Radiation pressure acceleration of thin foils with circularly polarized laser pulses

A new regime is described for radiation pressure acceleration of a thin foil by an intense laser beam of above 10 20 W cm −2 . Highly monoenergetic proton beams extending to giga-electron-volt energies can be produced with very high efficiency using circularly polarized light. The proton beams have a very small divergence angle (<4°). This new method allows the construction of ultra-compact proton and ion accelerators with ultra-short particle bursts.