A simple way to introduce an adjustable femtosecond pre-pulse to enhance laser-driven proton acceleration

We demonstrate a simple way to introduce a femtosecond pre-pulse with adjustable intensity and delay without using an additional compressor to enhance laser-driven proton acceleration. Targets with different thicknesses were shoot at normal incidence by varying the pre-pulses. Experimental results show that significant enhancement of the proton energy can be achieved when the intensity of pre-pulse is optimized. Density profile of preplasma was obtained by hydrodynamic simulations. PIC simulations reveal that the preplasma generated by a femtosecond pre-pulse can increase the intensity of main pulse. (paper)