Low-divergence relativistic proton jet from a thin solid target driven by an ultra-intense circularly polarized Laguerre–Gaussian laser pulse

We propose a new ion acceleration scheme of irradiating a thin solid target with an ultraintense circularly polarized Laguerre–Gaussian (LG) laser pulse. Three-dimensional particle-in-cell simulations are performed to demonstrate that this scheme can generate a low-divergence high-density relativistic proton jet. By this scheme, the number of protons emitted with a small angle (<1°) from the laser axis can be more than tens of times as high as that of the protons accelerated by a circularly polarized Gaussian pulse. The inward ponderomotive force of the LG pulse drives such a proton beam along the laser axis.