Simulation of the Quasi-Monoenergetic Protons Generation by Parallel Laser Pulses Interaction with Foils

A new scheme of radiation pressure acceleration for generating high-quality protons by using two overlapping-parallel laser pulses is proposed. Particle-in-cell simulation shows that the overlapping of two pulses with identical Gaussian profiles in space and trapezoidal profiles in the time domain can result in a composite light pulse with a spatial profile suitable for stable acceleration of protons to high energies. At ～2.46×10²¹ W/cm² intensity of the combination light pulse, a quasi-monoenergetic proton beam with peak energy ～200 MeV/nucleon, energy spread <15%, and divergency angle <4° is obtained, which is appropriate for tumor therapy. The proton beam quality can be controlled by adjusting the incidence points of two laser pulses.