New injection and acceleration scheme of positrons in the laser-plasma bubble regime

Z Y Xu,P P Rajeev,C F Xiao,C Z Xie,D Neely,H G Lu,J X Liu,T Q Xu,H Y Lu,J Q Yu,X Q Yan,S Li,Y R Shou,R X Li,R H Hu,Z Gong,N Hafz,S Y Chen,Z Najmudin

doi:10.1103/physrevaccelbeams.23.091301

Abstract

A novel approach for positron injection and acceleration in laser driven plasma wakefield is proposed. A theoretical model is developed and confirmed through PIC simulation. One ring-shaped beam and one co-axially propagating Gaussian beam drive wakefields in a preformed plasma volume filled with both electrons and positrons. The laser's ponderomotive force as well as the charge separation force in the front bucket of the first bubble are utilized to provide the transverse momenta of injected positrons and those positrons can be trapped by the focusing field and then accelerated by the wakefield. The simulation shows that a relatively high-charge, quasi-monoenergetic positron beams can be obtained.

Highlights

Intense relativistic positron beams are crucial for pair production in the field of fundamental physics [1] and violent high-energy astrophysical phenomena [2]
Since the concept of laser wakefield accelerator (LWFA) was first proposed in 1979 [5], many works have been done on electron acceleration using ultrafast laser systems [6,7,8,9,10,11,12,13,14,15,16,17,18,19]
The 2D simulation box corresponds to a physical volume of 120 μm × 160 μm, and is sampled by 20 cells per laser wavelength in the laser propagation direction and eight cells per wavelength in each transverse direction

Summary

Introduction

Intense relativistic positron beams are crucial for pair production in the field of fundamental physics [1] and violent high-energy astrophysical phenomena [2]. A stable method to generate intense, monoenergetic and fully tunable positron beams enables experimental study of gamma-ray bursts and black holes [3,4]. Bremsstrahlungbased high-energy positrons are usually produced in linear accelerators (LINACs) and synchrotron facilities via propagating the relativistic electron beams through thick, high-Z targets. The generation of sub-hundred MeV positrons has been experimentally demonstrated by hitting these electron beams on high-Z solid targets [23]. Positrons with high energy and small divergence can principally be achieved through laser-plasma acceleration [27,28,29,30,31]. A scheme for positron injection into these accelerators has yet been absent

Methods

Results

Conclusion