Characterization of semiconductor detectors and test beams with high-rate telescopes for the Tracker upgrade of the CMS experiment

Abstract

In order to unveil the mysteries of the universe the high energy physicists will need to boost the world’s most powerful particle collider’s potential for discoveries. The High Luminosity Large Hadron Collider (HL-LHC) is an ongoing upgrade of the Large Hadron Collider (LHC) which aims at increasing the luminosity of the accelerator by a factor of 10, providing a better opportunity to observe rare processes and meliorating statistically marginal measurements. To face the challenges of the unprecedented p-p luminosity, the Compact Muon Solenoid (CMS) collaboration will need to cope with the aging of its present detector and to advance the methods used to isolate and measure accurately the products of the most significant collisions. To determine the conditions of the most important events it is critical to calculate the momentum of particles by tracking their paths through the magnetic field of the detector. The more curved the path of a particle, the less momentum it had. The charged particle paths are recorded in the innermost part of the CMS detector, the Tracker, by finding the positions of particles at several key points. The Tracker is capable of reconstructing the paths of high-energy muons, electrons and hadrons, as well as of registering tracks coming from the decay of the short-lived b quarks that will be used to study the differences between matter and antimatter. The position accuracy in the Tracker needs to be of the order of 10 micrometers, while its material to be able to withstand severe radiation. The upgraded Tracker detector for the HL-LHC era will be made entirely of silicon sensors, will have improved trigger capabilities and will be composed of two sub-detectors: a Pixel vertex detector occupying the inner region and an Outer Tracker (OT) consisting of microstrip modules. The wafers of all the microstrip prototype p-type silicon sensors which were studied in the framework of the CMS Phase-2 Tracker Upgrade contained half-moons with test structures. It was necessary to perform electrical characterization and irradiation tests on the test structures diced from these wafers, in order to determine the material quality and the behavior of the components on the test structures. The results of these tests are analyzed in this work. On the other hand, during the research and development period, tests performed under beam are a powerful way to examine the behavior of the silicon sensors in realistic conditions. The telescopes used in the past had a slow readout for the needs of the upgraded CMS experiment. New pixel telescopes were designed, built and commissioned for beam tests under the LHC nominal rate with prototype modules for the CMS Phase-2 Tracker Upgrade. The design and operation aspects of two such high-rate telescopes, as well as the results of the first beam tests with them, are also described in this dissertation.