Design and Evaluation of the LAr Trigger Digitizer Board in the ATLAS Phase-I Upgrade

The Phase-I upgrade of the trigger readout electronics for the ATLAS liquid argon (LAr) calorimeters will be installed during the second long shutdown of the Large Hadron Collider (LHC) in 2019-2020, which will enable enhanced instantaneous luminosities during LHC Run 3 from 2021 through 2023. In this trigger upgrade, the so-called supercells are introduced to provide higher granularity, higher resolution, and longitudinal shower shape information from the LAr calorimeters to the Level-1 trigger processors. A new LAr trigger digitizer board (LTDB) will process and digitize up to 320 channels of supercell signals and transmit them via 40 fiber optical links to the back-end where the data are further processed and transmitted to the trigger processors. Five pairs of bidirectional GigaBit Transceiver links are used for slow control and monitoring between LTDB and the front-end link eXchange (FELIX) in the ATLAS trigger and data acquisition (TDAQ) system. The LTDB also outputs 64 summed analog legacy signals to the current tower builder board via a new baseplane. A test system for the production of 124 LTDBs has been developed, supporting configuration and calibration of all application-specified integrated circuits (ASICs) on the LTDB, as well as evaluation of full LTDB functionality.