Laser interaction with nano-structured target and their applications in high energy density physics

Abstract

In order to improve the total laser-proton energy conversion efficiency, a nanobrush target is proposed. Compared with foil target, the sheath field on the rear surface of nanobrush target is increased near 100% and the energy efficiency from laser to proton is prompted more than 70%. Meanwhile, the proton beam is well collimated with divergence angle less than 30degree. As sub-wavelength nanolayered target and conical targets both enhance laser absorption compared with foil targets, we propose a conical nanolayered target in trying to improve coupling efficiency. Compared with nanolayered target, the energy coupling efficiency is enhanced from 34% to more than 68%. Detailed simulations indicate that this enhancement is attributed to both oblique incidence and focusing of the conical target. Moreover, the conical nanolayered target collimates the hot electrons better. The conical nanobrush target is used to improve the total proton energy-conversion efficiency in proton beam acceleration. Results indicate a significant enhancement of the number and energies of hot electrons through the target rear side of the conical nanobrush target. Compared with the plain target, the field increases several times. We observe enhancements of the average proton energy and total laserproton energy conversion efficiency of 105%. This enhancement is attributed to both nanobrush and conical configurations. The proton beam is well collimated with a divergence angle less than 28degree.