21-27 March 2009
Prague
Europe/Prague timezone

Time Calibration of the ATLAS Tile Calorimeter

24 Mar 2009, 18:10
20m
Club D (Prague)

Club D

Prague

Prague Congress Centre 5. května 65, 140 00 Prague 4, Czech Republic
oral Online Computing Online Computing

Speaker

Mr Bjorn (on behalf of the ATLAS Tile Calorimeter system) Nordkvist (Stockholm University)

Description

The ATLAS Tile Calorimeter is ready for data taking during the proton-proton collisions provided by the Large Hadron Collider (LHC). The Tile Calorimeter is a sampling calorimeter with iron absorbers and scintillators as active medium. The scintillators are read out by wave length shifting fibers and PMTs. The LHC provides collisions every 25ns, putting very stringent requirements on the synchronization of the ATLAS triggering systems and the read out of the on-detector electronics. More than 99% of the read out channels of the Tile Calorimeter have been time calibrated using laser pulses sent directly to the PMTs. Timing constants can be calculated after corrections for i) propagation of trigger and clock signals, ii) differences in laser light paths to the different parts of the calorimeter. The calibration is implemented by i) programming delays in the on-detector electronics for groups of 6 channels, ii) residual deviations from perfect synchronization are stored in a database and used during the offline reconstruction of the Tile Calorimeter data. From the point of view of triggering and clock signals the Tile Calorimeter is divided into 4 independent sections. The time calibration has been used in each of the 4 sections, on the data taken during long ATLAS cosmic runs and during LHC beam time in September 2008. This has confirmed a timing uniformity of 2ns in each of the 4 calorimeter sections. The remaining delays between the 4 calorimeter sections have been measured i) using the laser pulses interleaved with cosmic trigger inside a global ATLAS run and ii) using real LHC events, and show consistent results. The main limitations on the precision of the time calibration are presented.

Primary author

Co-author

Dr Christophe Clement (Stockholm University)

Presentation Materials