Ultra-intense laser pulse absorption and fast particles generation at interaction with inhomogeneous foil target

The absorption of a short laser pulse with duration 40 fs and the intensity more than 1018 W/cm2 at the interaction with foil targets is analyzed in the theory and particle-in-cell (PIC) simulations. Initially, foil target density distribution has a smooth gradient with a variable scale-length of plasma density inhomogenity L. Laser absorbed energy transforms into the energy of fast electrons, which oscillate in the foil and partly go out from the target transforming their energy into accelerated ions. The analyses of the different mechanisms of ion acceleration in foil plasma, the influence of L and other plasma parameters on ion acceleration have been done. The angular distributions of fast electron and ion beams are calculated. The optimum laser plasma conditions for the maximum ion acceleration are found