Theoretical Study of the Efficient Ion Acceleration Driven by Petawatt-Class Lasers via Stable Radiation Pressure Acceleration

Meng Liu,Jia-Xiang Gao,Yu-Tong Li,Wei-Min Wang

doi:10.3390/app12062924

Abstract

Laser-driven radiation pressure acceleration (RPA) is one of the most promising candidates to achieve quasi-monoenergetic ion beams. In particular, many petawatt systems are under construction or in the planning phase. Here, a stable radiation pressure acceleration (SRPA) scheme is investigated, in which a circularly-polarized (CP) laser pulse illuminates a CH2 thin foil followed by a large-scale near-critical-density (NCD) plasma. In the laser-foil interaction, a longitudinal charge-separated electric field is excited to accelerate ions together with the heating of electrons. The heating can be alleviated by the continuous replenishment of cold electrons of the NCD plasma as the laser pulse and the pre-accelerated ions enter into the NCD plasma. With the relativistically transparent propagation of the pulse in the NCD plasma, the accelerating field with large amplitude is persistent, and its propagating speed becomes relatively low, which further accelerates the pre-accelerated ions. Our particle-in-cell (PIC) simulation shows that the SRPA scheme works efficiently with the laser intensity ranging from 6.85×1021 W cm−2 to 4.38×1023 W cm−2, e.g., a well-collimated quasi-monoenergetic proton beam with peak energy ∼1.2 GeV can be generated by a 2.74 × 1022 W cm−2 pulse, and the energy conversion efficiency from the laser pulse to the proton beam is about 16%. The QED effects have slight influence on this SRPA scheme.

Highlights

Laser-driven ion accelerators are characterized by their large accelerating field gradient and have attracted significant attention over the past two decades [1–4]
We propose a stable radiation pressure acceleration (SRPA) scheme by using a combination target of a CH2 thin foil and a large-scale near-critical-density (NCD) plasma
It is worth pointing out that our stable radiation pressure acceleration (SRPA) scheme could provide a reference for the ion acceleration experiments with PW-class laser systems recently available and 10-PW-class laser systems available in the near future [54,55]

Summary

Introduction

Laser-driven ion accelerators are characterized by their large accelerating field gradient and have attracted significant attention over the past two decades [1–4]. With the development of a multi-petawattclass laser system, intensities of 1022 ∼1023 W cm−2 can be reached, for which the generation of monoenergetic GeV ion beams is one of the primary applications based on light-sail mode of RPA [28] This model is usually plagued by strong electron heating due to the onset of transverse instabilities [29–31] and finite spot size [32]. Significant efforts [33–36] have been devoted to overcoming the limitations of this mechanism to improve the ion beam qualities, such as transverse divergence, the maximum energy, and the energy spread Most of these scenarios are still demanded to be verified in the future experiments with the developing laser technology.

Theory and Analysis

Particle-In-Cell Simulation Results

Findings

Conclusions