  A regime of multi-cascade proton acceleration in the interaction of
$10^{21}-10^{22}$ W/cm$^2$ laser pulse with a structured target is proposed.
The regime is based on the electron charge displacement under the action of
laser ponderomotive force and on the effect of relativistically induced slab
transparency which allows to realize idea of multi-cascade acceleration. It is
shown that a target comprising several properly spaced apart thin foils can
optimize the acceleration process and give at the output quasi-monoenergetic
beams of protons with energies up to hundreds of MeV with energy spread of just
few percent.
