Transport characteristic of hot electron bunches in solid targets by transition radiation

For exploring the transport characteristic of hot electron bunches, the integrated image pattern of optical transition radiation were measured at the normal direction of the rear side of targets employing the optical CCD camera. The experiment was carried out on the 100 TW laser. The transition radiation facula on the rear side of a 20 μm thick target Ta was a smooth round structure with the center brighter than the periphery, indicating incoherent transition radiation and coherent transition radiation, which is close to the results of the theoretical simulations. For a 100 μm thick target Ta, the facula was a star-structure and became smaller, which resembles a star-structure of the energetic proton emission. For a 10 μm Ta + 10 μm Cu+5 μm Ta composite target, the facula was a ring s