  The CMS pixel detector is the innermost component of the CMS tracker
occupying the region around the centre of CMS, where the LHC beams are crossed,
between 4.3 cm and 30 cm in radius and 46.5 cm along the beam axis. It operates
in a high-occupancy and high-radiation environment created by particle
collisions. Studies of radiation damage effects to the sensors were performed
throughout the first running period of the LHC. Leakage current, depletion
voltage, pixel readout thresholds, and hit finding efficiencies were monitored
as functions of the increasing particle fluence. The methods and results of
these measurements will be described together with their implications to
detector operation as well as to performance parameters in offline hit
reconstruction.
