Clock Distribution and Readout Architecture for the ATLAS Tile Calorimeter at the HL-LHC

The Tile Calorimeter (TileCal) is one detector of the ATLAS experiment at the large hadron collider (LHC). TileCal is a sampling calorimeter made of steel plates and plastic scintillators which are readout using approximately 10000 photomultipliers tubes. In 2024, the LHC will undergo a series of upgrades toward a high luminosity LHC (HL-LHC) to deliver up to 7.5× the current nominal instantaneous luminosity. The ATLAS Tile Phase II Upgrade will accommodate detector and data Acquisition (DAQ) system to the HL-LHC requirements. The detector electronics will be redesigned using a new clock distribution and readout architecture with a full-digital trigger system. After the Long Shutdown 3 (2024-2026), the on-detector electronics will transfer digitized hadron calorimeter data for every bunch crossing (~25 ns) to the Tile PreProcessors (TilePPr) in the counting rooms with a total data bandwidth of 40 Tb/s. The TilePPrs will store the detector data in pipeline memories to cope with the new ATLAS DAQ architecture requirements and will interface with the front-end link exchange system and the first trigger level. The TilePPr boards will distribute the sampling clock to the on-detector electronics for synchronization with the LHC clock using high-speed links configured for fixed and deterministic latency. The upgraded readout and clock distribution strategy were fully validated in a demonstrator system using prototypes of the upgraded electronics in several test beam campaigns between 2015 and 2018.