  We propose a novel mechanism for ion acceleration based on the guided motion
of electrons from a thin target. The electron motion is locked to the moving
nodes of a standing wave formed by a chirped laser pulse reflected from a
mirror behind the target. This provides a stable longitudinal field of charge
separation, thus giving rise to chirped standing wave acceleration (CSWA) of
the residual ions of the layer. We demonstrate, both analytically and
numerically, that quasi-monoenergetic ion beams with energies of the order 100
MeV are feasible for realistic pulse energies of 10 J. Moreover, a scaling law
for higher laser intensities and layer densities is presented, indicating
stable GeV-level energy gains of dense ion bunches, for soon-to-be available
laser intensities.
