Integrator Based Readout in Tile Calorimeter of the ATLAS Experiment

TileCal is the Barrel hadronic calorimeter of the ATLAS experiment at LHC/CERN. To equalize the response of individual TileCal cells with a precision better than 1% and to monitor the response of each cell over time, a calibration and monitoring system based on a Cs137 radioactive source driven through the calorimeter volume by liquid flow has been implemented. This calibration system relies on a dedicated readout chain based on slow integrators that read currents from the TileCal photomultipliers integrating over milliseconds during the calibration runs. Moreover, during the LHC collisions the TileCal integrator based readout provides the signal coming from inelastic proton-proton collisions at low momentum transfer. This is used to monitor in ATLAS the instantaneous luminosity as well as the response of all calorimeter cells during data-taking.