INFLUENCE OF AXIAL MAGNETIC FIELD TRAP ON LASER-GENERATED PLASMA

Abstract- In vacuum plasma generated by laser ablation of metallic targets (Cu and Ta) was investigated with and without the influence of 0.1 T axial magnetic field. The laser beam intensity, of the order of 1010 W/cm2, was obtained by a Nd:Yag operating at 1064 nm wavelength, 9 ns pulse width and 500 mJ pulse energy. Time-of-flight measurements of ion emission were performed along the direction normal to the target surface by using an ion collector. Results demonstrated that the magnetic field creates an electron trap in front of the target. The electron charge density inside the trap modifies the electric potentials in the plasma inducing an higher ion acceleration. The presence of the electron cloud not only focuses the ion beam but also increases its energy, mean charge state and current. Introduction- Laser-generated plasma in vacuum are characterized by high temperature and density, high charge state and high ion energies along the expanding direction, i.e. orthogonally to the ablated target surface. Measurements with an ion energy analyser demonstrate that the distributions follow a “Coulomb-Boltzmann-shifted ” function, as reported in previous experiments [1]. Increasing the charge state the ion kinetic energ