Direct Electron Acceleration using Circularly Polarized Laguerre-Gaussian Laser Pulses

Abstract

In this thesis, the generation and characterization of electron beams and electron-positron beams are investigated through two distinct studies, addressing the growing interest in advancing laser technology and its applications in laboratory astrophysics. The first study explores the concept of direct laser acceleration of electrons with ultra-intense lasers. Over the past two decades, laser-driven charged particle accelerations have garnered significant attention due to rapid advancements in laser technology and their wide range of applications in medical and fundamental research [1–3] . While the majority of laser particle acceleration schemes rely on plasma fields induced by high-intensity laser pulses [4–6], an alternative approach called direct laser acceleration (DLA) has recently gained attention [7–10]. The DLA scheme accelerates electrons directly with the field of the laser pulse. In this context, the first study in this thesis investigates the direct laser acceleration mechanism using Circularly Polarized Laguerre-Gaussian (CPLG) laser pulses. A comprehensive comparison of the properties of electron beams generated by antiparallel CPLG laser pulse and parallel CPLG laser pulse is performed with three-dimensional particle-in-cell simulations. The study reveals that collimated electron bunches with small divergence (<50 mrad) are formed with antiparallel CPLG laser pulses, while a diverging (>100 mrad) electron beam is formed with parallel CPLG laser pulses, emphasizing the differences in beam quality and field-induced acceleration in actual experiments. The second study focuses on the characterization of electron-positron plasma, which is a crucial experimental foundation for laboratory astrophysics [11–13], as it enables the replication of astrophysical scenarios in a controlled laboratory environment. The study presents the characterization of an electron-positron beam generated from the interaction of a multi-GeV electron beam with a lead plate using GEANT4 simulations [14]. The dependence of the positron beam size on driver electron beam energy and lead converter thickness is investigated in detail. It is demonstrated that a 5 GeV driver electron beam with 1 nC charge can generate a positron beam with a density of 10¹⁵–10¹⁶ cm⁻³ at one radiation length of lead, contributing to the understanding of laser-produced electron-positron plasma for laboratory astrophysics research. These two studies not only enhance the understanding of the generation and characteristics of electron beams and electron-positron beams but also provide valuable insights into their potential applications in laser acceleration technology and laboratory astrophysics.