Characterisation and commissioning of the LHCb VELO detector

The LHCb detector is a one-armed spectrometer at the Large Hadron Collider. It has been designed to look for physics beyond the Standard Model through high precision measurements of CP-violation in the B-system and through the detection of rare B-decays. The success of LHCb relies heavily on its vertex detector, the VELO (VErtex LOcator), which will be used to trigger on B decay vertices and reconstruct them with micrometre accuracy. While small in size, comprising just 84 sensors, the VELO construction poses special challenges due to the high accuracy required and the proximity to the LHC beams. The detector will be required to operate under vacuum and will be exposed to high radiation levels. The first section of the thesis gives a brief introduction to the LHCb detector and the physics programme of the LHCb collaboration. The following sections review the VELO design and give and in-depth report on measurements of the detector performance based on data collected in beam tests. Topics covered are hit resolution, Signal-to-Noise ratio, sensor bias dependent cluster positions and vertex reconstruction performance. The last section of the thesis reports on the commissioning of the VELO.