Commissioning, Calibration & Early Performance of the LHCb Scintillating Fibre Tracker

The LHCb detector has undergone a major upgrade for Run 3 of the LHC enabling it to operate at a five times higher instantaneous luminosity and to read out the entire detector at a frequency of 40 MHz, corresponding to the bunch crossing frequency of the LHC. The main tracking stations of the spectrometer were replaced by the Scintillating Fibre (SciFi) Tracker, a large, high granular tracking detector based on 250 $\mu$m scintillating fibres readout by arrays of silicon photomultipliers (SiPMs). The SiPM signals are processed and digitised by a custom ASIC at 40 MHz. Further digital electronics perform clustering and data compression before sending the data via optical links to the data acquisition system. This thesis describes the LHCb SciFi Tracker and the commissioning of its front-end electronic. It highlights the calibration of the frontend ASICs' detection thresholds, a crucial task to ensure the detector's optimal performance. It is shown that, following the calibration of the detection thresholds, the detector achieves a hit detection efficiency of 99 % and a single hit resolution of <100 $\mu$m while maintaining a sufficiently low noise rate.