Research and Development for a Free-Running Readout System for the ATLAS LAr Calorimeters at the High Luminosity LHC

The ATLAS Liquid Argon (LAr) Calorimeters were designed and built to measure electromagnetic and hadronic energy in proton-proton collisions produced at the Large Hadron Collider (LHC) at centre-of-mass energies up to \SI{14}{\tera\electronvolt} and instantaneous luminosities up to \SI{d34}{\per\centi\meter\squared\per\second}. The High Luminosity LHC (HL-LHC) programme is now developed for up to 5-7 times the design luminosity, with the goal of accumulating an integrated luminosity of \SI{3000}{\per\femto\barn}. In the HL-LHC phase, the increased radiation levels require a replacement of the front-end (FE) electronics of the LAr Calorimeters. Furthermore, the ATLAS trigger system is foreseen to increase the trigger accept rate and the trigger latency which requires a larger data volume to be buffered. Therefore, the LAr Calorimeter read-out will be exchanged with a new FE and a high bandwidth back-end (BE) system for receiving data from all \num{183000} channels at \SI{40}{\mega\hertz} LHC bunch-crossing frequency and for off-detector buffering. The article will give an overview of the developement of radiation tolerant components. Results from research and development of individual components and their radiation qualification as well as the overall system design will be presented.