TY  - THES
AU  - Zeitler, Benno
TI  - Phase Space Linearization and External Injection of Electron Bunches into Laser-Driven Plasma Wakefields at REGAE
IS  - DESY-THESIS-2017-003
SN  - 1435-8085
PB  - Universität Hamburg
VL  - Dissertation
CY  - Hamburg
M1  - PUBDB-2017-00801
M1  - DESY-THESIS-2017-003
T2  - DESY-THESIS
SP  - 209
PY  - 2017
N1  - Dissertation, Universität Hamburg, 2016
AB  - Laser Wakefield Acceleration (LWFA) has the potential to become the next-generation accelerationtechnique for electrons. In particular, the large field gradients provided by these plasma-based acceleratorsare an appealing property, promising a significant reduction of size for future machines and user facilities.Despite the unique advantages of these sources, however, as of today, the produced electron bunches cannotyet compete in all beam quality criteria compared to conventional acceleration methods. Especially thestability in terms of beam pointing and energy gain, as well as a comparatively large energy spread ofLWFA electron bunches require further advancement for their applicability.The accelerated particles are typically trapped from within the plasma which is used to create the large fieldgradients in the wake of a high-power laser. From this results a lack of control and access to observing theactual electron injection – and, consequently, a lack of experimental verification. To tackle this problem,the injection of external electrons into a plasma wakefield seems promising. In this case, the initialbeam parameters are known, so that a back-calculation and reconstruction of the wakefield structureare feasible. Such an experiment is planned at the Relativistic Electron Gun for Atomic Exploration(Regae). Regae, which is located at Desy in Hamburg, is a small linear accelerator offering uniquebeam parameters compatible with the requirements of the planned experiment. The observations andresults gained from such an external injection are expected to improve the beam quality and stabilityof internal injection variants, due to the broadened understanding of the underlying plasma dynamics.Furthermore, an external injection will always be required for so-called staging of multiple LWFA-drivencavities. Also, the demonstration of a suchlike merging of conventional and plasma accelerators gives riseto novel hybrid accelerators, where the matured beam control achievable in conventional electron sourcesis combined with the huge gradients of a plasma booster stage. In this thesis, the concept of the externalinjection experiment at Regae is presented. The physical foundations are illustrated and combined intoan extensive start-to-end design study. Using the key constraints from this results, the required beam linedesign is developed.An injection into a plasma wave with the aim of diagnosing the accelerating field inevitably requireselectron bunches which are much shorter then the period of the plasma wavelength. This reference lengthis typically on the order of a few ten microns. The conventionally accelerated particle distribution musttherefore be compressed. At Regae the so-called ballistic bunching scheme is applied, leading to buncheswith a longitudinal extent of about 3 mm. Even better results can be obtained if nonlinearities arisingin the compression are compensated. A novel method to achieve this, based on the controlled beamexpansion, is the stretcher mode. It is developed and described in detail in the second part of this thesis.Simulations that verify the analytic model presented in the thesis suggest a possible decrease in bunchlength by a factor of ten and more compared to the design parameters of Regae. Electron bunch lengthsbelow 300nm, i.e., below one femtosecond (1 fs = 10−15 s) duration, can be produced. In addition, anenergy spread compensation leading to quasi mono-energetic beams can be achieved by this method.Importantly, the approach is not restricted to Regae or similar machines, but can be generalized to avariety of accelerators.
LB  - PUB:(DE-HGF)3 ; PUB:(DE-HGF)11
DO  - DOI:10.3204/PUBDB-2017-00801
UR  - https://bib-pubdb1.desy.de/record/317605
ER  -