Materials design of photocathodes for free electron lasers from first principles simulations
File(s)
Author(s)
Chang Lee, Victor
Type
Thesis
Abstract
This thesis is focused on the simulation of photoemission for the design of new photocathode materials for Free electron laser (FEL) applications. In order to understand and develop new photocathode materials, a photoemission model that simulates the quantum efficiency (QE) and the mean transverse energy (MTE) of the photoemitted electrons from first principles simulations of the electronic structure of a material is developed in this work. The model presented in this work extends the previous models of photoemission to include an explicit model of surfaces, finite temperature and the effects of an external electric field.
The photoemission model presented in this work is applied to simulations on different metallic surfaces and the results are compared to experimental measurements of MTE done by the ASTeC group at STFC with reasonable agreement. The computed QE is within the range of previously reported experimental values. Discrepancies between the computed and experimental workfunction observed in this work are studied from the perspective that a change in surface chemistry and composition can produce the observed change in workfunction.
The photoemission model presented in this work is applied to simulations on different metallic surfaces and the results are compared to experimental measurements of MTE done by the ASTeC group at STFC with reasonable agreement. The computed QE is within the range of previously reported experimental values. Discrepancies between the computed and experimental workfunction observed in this work are studied from the perspective that a change in surface chemistry and composition can produce the observed change in workfunction.
Version
Open Access
Date Issued
2021-07
Date Awarded
2021-12
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Harrison, Nicholas
Sponsor
Science and Technology Facilities Council (Great Britain)
Engineering and Physical Sciences Research Council
UK Research and Innovation
Grant Number
EP/L015277/1
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)