Suppression of transverse proton beam divergence by controlled electron cloud in laser-plasma interactions

Abstract

In this paper, suppression of a transverse proton divergence is focused by using a controlled electron cloud. When an intense short pulse laser illuminates a foil plasma target, first electrons are accelerated and they form a strong electrostatic field at the target surface, then ions are accelerated by the strong field. When a target has a hole at the opposite side of the laser illumination, an electron cloud is limited in transverse direction by a neutral plasma at the protuberant part. The proton beam is accelerated and also controlled by transverse shaped electron cloud, and consequently the transverse divergence of the proton beam is suppressed. In 2.5-dimensional particle-in-cell simulations, the transverse shape of the electron cloud is controlled well and the transverse proton beam divergence is suppressed successfully; the transverse emittance is improved by about 28% compared with that in a conventional slab target.