Bunched Proton Acceleration from a Laser-Irradiated Cone Target

Abstract

Laser-driven ion acceleration is an attractive technique to generate compact high-energy ion sources. Currently, among various physical and technical issues to be solved, boosting the ion energy and reducing the energy spread represent the key challenges with this technique. Here we present a scheme to tackle these challenges by using a hundred-terawatt-class laser pulse irradiating a cone target. Three-dimensional particle-in-cell simulations show that a large number of electrons are dragged out of the cone walls and accelerated to hundreds of MeV by the laser fields inside the cone. When these energetic dense electron beams pass through the cone target tip into vacuum, a very high bunching acceleration field, up to tens of TV/m, quickly forms. Protons are accelerated and simultaneously bunched by this field, resulting in quasimonoenergetic proton beams with 100 MeV energy and low energy spread of about 2%. Results exploring the scaling of the proton beam energy with laser and target parameters are presented, indicating that the scheme is robust. This opens an efficient route for compact high-energy proton sources for fundamental research and biomedical applications.