Silicon Sensor Development for the CMS Tracker Upgrade

The Large Hadron Collider at the European Council for Nuclear Research in Geneva is scheduled to undergo a major luminosity upgrade after its lifetime of ten years of operation around the year 2020, to maximize its scientific discovery potential. The total integrated luminosity will be increased by a factor of ten, which will dramatically change the conditions under which the four large detectors at the LHC will have to operate. The Compact Muon Solenoid, which has contributed to the recent discovery of a new, Higgs-like boson is one of them. Its innermost part -- the so-called tracker -- is a high-precision instrument that measures the created particles' trajectories by means of silicon detectors. With a total surface of more than 200 square-meters it is the largest device of its kind ever built. The increase in instantaneous luminosity in the upgraded LHC will lead to a dramatically increased track density at the interaction points of the colliding beams and thus also to a much more hostile radiation environment. As a consequence, the tracker of CMS will require a major upgrade and re-design of the sensors and read-out electronics as the presently installed components do not have sufficient granularity and radiation tolerance. An extensive research- and development campaign has therefore been started by the CMS collaboration to identify and assess suitable radiation-hard silicon substrates and sensor technologies that could be implemented in the future tracker. This thesis, carried out at CERN and the Vienna University of Technology will present aspects of this campaign, especially the investigation of a prototype structure called Multi-Geometry Silicon-Strip Detector or MSSD in laboratory measurements and tests with accelerator beams. It was designed to identify materials and strip geometries that will meet the stringent requirements for sensors in the outer part of the upgraded CMS tracker. After a brief introduction to the CMS experiment and silicon sensors in high-energy physics, the specific experimental setups and facilities that have been used during the research for this thesis will be described. The results obtained have been extensively analyzed, interpreted and compared to earlier work with the goal of submitting a recommendation for a suitable material and technology.