PoS - Proceedings of Science
Volume 340 - The 39th International Conference on High Energy Physics (ICHEP2018) - Parallel: Detector
ATLAS Calorimeter system: Run-2 performance, Phase-1 and Phase-2 upgrades
S. Stärz* on behalf of the ATLAS collaboration
*corresponding author
Full text: pdf
Published on: August 02, 2019
Abstract
The ATLAS detector was designed and built to study proton-proton collisions produced at the LHC at centre-of-mass energies up to 14 TeV and instantaneous luminosities up to $10^{34} \mathrm{cm}^{-2} \mathrm{s}^{-1}$. A liquid argon sampling calorimeter (LAr) is employed as electromagnetic calorimeter and hadronic calorimeter, except in the barrel region, where a scintillator-steel sampling calorimeter (TileCal) is used for the hadronic calorimeter.

ATLAS recorded $87 \mathrm{fb}^{-1}$ of data at a center-of-mass energy of 13 TeV between 2015 and 2017. The calorimetry system performed accordingly to its design values and played a crucial role in the ATLAS physics programme.

This contribution gives an overview of the detector operation, monitoring and data quality, as well as the achieved performance, including the calibration and stability of the energy scale, noise level, response uniformity and time resolution of the ATLAS calorimetry system. The upgrade projects of the ATLAS calorimeter system are presented.

An upgrade of the LAr trigger readout is necessary for Run-3, where luminosities around $\mathcal{L}~\approx~2-3~\times~10^{34}~\mathrm{cm}^{-2} \mathrm{s}^{-1}$ will be achieved, in order to keep a high signal efficiency. The electronics includes the LAr Trigger Digitizer front-end system that digitizes 34,000 channels at 40 MHz with transverse 12-bit precision after bipolar shaping and the back-end LAr Digital Processing system that computes the energy and time of the signals. Results of the system integration tests are presented along with the overall system design.

For the high luminosity phase of the LHC (HL-LHC), the luminosity will increase up to $\mathcal{L}~\approx~7.5~\times~10^{34} \mathrm{cm}^{-2} \mathrm{s}^{-1}$ leading to an average pile-up up to 200 interactions per bunch crossing. The electronics of both calorimeters has to be upgraded to cope with longer latencies of up to $35~\mathrm{\mu s}$ needed by the trigger system for such high pile-up levels.

For the Tile system, the photomultiplier signals will be digitized and transferred off-detector to the TileCal PreProcessors (TilePPr) for every bunch crossing, requiring a data bandwidth of 40~Tbps to read out the entire detector. The TilePPr will reconstruct, store and send the calorimeter signals to first level of trigger at a rate of 40 MHz. In parallel, the data samples will be stored in pipeline memories until the reception of the first-level trigger acceptance signal. The data of the selected events by the ATLAS central trigger system will be transferred to the ATLAS global Data AcQuisition (DAQ) system for further processing.

Test results of the first prototypes will be presented, along with design studies and simulations of the performance of the readout system.
DOI: https://doi.org/10.22323/1.340.0029
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