Heavy ion acceleration by ultra-intense laser pulses interaction with a tapered nanowire target

In this study, we propose a novel composite carbon nanowire target with a tapered structure to enhance the acceleration of ion by the space-charge field. The numerical study based on two-dimensional particle-in-cell simulations has been carried out, and the physical mechanisms behind the acceleration of C6+ to energies much higher than those of a laser interacting with a normal nanowire target are reported. When the ultra-intense laser interacts with the tapered nanowire target, not only are the electrons accelerated more effectively, resulting in an enhanced sheath field on the back of the target, but also a strong forward quasi-static electric field is generated inside the target. Thus, there is a phenomenon that the C6+ ions are accelerated to higher energies in two stages by the quasi-static electrostatic fields inside and behind the target. In addition, in order to investigate the most efficient case of C6+ ion acceleration, the particle-in-cell simulations were also carried out using different laser intensities and target parameters.