Upgrade of the ATLAS Tile Calorimeter for the High luminosity LHC

The hadronic calorimeter of ATLAS (TileCal) will undergo a complete replacement of its on-detector and off-detector electronics for the high luminosity programme of the LHC in 2024. The calorimeter signals from all PMTs will be digitized and sent directly to the off-detector electronics, where the signals are reconstructed and feed into the ATLAS first level trigger at a rate of 40 MHz. This will provide better precision and a finer granularity for the trigger system and will allow the development of more efficient trigger selections. To validate this free-running read-out architecture we plan to insert into ATLAS at the end of 2015 one demonstrator prototype. The demonstrator is an hybrid module containing the new electronics but also providing the analog trigger signals to be compatible with the present system. At the current stage of development three different options are being investigated for the upgrade of the front-end electronic and we plan extensive test beam and simulation studies to select the best option.