Experimental study of laser-driven proton acceleration with ultrathin targets

The generation of proton beams from thin-foil targets on SILEX-Ⅰ is studied. It shows that prepulse has a profound effect on the maximum proton energy. The thinner the target is, the more sensitive it is to the prepulse. Under the laser intensity of 1018 to 3×1019 W/cm2, the maximum proton energy is 0.54 MeV with 190 nm CH target and 3.15 MeV with 3 μm Cu target (back surface plated with 4 μm CH) respectively. Besides, the effect of laser polarization on proton acceleration is also studied. The maximum proton energy accelerated by a circularly polarized laser pulse is a little lower than that by a P-polarized laser pulse with the same laser power density. The mechanism is consistent with target normal sheath acceleration.