Monoenergetic proton beams accelerated by circularly polarized laser with thin solid foils

The acceleration of ions in the interaction of circular polarized laser pulses with overdense plasmas is investigated. For circular polarization laser pulses, the quasi-equilibrium for electrons is established due to the light pressure and the electrostatic field built up at the interacting front of the laser pulse. The ions located within the skin-depth of the laser pulse can be synchronously accelerated and bunched in the charge couple processes by the electrostatic field, and thereby monoenergetic and high intensity proton beam can be generated. The dynamics equations for accelerated ions are deduced and proved by particle-in-cell simulations.