, including the deconvolution of TOF signals, evaluation of the UV/soft-X-ray photo-peak absorption, and ion transmission calculations for different metallic filters
Laser fusion system and method
No full textReazione di fusione nucleare indotta da laser su target di silici
Particle size determination of silver nanoparticles generated by plasma laser ablation by means deconvolution method
No full textSilver nanoparticles were synthesized in vacuum (10−7) by using a Nd:YAG high-power pulsed laser
without any catalytic gas and/or thermal annealing processes. The ablated material was collected on
several SiO2/Si substrates (with 50 nm thickness) deposited before the laser ablation with a plasmaenhanced
chemical vapor deposition system. The substrates were analyzed with the aid of a variable angle
spectra ellipsometer at different angles. The analysis revealed the presence of a surface plasmon resonance
at about 3 eV, which is in good agreement with results in the literature.Adeconvolution method utilizing the
Lorentz model was applied to fit the experimental optical absorption peaks in order to recognize different
groups of nanoclusters with different sizes varying from 2 to 10 nm in radius. Electronic elaborations
of scanning electron microscopy of the embedded particles in the SiO2 matrix were also carried out to
measure their densities as a function of the deposition time and dimension distributions. The experimental
measurements were performed at the INFN-LNS laboratory of Catania and at the MT laboratory of the
FBK-IRST foundation of Trento
Laser-generated plasma investigation by electrostatic quadrupole analyzer
No full textA study of different metallic targets ablation, in vacuum, by using a 3ns Nd:YAG laser radiation, 532nm wavelength, is reported. Laser pulse with a high intensity generates a plasma at the target surface, with high non-isotropic emission of neutral and ion species, mainly emitted along the normal to the target surface. Mass quadrupole spectrometry, associated to the electrostatic ion deflection, allows an estimation of the emitted charge states energy distributions, within the plasma plume, for a fixed incident laser energy. Neutrals show Boltzmann-like distributions while ions show Coulomb-Boltzmann- shifted distributions. Time-of-flight measurements were also performed by using an ion collector consisting of a collimated Faraday cup placed along the normal to the target surface. The plasma is investigated in terms of velocity, kinetic energy, ion charge state and temperature of the ejected particles. A special regard is given to the parameters that influence the plasma properties, such as the evaporation latent heat, the electrical conductivity and the electron density of the ablated elements, to the plasma temperature and density and to the evaluation of the electric field producing the ion acceleration inside the plasma
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