Bachelor Theses

This thesis studies the reconstruction of top quark-antiquark (t¯t) pairs in the dilepton decay channel, where both top quarks decay leptonically and two neutrinos escape detection. Since the event kinematics are underconstrained, the Sonnenschein algorithm, a fully analytical method used by the CMS and ATLAS experiments at the LHC, where quark-antiquark pairs of the heaviest elementary particle are produced in proton-proton collisions, is applied. [...]

The Large Hadron Collider will be upgraded to extend its lifetime and improve various components. With the upgrade to the High-Luminosity-LHC the instantaneous luminosity will increaseto 5 · 1034 cm−2s−1 and the total integrated luminosity to at least 3000 fb−1. [...]

The outer tracker of the Compact Muon Solenoid (CMS) Detector will be upgraded as part of the upgrade of the Large Hadron Collider (LHC) to the High-Luminosity LHC.The Tracker Endcap Double-Discs (TEDD), that are part of the outer tracker are built and integrated with modules at DESY. The CMS detector and with it the TEDD will be cooled to evacuate the generated heat of the modules, to minimize their leakage current due to the heavy irradiation from the passing through particles and avoid thermal runaway. [...]

The medium temperature heat treatment of superconducting radio frequency cavities is investigated to asses their use in an upgrade of the European X-ray Free ElectronLaser. For the medium temperature heat treatment, which alters the cavity’s surface, the question is, which influences on the performance of cavities do exist. [...]

The increasing demand for high-performance superconducting radiofrequency (SRF) cavities in particle accelerators,especially in free electron lasers, has led to intensified research on optimizing cavity treatments. One promisingrecent development is the application of medium temperature heat treatments, which are typically performed at250 ◦C - 350 ◦C in a vacuum furnace for several hours. [...]

A screening of oxygen profiles in mid-T treated SRF cavities is crucial, in order to infer physical correlations between the microscopic cavity lattice and cavity performance – a problem concerning acceleration physicists for years. This thesis provides an analysis of oxygen diffusion profiles for three differently treated samples: Two mid-T baked and the third with the standard EuXFEL recipe. [...]

The research on radiation therapy for cancer treatment is of the highest importance to society, ascancer is a leading cause of death. Conventional radiation therapy is conducted with X-rayradiation; however, new treatments are being researched using other types of ionizing radiationto deliver radiation doses more precisely to tumours while sparing healthy tissue and overcomingradioresistant cancers [...]

The fact that some materials orient themselves in highly ordered structures and thusacquire special properties has been the subject of research for years. These high-orderstructures can be produced by top-down methods such as lithography or by bottom-upgrowth from individual particles to smaller agglomerates or monolayers. [...]

For the examination of human tooth enamel, the FIB-SEM (Focused Ion Beam -Scanning Electron Microscop) is used. Layers of the tooth are removed. [...]