Commissioning of the Laser II of the TileCal Calorimeter CERN summer student report

The Tile calorimeter is the central hadronic calorimeter of ATLAS. It is a sampling calorimeter allowing the detections of hadrons, jets and hadronic decays of tau leptons contributing also to the missing transverse energy determination. It includes about 10k PhotoMultipliers (PMT’s) to detect the light produced by particles showering in the detector. The role of the Laser II system is to control the stability of the gains of such PMT’s. Before the installation of the laser in the pit to replace the old system a long commissioning phase has been done. My task was to participate to the measurements and to the analysis of the collected data.