Yield and spatial distributions of femtosecond laser-produced protons

For studing the yield and spatial distributions of protons produced in the interaction of femtosecond laser with plasmas, protons behavior at the normal direction of the rear surface of the target irradiated by ultra-intensity pulse laser irradiated solid targets was explored on SILEX-I laser facility. The yield and spatial distributions of the protons with different target thicknesses were recorded by radiochromic film (RCF) HD810. The results show that the optics density (OD) is closely correlated with the protons flux, OD values increase with the increasing of proton beam flux;For fixed thickness of C8H8 layer, the proton beam flux and yield of protons and OD of RCF decrease with the increasing Cu layer thickness;for the same thickness of targets, the OD and yield of protons decrease with the decreases of laser intensity;And the corresponding spatial profile of proton beam shows ring-, filament-, and disc-like distribution. The size of the distribution is independent of laser focus.