The ATLAS experiment has undergone substantial improvements during Long Shutdown 2 (LS2). Thanks to luminosity levelling, a sustained running of the LHC at an instantaneous luminosity of L=2×10³⁴cm⁻²s⁻¹ is expected during LHC Run 3, with an average of up to 60 interactions per bunch crossing. To cope with such pileup conditions and to recover LHC Run 1 single-lepton trigger thresholds, the ATLAS detector has been upgraded in LS2. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels (NSW) with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC.
In the seminar the Run 3 configuration of the ATLAS detector will be presented with special emphasis on the improvements for the Liquid Argon Calorimeter and the Muon system

Coffee will be served at 10:30.