The LHCb Silicon Tracker commissioning and first data

The LHCb Silicon Tracker (ST) was installed in the LHCb detector and was successfully put into operation in summer 2008. The ST plays a crucial role in reconstructing the trajectories of charged particles. It consists of two silicon microstrip detectors, the Tracker Turicensis upstream of the LHCb dipole magnet and the Inner Tracker downstream of the magnet. Insights gained during the exciting commissioning phase, the problems encountered and their solutions are presented. The data collected during LHC injection tests in 2008 and 2009 allowed us to make a first measurement of the detector performance. The data is used to determine the spatial and time alignment of the ST. Furthermore, these tests have been extremely useful for tuning operational parameters of the different parts of the Silicon Tracker.