High-quality return relativistic electron beam by intense laser pulse in a low-density foil plasma

Electron acceleration by intense laser beam interaction with an under-dense plasma layer was examined by particle simulations. A novel phenomenon of short high-quality, well-collimated return relativistic electron beam was observed in the direction opposite to laser propagation. The formation of an electron beam, its characteristics and the time-history of test electrons were illustrated and analyzed. A novel two-phase electron acceleration mechanism - the initial stage induced by forward stimulated Raman scattering and the second one by the buildup of a large sheath electrostatic field, which operates like a two-stage accelerator - was proposed. (author)