  Monoenergetic ion bunch generation and acceleration from double layer thin
foil target irradiated by intense linearly polarized (LP) laser pulse is
investigated using two-dimensional (2D) particle-in-cell (PIC) simulations. The
low-Z ions in the front layer of the target are accelerated by the laser-driven
hot electrons and penetrate through the high-Z ion layer to generate a
quasi-monoenergetic ion bunch, and this bunch will continue to be accelerated
by the quasi-stable electrostatic sheath field which is formed by the immobile
high-Z ions and the hot electrons. This mechanism offers possibility to
generate monoenergetic ion bunch without ultrahigh-contrast and ultrahigh
gradient laser pulses in beam generation experiments, which is confirmed by our
simulations.
