Performance of the ATLAS/LHC Tile Calorimeter Plastic Scintillators

The Tile Calorimeter is the central hadronic calorimeter of the ATLAS detector at the LHC/CERN [1]. It is a sampling calorimeter that uses steel absorber interleaved with trapezoidal plastic scintillators as active material to measure the energy of particles coming from the LHC collisions. The light emitted by the scintillators is collected at the edges by wavelength-shifting (WLS) optical fibres and transported to readout photomultiplier tubes for the signal measurement. The scintillators are 3 mm thick and are polystyrene-based doped with 1.5% PTP and 0.05% POPOP. These were custom manufactured by injection moulding to shape the different necessary sizes, ranging from 10 to 19 cm in height by 20 to 40 cm in width. In total, the calorimeter employs 460000 tile scintillators and 550000 WLS fibres. The initial light yield of the scintillators was around 70 photo-electrons/MeV, measured with electron beams. For the detector design, irradiation studies were also performed. This presentation reports the good performance of the calorimeter passed 13 years of installation and on the monitoring of the scintillators and WLS fibres degradation with dose exposure. 1. ATLAS Collaboration, “The ATLAS Experiment at the CERN Large Hadron Collider", J. Inst. 3(2008)S08003 (2008)