Title: "The ATLAS Trigger - Run 2 and the upgrade challenges towards the High Luminosity LHC"

Abstract: The ATLAS Trigger system has been operating very successfully during the LHC Run 2, between 2015 and 2018, reaching its ultimate performance this year. The trigger selection capabilities of ATLAS during Run 2 have been significantly improved compared to Run 1, in order to cope with the higher event rates and with the large number of simultaneous proton-proton interactions (pile-up).  By the beginning of 2018 more than 1500 different trigger selections had been compiled into a "trigger menu", covering all aspects of the ATLAS physics program and following the rise in LHC luminosity.

For the next two years the focus will be on the preparations for the LHC Run 3, which will commence in 2021. This upgrade though is only a stepping stone towards the High Luminosity (HL-)LHC, planned to start in 2024, which will bring an unprecedented luminosity of 5.0-7.5x10e34cm-2s-1.

The presentation will give an overview of the ATLAS trigger system in Run-2, before describing the challenges for the ATLAS Trigger System to prepare for the HL-LHC.