The Demonstrator of the HL-LHC ATLAS Tile Calorimeter

The High Luminosity Large Hadron Collider (HL-LHC) has motivated R&D to upgrade the ATLAS Tile Calorimeter. The new system consists on an optimized analogue design engineered with selected radiation-tolerant COTS and redundancy layers to avoid single points of failure. The design will provide better timing, improved energy resolution, lower noise and less sen-sitivity to out-of-time pileup. Multiple types of FPGAs, CERN custom rad-hard ASICs (GBTx), and multi-Gbps optical links are used to distribute LHC timing, read out fully digital data of the whole TileCal, transmit timing and calibrated energy per cell to the Trigger system at 40 MHz, and provide triggered data at 1 MHz. To test the upgraded electronics in real ATLAS conditions, a hybrid demonstrator prototype module containing the new calorimeter module electronics, but still compatible with TileCal legacy system was tested in ATLAS during 2019-2021. An upgraded ver-sion of the demonstrator with finalized HL-LHC elec-tronics is being assembled to be tested in testbeam campaigns at the Super Proton Syncrotron (SPS) at CERN. We present current status and results for the different tests done with the upgraded demonstrator system.