Advanced

Efficiency Enhancement Techniques for Free-Electron Lasers

Mak, Alan LU (2017)
Abstract (Swedish)
The central question addressed in this thesis is how to make the free-electron laser (FEL) more efficient. In recent years, coherent diffraction imaging provides an important motivation for efficiency enhancement. This is because a more efficient FEL process enables converting a larger fraction of the electron beam's power into optical power. By increasing the average optical power to the terawatt level, an x-ray FEL will open the door to single-shot, single-molecule imaging with a sufficiently high signal-to-noise ratio.

This thesis examines two techniques for efficiency enhancement, namely, undulator tapering and the phase jump method.

For undulator tapering, the well-established analytical model by Kroll, Morton and... (More)
The central question addressed in this thesis is how to make the free-electron laser (FEL) more efficient. In recent years, coherent diffraction imaging provides an important motivation for efficiency enhancement. This is because a more efficient FEL process enables converting a larger fraction of the electron beam's power into optical power. By increasing the average optical power to the terawatt level, an x-ray FEL will open the door to single-shot, single-molecule imaging with a sufficiently high signal-to-noise ratio.

This thesis examines two techniques for efficiency enhancement, namely, undulator tapering and the phase jump method.

For undulator tapering, the well-established analytical model by Kroll, Morton and Rosenbluth (KMR) is revisited and modified. With the aid of numerical simulations, it is demonstrated that the modified model results in a further enhancement in FEL efficiency beyond the original model.

For the phase jump method, a new physics model is developed to describe the energy extraction mechanism in the longitudinal phase space. The model reveals the possibility to extract energy from electrons outside the ponderomotive bucket, as well as the potential to increase the spectral purity by suppressing the synchrotron sidebands. (Less)
Abstract
The central question addressed in this thesis is how to make the free-electron laser (FEL) more efficient. In recent years, coherent diffraction imaging provides an important motivation for efficiency enhancement. This is because a more efficient FEL process enables converting a larger fraction of the electron beam's power into optical power. By increasing the average optical power to the terawatt level, an x-ray FEL will open the door to single-shot, single-molecule imaging with a sufficiently high signal-to-noise ratio.

This thesis examines two techniques for efficiency enhancement, namely, undulator tapering and the phase jump method.

For undulator tapering, the well-established analytical model by Kroll, Morton and... (More)
The central question addressed in this thesis is how to make the free-electron laser (FEL) more efficient. In recent years, coherent diffraction imaging provides an important motivation for efficiency enhancement. This is because a more efficient FEL process enables converting a larger fraction of the electron beam's power into optical power. By increasing the average optical power to the terawatt level, an x-ray FEL will open the door to single-shot, single-molecule imaging with a sufficiently high signal-to-noise ratio.

This thesis examines two techniques for efficiency enhancement, namely, undulator tapering and the phase jump method.

For undulator tapering, the well-established analytical model by Kroll, Morton and Rosenbluth (KMR) is revisited and modified. With the aid of numerical simulations, it is demonstrated that the modified model results in a further enhancement in FEL efficiency beyond the original model.

For the phase jump method, a new physics model is developed to describe the energy extraction mechanism in the longitudinal phase space. The model reveals the possibility to extract energy from electrons outside the ponderomotive bucket, as well as the potential to increase the spectral purity by suppressing the synchrotron sidebands. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr. McNeil, Brian, University of Strathclyde, Glasgow, United Kingdom
organization
publishing date
type
Thesis
publication status
published
subject
keywords
free-electron laser, accelerator physics, efficiency enhancement, undulator tapering, phase jump method, synchrotron radiation
pages
140 pages
publisher
Lund University, Faculty of Science, Department of Accelerator Physics, MAX IV Laboratory
defense location
The MAX III seminar room at the MAX IV Laboratory, Fotongatan 2, Lund
defense date
2017-06-15 13:00
ISBN
978-91-7753-305-4
language
English
LU publication?
yes
id
f92cc2d5-f2bc-4312-a230-ecb34d2c4f3f
date added to LUP
2017-05-11 15:37:06
date last changed
2017-06-08 12:17:32
@phdthesis{f92cc2d5-f2bc-4312-a230-ecb34d2c4f3f,
  abstract     = {The central question addressed in this thesis is how to make the free-electron laser (FEL) more efficient. In recent years, coherent diffraction imaging provides an important motivation for efficiency enhancement. This is because a more efficient FEL process enables converting a larger fraction of the electron beam's power into optical power. By increasing the average optical power to the terawatt level, an x-ray FEL will open the door to single-shot, single-molecule imaging with a sufficiently high signal-to-noise ratio.<br/><br/>This thesis examines two techniques for efficiency enhancement, namely, undulator tapering and the phase jump method.<br/><br/>For undulator tapering, the well-established analytical model by Kroll, Morton and Rosenbluth (KMR) is revisited and modified. With the aid of numerical simulations, it is demonstrated that the modified model results in a further enhancement in FEL efficiency beyond the original model.<br/><br/>For the phase jump method, a new physics model is developed to describe the energy extraction mechanism in the longitudinal phase space. The model reveals the possibility to extract energy from electrons outside the ponderomotive bucket, as well as the potential to increase the spectral purity by suppressing the synchrotron sidebands.},
  author       = {Mak, Alan},
  isbn         = {978-91-7753-305-4},
  keyword      = {free-electron laser,accelerator physics,efficiency enhancement,undulator tapering,phase jump method,synchrotron radiation},
  language     = {eng},
  pages        = {140},
  publisher    = {Lund University, Faculty of Science, Department of Accelerator Physics, MAX IV Laboratory},
  school       = {Lund University},
  title        = {Efficiency Enhancement Techniques for Free-Electron Lasers},
  year         = {2017},
}