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 LHC at centre-of-mass energies up to 14 TeV and instantaneous luminosities up to $10^{34} \text{cm}^{-2} \text{s}^{-1}$. 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 $3000~\text{fb}^{-1}$. In the HL-LHC phase, the increased radiation levels require a replacement of the front-end electronics of the LAr Calorimeters. Furthermore, the ATLAS trigger system is foreseen to increase the trigger accept rate by a factor 10 to 1 MHz and the trigger latency by a factor of 20 which requires a larger data volume to be buffered. Therefore, the LAr Calorimeter read-out will be exchanged with a new front-end and a high bandwidth back-end system for receiving data from all 186.000 channels at 40 MHz LHC bunch-crossing frequency and for off-detector buffering. The talk will give an overview of the developement of radiation tolerant components like low-noise pre-amplifier and shapers, 10-14 bit and 40-80 MHz analog-to-digital converters (ADCs) with low power and latency, integrated serializer and optical transceivers, as well as a 140 Tb/s digital processing system based on high-performance FPGAs. Results from research and development of individual components and their radiation qualification as well as the overall system design will be presented.