Stable GeV Ion-Beam Acceleration from Thin Foils by Circularly Polarized Laser Pulses

Abstract

A stable relativistic ion acceleration regime for thin foils irradiated by circularly polarized laser pulses is suggested. In this regime, the “light-sail” stage of radiation pressure acceleration for ions is smoothly connected with the initial relativistic “hole-boring” stage, and a defined relationship between laser intensity $I_0$, foil density $n_0$, and thickness $l_0$ should be satisfied. For foils with a wide range of $n_0$, the required $I_0$ and $l_0$ for the regime are theoretically estimated and verified with the particle-in-cell code ILLUMINATION. It is shown for the first time by 2D simulations that high-density monoenergetic ion beams with energy above $\mathrm{GeV}/\mathrm{u}$ and divergence of 10° are produced by circularly polarized lasers at intensities of ${10}^{22}\mathrm{W}/{\mathrm{cm}}^2$, which are within reach of current laser systems.