Spatial characteristics of K alpha x-ray emission from relativistic femtosecond laser plasmas
Reich, C × Uschmann, I Ewald, F Dusterer, S Lubcke, A Schwoerer, H Sauerbrey, R Forster, E Gibbon, Paul #
Published by the American Physical Society through the American Institute of Physics
Physical Review E, Statistical, Nonlinear and Soft Matter Physics vol:68 issue:5
The spatial structure of the Kalpha emission from Ti targets irradiated with a high intensity femtosecond laser has been studied using a two-dimensional monochromatic imaging technique. For laser intensities I<5x10(17) W/cm(2), the observed spatial structure of the Kalpha emission can be explained by the scattering of the hot electrons inside the solid with the help of a hybrid particle-in-cell/Monte Carlo model. By contrast, at the maximum laser intensity I=7x10(18) W/cm(2) the half-width of the Kalpha emission was 70 mum compared to a laser-focus half-width of 3 mum. Moreover, the main Kalpha peak was surrounded by a halo of weak Kalpha emission with a diameter of 400 mum and the Kalpha intensity at the source center did not increase with increasing laser intensity. These three features point to the existence of strong self-induced fields, which redirect the hot electrons over the target surface.