Becker, Stefan (2010): Dynamics and Transport of LaserAccelerated Particle Beams. Dissertation, LMU München: Faculty of Physics 

PDF
Becker_Stefan.pdf 16MB 
Abstract
The subject of this thesis is the investigation and optimization of beam transport elements in the context of the steadily growing field of laserdriven particle acceleration. This cumulative thesis introduces to the theoretical framework of the elements and presents the results via corresponding publications. The first topic is the examination of the free vacuum expansion of an electron beam at high current density. Unlike in the case of conventional acceleration, laser acceleration yields charge densities which are comparatively high at lower energies. It could be shown that particle tracking codes which are commonly used for the calculation of space charge effects will generate substantial artifacts in the regime considered here. The artifacts occurring hitherto predominantly involve insufficient prerequisites for the Lorentz transformation, the application of inadequate initial conditions and non negligible retardation artifacts. A part of this thesis is dedicated to the development of a calculation approach which uses a more adequate ansatz calculating space charge effects for laseraccelerated electron beams. It can also be used to validate further approaches for the calculation of space charge effects. The next elements considered are miniature magnetic quadrupole devices for the focusing of charged particle beams. Invented in 1980 by Halbach, miniature permanent magnet quadrupoles yield field gradients at least a factor two higher than superconducting quadrupole devices. General problems involved with their miniaturization concern distorting higher order field components. If these distorting components cannot be controlled, the field of applications is very limited. In this thesis a new method for the characterization and compensation of the distorting components was developed, which might become a standard method when assembling these permanent magnet multipole devices. Consequently, the field where these devices are applicable could be broadened. The newly developed characterization method has been validated at the Mainz Microtron (MAMI) electron accelerator. Now that we can ensure optimum performance, the first application of permanent magnet quadrupole devices in conjunction with laseraccelerated ion beams is presented. The experiment was carried out at the ZPetawatt laser system at Sandia National Laboratories. A Free Electron Laser (FEL) delivers coherent photon beams at higher energies than what can be reached by conventional laser systems. A promising application for laseraccelerated electron beams is the FEL in a universityscale size. The first discussion of all relevant aspects concerning a laser driven FEL is presented. The operation of an FEL depends on many factors, among which is the average electron beam size while propagating through the undulator. The undulator length could be reduced significantly if the average beam size can be reduced. This goal motivates the development of a new undulator concept, based on miniature magnetic quadrupoles, which is presented here. This quadrupole undulator yields strong intrinsic focusing properties which allow to keep the electron beam at a comparatively small and constant size over a long propagation range. The experimental realization of a compact FEL involves the first step of building a test undulator with a short undulator period length. This undulator device was assembled and experiments aiming at undulator radiation have been carried out at the MAMI electron accelerator facility in the course of this thesis. The investigations presented in this thesis mark important development steps on the route towards many applications of laseraccelerated particle beams. Especially laserdriven compact FreeElectronLasers are an attractive alternative to costly largescale conventional facilities.
Item Type:  Thesis (Dissertation, LMU Munich) 

Subjects:  600 Natural sciences and mathematics 600 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date Accepted:  19. April 2010 
1. Referee:  Sauerbrey, Roland 
Persistent Identifier (URN):  urn:nbn:de:bvb:19114449 
MD5 Checksum of the PDFfile:  d665d457dd7f8f34a70058f6e151ce8e 
Signature of the printed copy:  0001/UMC 18540 
ID Code:  11444 
Deposited On:  28. Apr 2010 09:30 
Last Modified:  16. Oct 2012 08:37 