  The production of ion beams from the interaction of a circularly polarized
laser pulse with a nanometric double-layer target is discussed in the regime
where all electrons are expelled from the target by laser radiation pressure.
Quasi-monochromatic, well-collimated ion beams are observed in two-dimensional
particle-in-cell simulations. The ion beam properties are derived from a simple
analytical model, and the possibility to control those properties by using a
laser-pulse with sharp-rising edge is discussed. Potential application to
hadron-therapy is finally considered.
