Postacceleration of laser-generated high-energy protons through conventional accelerator linacs

The postacceleration of laser-generated protons through conventional drift-tube linear accelerators (linacs) (DTLs) has been simulated with the particle-code PARMELA. The proton source is generated on the rear surface of a target irradiated by an high-intensity (10¹⁹ W · cm^-2) short-pulse (350 fs) laser and focused by a microlens that allows selecting collimated protons at 7 ± 0.1 MeV with root-mean-square unnormalized transverse emittance of 0.180 mm · mrad. The simulations show that protons can be accelerated by one DTL tank to more than 14 MeV with unnormalized transverse-emittance growth of 8 and 22.6 in different transverse directions when considering a total proton charge of 0.112 mA. This first numerical study shows that coupling between laser-plasma accelerators with traditional accelerators is possible, allowing a luminosity gain for the final beam.