The Phase-I trigger readout electronics upgrade of the ATLAS Liquid Argon calorimeters

Abstract

The Phase-I trigger readout electronics upgrade of the ATLAS Liquid Argon calorimeters enhances the physics reach of the experiment during the upcoming operation at increasing Large Hadron Collider luminosities. The new system, installed during the second Large Hadron Collider Long Shutdown, increases the trigger readout granularity by up to a factor of ten as well as its precision and range. Consequently, the background rejection at trigger level is improved through enhanced filtering algorithms utilizing the additional information for topological discrimination of electromagnetic and hadronic shower shapes. This paper presents the final designs of the new electronic elements, their custom electronic devices, the procedures used to validate their proper functioning, and the performance achieved during the commissioning of this system.

ATLAS toward the High Luminosity era: Challenges on electronic systems

“…Particularly challenging is the pile-up (the number of average interactions per bunch crossing), expected to be of the order of 200 (about five times higher than today). Some upgrades (Phase-I upgrades) have already been carried on for current data taking (Run 3): the installation of a new LAr digital trigger electronics [2], the L1calo trigger and the installation of the New Small Wheel (sTGC + Micromegas) and sMDT (small diameter MDT) plus small-gap RPC in some regions (BIS78) of the Muon System. The Phase-II upgrades will include a completely new inner tracker (ITk), endcap timing layers (HGTD) and the installation of additional muon chambers.…”

ATLAS LAr Calorimeter Commissioning for LHC Run-3

“…Figure 5: Measured E T per ADC count as function of η position of the SCs at ϕ = 1.62 (ϕ = 1.66) and 0 < η < 2.5 (2.5 < η < 3.2), corresponding to a ∆ϕ granularity of 0.1 (0.2) for different calorimeter layers [5].…”

Quality Assurance and Testing of the Atlas Liquid Argon Calorimeter Power Distribution Boards

“…From the two +6 V lines available on the input power bus, one (labelled "6 V") is used to generate the digital voltages and the other one "6 VA" is used to generate the analog voltages. Picture from [3] From the +6 V line taken from the Front-End Crate (FEC) power bus, the following voltages are created for the digital part of the LTDB: +1.2V, +1.5V, +2.5V and +3.3V. This is achieved using LTM4619 DC-DC converters.…”

“…In particular, for the liquid argon calorimeter, to avoid efficiency losses and enhance the physics reach, it was decided to increase the trigger readout granularity by up to a factor of ten, summing the the transverse energy (ET) of calorimeter cells in areas smaller than the previous configuration (these smaller clusters of cells are called Super Cells). In addition, the precision and range of the ET measurement is also increased [3]. The Lar Trigger Digitizer Board (LTDB) processes and digitizes up to 320 Super Cell signals and transmits them via optical links to the Back-End.…”