Ph.D. Theses

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2019-11-13
09:49
OpenAccess [PUBDB-2019-04190] Book/Report/Dissertation / PhD Thesis

Characterization of Ultrashort Electron Bunches at the SINBAD-ARES Linac
[DESY-THESIS-2019-026]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 176 pp. () [10.3204/PUBDB-2019-04190] = Dissertation, Universität Hamburg, 2019  GO
The generation of ultrashort electron bunches is an active area of research in accelerator physics. A key application of such bunches is the injection into novel accelerators with high-frequency accelerating fields, such as laser-wakefield plasma accelerators or dielectric laser accelerators. [...]
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2019-11-12
16:00
[PUBDB-2019-04176] Dissertation / PhD Thesis

Nuclear Cascades and Neutrino Production in the Sources of Ultra-High Energy Cosmic Ray Nuclei
Humboldt-Universität zu Berlin 165 pp. () [10.18452/20448] = Dissertation, Humboldt University, 2019  GO
Der Ursprung ultra-hochenergetischer kosmischer Strahlung (UHECRs) ist eine der wichtigsten offenen Fragen der Astrophysik. Gammastrahlenblitze (GRBs) galten als potentielle Quellen, da sie zu den energetischsten Ereignissen im Universum zählen. [...]
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2019-11-12
15:52
[PUBDB-2019-04175] Dissertation / PhD Thesis

Blazars as Sources of Neutrinos and Ultra-high-energy Cosmic Rays
Humboldt-Universität zu Berlin 166 pp. () [10.18452/20610] = Dissertation, Humboldt University, 2019  GO
Der Ursprung ultra-hochenergetischer kosmischer Strahlung (UHECRs) ist immer noch unbekannt. Neutrinoteleskope wie IceCube messen einen Fluss hochenergetischer astrophysikalischer Neutrinos, dessen erwarteter Ursprung Wechselwirkungen kosmischer Strahlung (CR) ist. [...]
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2019-11-12
10:23
[PUBDB-2019-04144] Dissertation / PhD Thesis

Molecular-Frame Angularly-Resolved Photoelectron Spectroscopy
Hamburg 1-196 () = Dissertation, Universität Hamburg, 2019
One of the big technical and scientific challenges today is to accomplish the ultimate dreamof filming chemical reactions with atomic spatial and temporal resolution and recording themolecular movie. Important prerequisites toward this goal are, on the one hand, methodsto create cold, controlled molecular samples and, on the other hand, imaging techniquesthat combine the required spatial and temporal resolution. [...]
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2019-11-01
14:59
OpenAccess [PUBDB-2019-03861] Book/Report/Dissertation / PhD Thesis

Acceleration and Phase Space Manipulation of Relativistic Electron Beams in Nano- and Micrometer-Scale Dielectric Structures
[DESY-THESIS-2019-025]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 215 pp. () [10.3204/PUBDB-2019-03861] = Dissertation, Universtät Hamburg, 2019  GO
This thesis is about simulations, proof-of-principle experimental setups and first test experiments for new ultra-compact particle accelerators based on dielectric structures. Due to the high damage threshold of nano- and micrometer-scale dielectrics in the optical regime, accelerating fields on the order of GV/m can be achieved. [...]
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2019-10-21
15:53
OpenAccess [PUBDB-2019-03713] Book/Report/Dissertation / PhD Thesis
et al
Demonstrating High Transformer Ratio Beam-Driven Plasma Wakefield Acceleration
[DESY-THESIS-2019-024]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY THESIS 197 pp. () [10.3204/PUBDB-2019-03713] = Dissertation, Universität Hamburg, 2019  GO
In this work, plasma wakefield acceleration with high transformer ratios, i.e. highratios between acceleration of witness particles to deceleration of driver particles, is investigated experimentally.Particle-beam-driven plasma wakefield acceleration (PWFA) is one of the primecandidates for future compact accelerator technologies. [...]
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2019-10-15
14:57
OpenAccess [PUBDB-2019-03677] Dissertation / PhD Thesis

Precision measurement of the top quark pair production cross section at $\sqrt{s}$ = 13 TeV with the CMS detector
1 - 138 () [10.3204/PUBDB-2019-03677] = Dissertation, Hamburg University, 2018  GO
This work presents several measurements of the inclusive top pair production cross sectionat a center of mass energy of√s = 13 TeV with the CMS detector. The cross section ismeasured using several data sets collected by the CMS detector in 2015 and 2016. [...]
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2019-10-01
16:19
OpenAccess [PUBDB-2019-03551] Book/Report/Dissertation / PhD Thesis

Development of a compact hard X-ray split-and-delay line for studying ultrafast dynamics at free electron laser sources
[DESY-THESIS-2019-023]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 140 pp. () [10.3204/PUBDB-2019-03551] = Dissertation, Universität Hamburg, 2019  GO
The study of condensed matter dynamics on ultrafast timescales is one of the key topics in modern material science research. Hard X-ray free-electron laser sources with extreme peak brightness and ultra short pulses provide excellent conditions for studying ultrafast dynamics in the time domain by employing such techniques as X-ray pump-probe spectroscopy or X-ray photon correlation spectroscopy. [...]
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2019-09-16
14:35
OpenAccess [PUBDB-2019-03351] Book/Report/Dissertation / PhD Thesis

Parametric Waveform Synthesis
[DESY-THESIS-2019-021]
Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-THESIS 172 pp. () [10.3204/PUBDB-2019-03351] = Dissertation, Universität Hamburg, 2019  GO
The coherent synthesis of pulses from Optical Parametric Amplifiers (OPAs) offers the possibility to realize field-controlled electromagnetic waveforms with sub-cycle durations, widely scalable in energy and spectral bandwidth.Here we demonstrate a fully functional prototype of a mJ-level two channel parametric waveform synthesizer, which is ready to be upgraded to three channels. The synthesized field, whose bandwidth covers more than 2 octaves, from ~500 nm to ~2200 nm, can be compressed to a non-sinusoidal sub-cycle waveform close to the transform-limit.The long term stable operation of such a complex laser source is achieved, for the first time, by means of a sophisticated optical and mechanical design of the whole OPA system, along with targeted improvements made to the commercial pump laser.A new seeding scheme based on multiple supercontinua, further scalable to the mid-IR, leads to excellent phase stability among the different OPA channels and to a simplified dispersion management scheme.A detailed study, both theoretical and experimental, of the couplings among different pulse parameters during the parametric amplification, unveiled novel details of the Carrier-Envelope-Phase (CEP) stabilization process via OPA, and guided the design of the CEP-controlled seeding front-end.A simplified two-dimensional spectral shearing interferometry setup, where the ancillary pulses are obtained by spectral filtering the pump pulses, has been developed to easily characterize the spectral phase of the ultrabroadband pulses from each channel, overcoming the limitation of second-harmonic-based methods.Furthermore, ad-hoc nonlinear optical techniques have been deployed to observe the most relevant synthesis parameters such as the CEP of the seeding pulses and the relative phase among the different channels outputs. [...]
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2019-08-30
14:05
OpenAccess [PUBDB-2019-03157] Dissertation / PhD Thesis

The magnetic properties of ultrathin Cobalt multilayers symmetrically and antisymmetrically sandwiched between layers of platinum and iridium
223 pp. () [10.3204/PUBDB-2019-03157] = Dissertation, Universität Hamburg, 2018  GO
This thesis deals with a systematic study of magnetic properties, i.e. saturation magnetization, exchange stiffness, anisotropy, interlayer exchange coupling, and average domains size, of ultrathin Co-based multilayer systems. [...]
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