Copious positron production by femto-second laser via absorption enhancement in a microstructured surface target

Laser-driven positron production is expected to provide a non-radioactive, controllable, radiation tunable positron source in laboratories. We propose a novel approach of positron production by using a femto-second laser irradiating a microstructured surface target combined with a high-Z converter. By numerical simulations, it is shown that both the temperature and the maximum kinetic energy of electrons can be greatly enhanced by using a microstructured surface target instead of a planar target. When these energetic electrons shoot into a high Z converter, copious positrons are produced via Bethe-Heitler mechanism. With a laser (wavelength lambda = 1 mu m) with duration similar to 36 fs, intensity similar to 5.5 x 10(20) W/cm(2) and energy similar to 6 Joule, similar to 10(9) positrons can be obtained.