Production of high energy protons with hole-boring radiation pressure acceleration

The possibility of producing energetic protons with energies in the range of 100-200 MeV via hole-boring (HB) radiation pressure acceleration (RPA) at intensities around 10(21) W cm(-2) is reexamined. It is found that hole-boring RPA can occur well below the relativistically corrected critical density in numerical simulations, with average proton energies in good agreement with established formulas. This suggests that protons in this energy range can be produced via HB RPA at around 10(21) W cm(-2). It is also shown that the prospects of doing this could be improved by using lasers of the same intensity but longer wavelength. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562551]