CERN Accelerating science

ATLAS Slides
Report number	ATL-TILECAL-SLIDE-2017-542
Title	The ATLAS Tile Calorimeter experience with 10,000 readout photomultipliers operating since the start of the p-p collisions at LHC
Author(s)	Lazar, Hadar (University of Chicago, Enrico Fermi Institute) ; ATLAS Tile Collaboration
Corporate author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Submitted by	[email protected] on 16 Jul 2017
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	Laser II ; Tile Calorimeter ; Calibration ; Down Drift ; ATLAS detector
Abstract	The channels of TileCal, the hadron calorimeter of the Atlas experiment at the LHC, is readout with 8-stage fine-mesh PhotoMulTipliers (PMTs), a special version of the Hamamatsu model R5900. About 10000 PMTs are operating in TileCal. The PMT response stability allows to calibrate accurately the calorimeter and to achieve high performance of the energy reconstruction of the cells. Currently, no PMT replacement is foreseen before completion of the High Luminosity program of the LHC collider in the next decade. In this perspective, a number of measurements and tests are in progress to qualify the PMT robustness in terms of lifetime and response stability. Data from the Tile calibration procedure for the detector PMTs and from laboratory tests of spare PMTs are being analysed. Results on PMT failures, gain loss and quantum efficiency loss are presented. Analysis is focused on the study of the observed down-drift with time of the PMT response as a function of the integrated anode charge, and depending on the individual cell exposure to irradiation during the LHC operation. The multi-stage calibration system of Tile and the algorithms adopted to disentangle between gain and quantum efficiency loss are described, as well as the tests performed in dedicated test-benches.