Laser-generated plasma investigation by electrostatic quadrupole analyzer

Abstract

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.