An intense collimated beam of high-energy protons is emitted normal to the rear surface of thin solid targets irradiated at 1 PW power and peak intensity $3\times {10}^{20}\mathrm{W}{\mathrm{cm}}^{-2\mathrm{}}$. Up to 48 J ( $12\%$) of the laser energy is transferred to $2\times {10}^{13}$ protons of energy $>10\mathrm{}\mathrm{MeV}$. The energy spectrum exhibits a sharp high-energy cutoff as high as 58 MeV on the axis of the beam which decreases in energy with increasing off axis angle. Proton induced nuclear processes have been observed and used to characterize the beam.

• Received 19 January 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.2945