Distinguished role of the laser pulse temporal structure on deuteron acceleration

Compared to their conventional counterpart, laser plasma-based ion accelerators offer considerably higher acceleration gradients, opening the way to more compact laser-driven accelerator facilities. In this context, deuteron acceleration has been used for laser-based neutron sources, as deuterons at relatively low kinetic energy can efficiently generate neutrons. While double-pulse and chirp effects have been explored for proton acceleration under radiation pressure and target-normal sheath acceleration schemes, their role in ion acceleration remains unconfirmed, limiting the optimization strategies for neutron sources. Here we clarify the influence of laser pulse temporal shape on ion acceleration from ultrathin targets. We systematically change the temporal structure of the pulse by controlling the group delay dispersion and third-order dispersion (TOD), while pulse energy and focal spot size remain unchanged. The experiments are supported by 2D PIC simulations and analytical modeling. We find that the effect of optimum temporal shape is considerably larger than previously reported: the TOD-induced post-pulses increase the efficiency by 50% and double the deuteron cutoff energy. Our systematic study shows that the performance of laser ion accelerators can be strongly enhanced by matching the dispersion values to the target characteristics. The higher acceleration gradients of laser ion accelerators opens the way to more compact laser-driven accelerator facilities than the existing conventional ones. The authors find that the acceleration performance is doubled with the use of temporally shaped laser pulses showing that the shaping parameters, easy to introduce in modern lasers, depend on the target characteristics.