@phdthesis{Swirski2021,
  author    = {Swirski, Thorben},
  title     = {Studies on the Effect of Gas Contaminations in Micromegas Detectors and Production of Micromegas Detectors for the New Small Wheel of the ATLAS Detector},
  doi       = {10.25972/OPUS-24640},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-246405},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {This work consists of two parts. On the one hand, it describes simulation and measurement of the effect of contaminations of the detector gas on the performance of particle detectors, with special focus on Micromegas detectors. On the other hand, it includes the setup of a production site for the finalization of drift panels which are going to be used in the ATLAS NSW. The first part augments these two parts to give an introduction into the theoretical foundations of gaseous particle detectors.},
  subject      = {Gasionisationsdetektor},
  language  = {en}
}
@phdthesis{Sidiropoulou2018,
  author    = {Sidiropoulou, Ourania},
  title     = {Characterization of the ATLAS-type Micromegas Detectors},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-167323},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2018},
  abstract  = {Micromegas are parallel-plate gaseous detectors with micro-pattern readout structures that are able to measure precisely and efficiently at high particle rates. Their difference with respect to other gaseous detectors is that the space in which particles ionise the gas and create electrons is separated from the region in which these electrons are multiplied (or amplified) by a thin metallic mesh. In the ionisation region, typically a few mm thick, a moderate field of a few hundred V/cm is applied. The amplification region with a homogeneous electrical field of 40--50~kV/cm is only 100--150~\$\upmu\$m thick. The latter guarantees that the positive ions produced in the amplification process are rapidly evacuated and the possibility to build up space charge at high rate is reduced. Critical in micromegas detectors are sparks in the thin amplification region in the presence of the high electrical field. This problem was solved in 2011 by introducing a spark protection scheme. It consists of a layer of resistive strips on top of the readout strips, separated from the latter by a thin insulation layer. Micromegas with the spark protection scheme were selected as instrumentation of the first ATLAS forward muon station (NSW) in the upgrade of the ATLAS detector for the operation of the Large Hadron Collider (LHC) at high luminosity (HL-LHC), expected for 2026. The main subjects of this thesis are: the characterisation of the first micromegas quadruplet prototypes for the NSW detectors; the characterisation of the materials used in the spark-protection system; and the study of the influence of the mesh distance holders (pillars) on the detector performance. The thesis starts with a brief introduction into the LHC and ATLAS projects, followed by a chapter that explains the reason for the upgrade of the ATLAS muon system and shows the layout of the NSW. The first of the three main chapters covers the construction and the characterisation of the first two prototypes for the NSW detectors. These detectors comprise four detection layers and have the same mechanical structure as the NSW detectors. The mechanical precision as well as the homogeneity of the detector response are discussed. The latter has been measured using X-rays and cosmic rays. The spatial resolution that can be achieved with these detectors precision has been measured at the MAMI accelerator at Mainz with low-energy electrons. The chapter is completed by a section that describes the successful integration of a data acquisition system (DAQ) into the official ATLAS DAQ system that was required for an initially planned installation of one of the prototypes on the existing Small Wheel. The next chapter presents a study of the influence of temperature and humidity changes on the resistive strips used in the spark protection system. In addition the long-term stability of the resistive material has been measured accumulating charge equivalent to 100 years of operation in the HL-LHC and exposing the samples to intense gamma irradiation equivalent to 10 years of HL-LHC operation. The third part covers the impact of the mesh distance holders (pillars) on the performance of the detector. This study has been performed with a 10 x 10 cm\$^2\$ bulk-micromegas with two different pillar shapes. Both 5.9 keV gammas from a \$^{55}\$Fe and 8 keV X-rays from a Cu target were used. In this context also the electrostatic charge-up of the detector is discussed. In the Appendices one finds a summary of the fundamental physics relevant for gaseous detectors as well as some supporting material for the topics covered in the main part of the thesis.},
  subject      = {ATLAS <Teilchendetektor>},
  language  = {en}
}
@phdthesis{Kuger2017,
  author    = {Kuger, Fabian},
  title     = {Signal Formation Processes in Micromegas Detectors and Quality Control for large size Detector Construction for the ATLAS New Small Wheel},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-152495},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {The Micromegas technology is one of the most successful modern gaseous detector concepts and widely utilized in nuclear and particle physics experiments. Twenty years of R \& D rendered the technology sufficiently mature to be selected as precision tracking detector for the New Small Wheel (NSW) upgrade of the ATLAS Muon spectrometer. This will be the first large scale application of Micromegas in one of the major LHC experiments. However, many of the fundamental microscopic processes in these gaseous detectors are still not fully understood and studies on several detector aspects, like the micromesh geometry, have never been addressed systematically. The studies on signal formation in Micromegas, presented in the first part of this thesis, focuses on the microscopic signal electron loss mechanisms and the amplification processes in electron gas interaction. Based on a detailed model of detector parameter dependencies, these processes are scrutinized in an iterating comparison between exper- imental results, theory prediction of the macroscopic observables and process simulation on the microscopic level. Utilizing the specialized detectors developed in the scope of this thesis as well as refined simulation algorithms, an unprecedented level of accuracy in the description of the microscopic processes is reached, deepening the understanding of the fundamental process in gaseous detectors. The second part is dedicated to the challenges arising with the large scale Micro- megas production for the ATLAS NSW. A selection of technological choices, partially influenced or determined by the herein presented studies, are discussed alongside a final report on two production related tasks addressing the detectors' core components: For the industrial production of resistive anode PCBs a detailed quality control (QC) and quality assurance (QA) scheme as well as the therefore required testing tools have been developed. In parallel the study on micromesh parameter optimization and production feasibility resulted in the selection of the proposed mesh by the NSW community and its full scale industrial manufacturing. The successful completion of both tasks were im- portant milestones towards the construction of large size Micromegas detectors clearing the path for NSW series production.},
  subject      = {Gasionisationsdetektor},
  language  = {en}
}
@phdthesis{Weber2016,
  author    = {Weber, Stefan},
  title     = {Simulation Studies on the New Small Wheel Shielding of the ATLAS Experiment and Design and Construction of a Test Facility for Gaseous Detectors},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-133084},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2016},
  abstract  = {In this thesis two main projects are presented, both aiming at the overall goal of particle detector development. In the first part of the thesis detailed shielding studies are discussed, focused on the shielding section of the planned New Small Wheel as part of the ATLAS detector upgrade. Those studies supported the discussions within the upgrade community and decisions made on the final design of the New Small Wheel. The second part of the thesis covers the design, construction and functional demonstration of a test facility for gaseous detectors at the University of W{\"u}rzburg. Additional studies on the trigger system of the facility are presented. Especially the precision and reliability of reference timing signals were investigated.},
  subject      = {Teilchendetektor},
  language  = {en}
}