Thesis

Advanced modelling of Free-Electron Lasers : unaveraged simulations, sub-wavelength effects, and superradiant pulses saturation

Downloadable Content

Download PDF
Creator
Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2025
Thesis identifier
  • T17206
Person Identifier (Local)
  • 201882454
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • This thesis presents the development and application of advanced computer simulationtechniques for the study of cavity-based Free-Electron Lasers (FELs). The researchintegrates the unaveraged 3D FEL simulation code Puffin with the Optical PropagationCode (OPC) to enable the modelling of broadband, high temporal-resolution cavityFELs. This novel approach allows for the translation of radiation field formats betweenPuffin and OPC, facilitating the simulation of a Regenerative Amplifier FEL operatingin the VUV range.Traditional simulation models for cavity-based FELs have averaged the optical fieldover an integer number of radiation wavelengths. This thesis, however, employs unaveraged simulation codes to model cavity-based FELs at the sub-wavelength scale.This enables the examination of effects such as Coherent Spontaneous Emission (CSE)from the electron beam and sub-wavelength cavity length detuning. The simulationsreveal that for small sub-wavelength detunings, the FEL can preferentially lase at thethird harmonic of the fundamental wavelength, suggesting new operational modes andpotential applications for cavity-based FELs.Additionally, a detailed study is conducted on the saturation mechanism of a singlesuperradiant spike of radiation in an FEL. Using a one-dimensional model developedwith Puffin, the thesis demonstrates the sub-wavelength evolution of spike radiationand electron dynamics, leading to a highly non-linear saturation process. The studyprovides insights into the broad spectrum and high power of the saturated spike, with aproposed saturation mechanism validated by numerical results and simplified analysisof the 1D FEL equations.The combined use of Puffin and OPC codes represents a significant advancementin FEL simulation, enabling the exploration of unaveraged FEL and optical effectsfor the first time. This research not only enhances the understanding of fundamentalFEL processes but also opens new avenues for further exploration and technologicaldevelopment in the field of Free-Electron Lasers.
Advisor / supervisor
  • McNeil, B.
Resource Type
DOI
Funder

Relations

Items

Thumbnail Title Date Uploaded Visibility Actions
file details PDF of thesis T17206 2025-03-05 Public Download