Abstract
The TileCal is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, with steel as absorber and plastic scintillators as active medium. The scintillators are read out by wavelength shifting fibres to PMTs at the back of each wedge-shaped calorimeter module. The analogue signals from the PMTs are amplified, shaped, and digitized on the detector every 25 ns, and stored on detector in digital pipeline buffers until a trigger decision is received. The data are then read out to the off-detector systems for further processing. The TileCal employs several calibration systems that, together with the collected collision data, provide the basis for response equalisation and monitoring at each stage of the readout path from scintillation light production to energy and time reconstruction. Furthermore, the calorimeter performance has been established with large samples of proton-proton collision data during LHC Run 1 and Run 2. The high-momentum isolated muons have been used to study and validate the electromagnetic scale, while the hadronic response has been probed with isolated hadrons. We present and summarise results of the calorimeter calibration and performance.
Highlights
All the different C factors shown in the equation represents the calibration constants
The calibration constants are provided by individual systems during the ATLAS operations:
We show the variations in the response of the most highly irradiated regular cells observed by Minimum Bias monitoring and Laser systems during the 2017 data taking period
Summary
The Cesium system is based on three moveable radioactive sources using a hydraulic control through a system of steel tubes. The Cs-137 sources move inside the calorimeter, emitting 0.662 MeV photons to illuminate the scintillators. Between Run 1 and Run 2, a new water storage system, lower pressure in the hydraulics, and more precise water level metering during the scans were installed to improve stability and safety of the operation. The precision of the system in a single typical cell is approximately 0.3%, and the variation of the Cs during Run 2 is 10% for the first radial layer, closest to the beam pipe, and less than 4% for the other two layers
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