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Abstract: Protons production and acceleration via laser-generated plasma from thin Fe2O3 and carbon nano-tubes doped polyethylene films are investigated at relatively low laser pulse intensity, of the order of 1010 W/cm2. Time-of-flight technique is employed in order to measure the proton energy and the relative yield with respect to the carbon one. Two ion collectors are used in opposite directions to detect the proton energy and yield both in backward and forward directions, normally to the irradiated target surface, as a function of the thin target doping concentration. The comparison between the results obtained with thin films doped with two nano-particle species is presented and discussed, with a special regard to the high proton emission. [Copyright &y& Elsevier]

A Nd:YAG laser operating in second harmonic (532 nm), 3 ns pulse duration, 150 mJ pulse energy, and 10 Hz repetition rate, is employed to irradiate Al2O3 target placed in high vacuum. The produced plasma is investigated by an ion collector used in time-of-flight configuration and by a mass quadrupole spectrometer, in order to determine the equivalent plasma temperature and the atomic and molecular composition. Pulsed laser deposition technique has been used to produce thin films on different substrates placed close to the target. Different surface analyses, such as energy dispersive X-ray fluorescence (EDXRF), X-ray photoelectron spectroscopy (XPS) and surface profilometry are employed to characterize the produced films. Measurements of ablation yield, plasma equivalent temperature, acceleration voltage and characterization of grown thin films are presented and discussed. [ABSTRACT FROM AUTHOR]

A pulsed Nd:Yag laser, at intensities of the order of 1010 W/cm2, is employed to irradiate different thick metallic targets (Ti, Fe, Ag, and Ni) placed in vacuum. The obtained non-equilibrium plasmas are investigated with various analytical techniques. An electrostatic ion energy analyzer and different ion collectors are employed to monitor in situ the ions ejected from the plasma and to determine the core plasma temperature, the ion energy distributions and the ion angular emission. An optical spectrometer is employed to analyze the plasma corona emitted light vs. wavelength and to identify the emitted characteristic lines. The optical spectroscopy permitted to evaluate the electron temperatures and densities. Results show strong temperature and density gradients occurring in the laser-generated plasma plume. [ABSTRACT FROM AUTHOR]

A comparison between laser ablation of nickel in vacuum by using 532-and 1064-nm Nd:YAG (Yttrium Aluminium Garnet) laser wavelengths, with an intensity of 5 × 109 W/cm2, is reported. Nanosecond pulsed ablation produces high nonisotropic emission of neutrals and ionic species. For 532-nm laser irradiation, mass quadrupole spectrometry, coupled to electrostatic ion deflection and time-of-flight measurements, allows estimation of the energy distributions of the emitted species from plasma. For 1064-nm laser ablation, a cylindrical electrostatic ion analyzer permits one to measure the yield and the charge state of the emitted ions and reconstruct the ion energy and charge state distributions. Neutrals show typical Boltzmann-like distributions, while ions show Coulomb-Boltzmann-shifted distributions depending on their charge state. Surface profiles of the ablated craters permitted study of the ablation threshold and yields of nickel in vacuum versus the laser fluence. The plasma temperature was evaluated using experimental data. Special regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated at nonequilibrium plasma conditions and the angular distribution of the emitted species. [ABSTRACT FROM AUTHOR]

A study of different metallic targets ablation, in vacuum, by using a 3 ns Nd:YAG laser radiation, 532 nm 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. [ABSTRACT FROM AUTHOR]

Laser-generated plasma in vacuum are obtained ablating hydrogenated polymers at the Physics Department of Messina University and Prague Asterix Laser System laboratory of Prague. In the first case, a 3-ns, 532-nm Nd:Yag laser at 5×109 W/cm2 intensity was employed. In the second case, a 300-ps, 438-nm iodine laser at 5×1014 W/cm2 intensity was employed. Different ion collectors are used in time-of-flight configuration to monitor 'on line' the ejected ions from the plasma at different angles with respect to the normal direction to the target surface. Measurements demonstrated that the mean ion velocity, directed orthogonally to the target, increases for ablation of polymers doped with metallic elements (Br, Cu, Au and W) with respect to that obtained with no-doped polymers. The possible mechanism explaining the results can be found in the different electron density of the plasma, due to the higher number of electrons coming from the metallic doping elements. This charge enhancement increases the equivalent ion voltage acceleration, i.e. the electric field generated in the non-equilibrium plasma placed in front of the ablated target surface. [ABSTRACT FROM AUTHOR]

Abstract: A study of laser-generated plasma by visible laser ablation of aluminium, in high vacuum (3×10−7 mbar), by using 3ns Nd:YAG laser radiation, is reported. Nanosecond pulsed ablation, at intensity of the order of 1010 W/cm2, gives an emission of neutral and charged particles. A special mass quadrupole spectrometer, operating in the 1–300amu mass range, was used to analyse the energetic atomic emission produced by the laser ablation. Neutrals show typical Boltzmann distributions, directly correlated to the plasma temperature, while ions show Coulomb–Boltzmann-shifted distributions depending on their charge state. Surface profiles of the craters and microscopy investigations permitted to study the ablation threshold and the ablation yields. The multi-component structure of the plasma plume emission is investigated in terms of charge state, neutrals and ions temperature. A special regard is given to the study of the ion acceleration process occurring inside the plasma due to a high electrical field generated in the non-equilibrium plasma. The angular distributions of the neutral and ion particles are also presented and discussed. [Copyright &y& Elsevier]

A Nd:YAG laser with 10 9 W/cm 2 pulse intensity, operating at 532 nm wavelength, is used to ablate Ta and Cu targets placed in vacuum. The ablation process generates a plasma in front of the target surface, which expands along the normal to target surface. The ion and electron emissions from the plasma were measured by Faraday cups placed at different angles with respect to the normal to target surface. In the range of laser intensities from 10 7 to 10 9 W/cm 2 , the fast electron yield is lower than the ion yield and it increases at higher laser intensities. The ablation threshold, the emission yield, the ion and electron average energies and the plasma ion and electron temperatures were measured for ion and fast electron streams. [ABSTRACT FROM AUTHOR]

Abstract: Titanium-plasma was obtained by nanosecond pulsed laser ablation technique. A Nd:Yag laser was employed to irradiate titanium in vacuum. The ion emission from plasma was on-line monitored by an electrostatic ion energy analyzer which permitted to measure the ion kinetic energy and charge state. The visible photon emission was monitored by an optical spectrometer. The ion energy, charge state and angular distributions, the temperature and density of the non-equilibrium plasma were investigated. The temperature gradient of the plasma plume was evaluated and discussed. [Copyright &y& Elsevier]