Performance Studies of Silicon Strip Sensors for the Phase-II Upgrade of the CMS Tracker

In 2025, the LHC (Large Hadron Collider) will be upgraded to the High-Luminosity LHC. The luminosity will be enhanced by a factor of 5 to 10, up to 10^35 cm^-2s^-1. This leads to new challenges for experiments such as the Compact Muon Solenoid (CMS), which is already afflicted by aging effects (radiation damages). Therefore the currently installed silicon sensors of the track detector ("Tracker") have to be replaced, furthermore to carry out higher radiation doses (through raised collision rates) and increased data rates. The prototypes of the new sensors are provided by the vendors Infineon and Hamamatsu. These have to be qualified for application by institutes like the Institute of High Energy Physics (HEPHY). For this diploma thesis, I did testbeam measurements on these sensors using protons (64 to 252MeV) at MedAustron and electrons (5.6 GeV) at Deutsches Elektronen-Synchrotron (DESY), analyzed the data and utilized performance and quality evaluation. These methods include IV characteristics, noise contribution, cluster analysis, beam profile measurement, efficiency and energy measurements. In preparation for the testbeams, I tested new trigger scintillators to determine dark rates and efficiency and the strip sensor system using a radioactive source and a laser test stand at the HEPHY. At the MedAustron’s first testbeam, high particle rates (up to 10^10/s) exceeded the sensor system’s processing rate. Occupancy and pile-up effects dominated the signal and distorted measured energy depositions. During the testbeam, the bias voltage supply of the strip sensor showed compliance, leading to voltage drops. After changes made to the accelerator by MedAustron staff, lower particle rates (10^5/s) were available at the second testbeam. These actions, complemented by optimizations in the setup, lead to stable power supply and analysis showed excellent conformity of measured stopping power to reference data. Prospective testbeams require extensive preparations in terms of functionality tests, standardization and simulation in advance to identify design flaws. For achieving better energy resolution in future, well-defined particle rate control by MedAustron is essential, as well as high time-resolved monitoring the current consumption of the sensor. If there is a demand for low-energy testbeams, it is essential to analyze the non-linear gain behavior in the upper energy deposition range of the ALiBaVa system. Based on that, one may eventually extend the analysis software algorithm. Further procedures should cover protection against electromagnetic interference. Perhaps it will be possible to find an appropriate model to characterize electronic noise contribution to improve SNR.