Ph.D. Theses

Nowadays particle detector technology is taking big steps forwards and new devices dedicated to particle physics show very high performance. Particularly the semi-conductor detectors have advanced significantly and are used for tracking purposes in the A Toroidal LHC ApparatuS (ATLAS) experiment at CERN thanks to their excellent spacial resolution: the compact size of the silicon and its high granularity allow to reach a precision measurement of few tens of microns.This thesis is focused on the upgrade of the ATLAS tracking detector required for the High Luminosity Large Hadron Collider (HL-LHC), starting in 2027. [...]

With the fast technological developments of our time often new possibilities arise to gain a deeperscientific understanding of complex processes, may these be of biological, chemical or physicalnature, and materials. In natural sciences, X-ray and electron microscopy is indispensable tohelp uncovering these scientific backgrounds. [...]

The nature of dark matter is one of the biggest open questions in modern physics. While dark matter accountsfor roughly 25% of the energy density in the Universe, its particle nature remains unknown so far. [...]

The project's main goal is to design tailored post-process heat treatments for four LPBF high-end alloys (AlSi10Mg, AlSi7Mg, Ti6Al4V ELI, Inconel 718) that are widely used in the Aerospace, Healthcare, and Energy industry. The precondition for a successful design of the tailored heat treatment is the guarantee that mechanical property standards for the Aerospace, Healthcare, and Energy industry are met at any time. [...]

The advent of X-ray free-electron lasers (XFELs) over the past decade, providing ultraintense femtosecond X-ray pulses, offers novel opportunities formolecular structure investigations. By now, most of the established approachesrevolve around diffractive imaging schemes with crystalline samples, whereelectronic and nuclear radiation damage, caused by the X-rays, must be avoidedto achieve the highest possible spatial resolution. [...]

Magnetite ($\text{Fe}_3\text{O}_4$), one of the first known magnetic materials, has multiple applications as for example as a catalyst or catalyst component. Magnetite nanoparticles are used as contrast agents in medicine or building blocks in novel hierarchical materials with outstanding mechanical properties. [...]

This thesis presents the total charm cross section measurement in the full kinematic phase space of pp collisions at the LHC. It was performed using open data (2010) from the CMSexperiment at a center-of-mass energy of 7 TeV due to its special low p$_{\mathrm{T}}$ tracking. [...]

AbstractA search for new heavy particles that decay into top quark-antiquark pairs ispresented using an integrated luminosity of 20.3 fb−1 of proton-proton collision datarecorded at a centre-of-mass energy of √s = 8 TeV with the ATLAS experiment atthe Large Hadron Collider. The analysis considers events with exactly one chargedlepton, missing transverse momentum and jets in the final state. [...]

The structure and composition of niobium, the current state-of-the-art material for superconductingradio-frequency (SRF) cavities, are of extreme importance in understandingthe operation behaviour of cavities. In recent years, the use of nitrogen to improve this behaviourhas been widely studied. [...]

This thesis focuses on the fundamental understanding of different catalytic reactions at the interface between a solid catalyst and a liquid reactant phase. To this end, both in situ and operando experiments, monitored by synchrotron X-ray diffraction techniques as well as infrared spectroscopy based surface science model studies, were performed. [...]