Quasi-monoenergetic proton beam from a proton-layer embedded metal foil irradiated by an intense laser pulse

Abstract

A target structure, ion-layer embedded foil (ILEF) is proposed for producing a quasi-monoenergetic proton beam by utilizing a bulk electrostatic field, which is generated by irradiating the target with an ultra-intense laser pulse, inside the plasma. Compared with the case of a single metal foil in which the proton layer is initially present on the surface, in the ILEF target, the proton layer is initially located inside a metal foil. A two-dimensional particle-in-cell (PIC) simulation shows that the target generates a proton beam with a narrow energy spread. With a laser intensity of 2 × 1019 W/cm2, a 22-MeV proton beam with an energy spread of 8% at the full-width-half-maximum (FWHM) is obtained when the proton layer is located at 0.4 μm inside the rear surface of a 2.4 μm-thick copper foil. When the proton layer moves toward the front side, a proton beam with a flat-top energy distribution ranging from 15 MeV to 35 MeV is obtained. Further, with a higher laser intensity of 1021 W/cm2, a proton beam with the maximum energy of 345 MeV and FWHM energy spread of 7.2% is obtained. The analysis of the PIC simulation with an aid of a fluid analysis shows that the spectrum is affected by the initial position of the proton layer, its initial spread during the formation of the sheath field, and the space charge effect.

Summary of laser plasma physics sessions at the first AAPPS-DPP conference

“…Lee [L-I15] from Korea Atomic Energy Research Institute reported a new type of layered target for the generation of an energetic proton beam with narrow energy spread. In this target, the ion layer was embedded inside the foil target and ion acceleration if realized by utilizing a bulk electrostatic field in the plasma (Kim et al 2016). Under optimized target parameters, protons can be accelerated to around 300 MeV with quasi-monoenergetic spectrum under the peak laser intensity of 10 21 W/cm 2 based upon their numerical simulation.…”