Irradiation Studies and Design Optimization of the ATLAS Tile Calorimeter for the High-Luminosity LHC

Abstract

The Tile Calorimeter (TileCal) is a sampling hadronic calorimeter covering the central region of the ATLAS experiment at the CERN Large Hadron Collider (LHC). It employs steel as the absorber material and plastic scintillators as the active medium. The High-Luminosity LHC (HL-LHC), scheduled to start operation in 2030, will deliver instantaneous luminosities significantly exceeding the baseline LHC design, imposing more stringent requirements on detector readout and trigger systems. Consequently, TileCal has to be capable of reliable operation under increased radiation levels and very high particle flux, while maintaining full compatibility with the upgraded ATLAS trigger architecture. During the Long Shutdown period (2026-2030), the TileCal readout electronics will be entirely replaced with radiation-tolerant systems designed to handle data rates approximately an order of magnitude higher than those of the baseline LHC configuration. The photomultiplier tubes (PMTs) in the most highly irradiated regions will also be replaced with improved devices exhibiting enhanced stability and radiation tolerance. To meet these challenges, the system design has been correspondingly optimized to ensure improved performance, efficiency and robustness in high-radiation environments, and an extensive irradiation testing program has been carried out. This contribution presents the resulting design developments of the TileCal system, together with the results obtained from the irradiation tests.