Commissioning the Phase-1 LAr Upgrade

Liquid argon (LAr) sampling calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region ${|\eta| < 3.2}$, and for hadronic and forward calorimetry in the region from ${|\eta| = 1.5}$ to ${|\eta| = 4.9}$. In the first LHC run (Run-1), a total luminosity of 27~fb\textsuperscript{-1} was collected at centre-of-mass energies of 7-8~TeV. After detector consolidation during a long shutdown, Run-2 started in 2015 and around 150~fb\textsuperscript{-1} of data at a centre-of-mass energy of 13~TeV was recorded. With the end of Run-2 in 2018, a multi-year shutdown for the Phase-I detector upgrades began. As part of the Phase-I upgrade, new trigger readout electronics of the ATLAS Liquid-Argon Calorimeter have been developed. Installation began at the start of the LHC shut down in 2019 and is expected to be completed in 2020. A commissioning campaign is underway in order to realise the capabilities of the new, higher granularity and higher precision level-1 trigger hardware in Run-3 data taking. This contribution will give an overview of the new trigger readout system and the ongoing commissioning and installation efforts.