In coming years the LHC is expected to undergo upgrades to increase both
the energy of proton-proton collisions and the instantaneous luminosity.
In order to cope with these more challenging LHC conditions, upgrades of
the ATLAS trigger system will be required. This talk will focus on some
of the key aspects of these upgrades. Firstly, the upgrade period
between 2019-2021 will see an increase in instantaneous luminosity to
$3\times10^{34} \rm{cm^{-2}s^{-1}}$. Upgrades to the Level 1 trigger
system during this time will include improvements for both the muon and
calorimeter triggers. These include the upgrade of the first-level
Endcap Muon trigger, the calorimeter trigger electronics and the
addition of new calorimeter feature extractor hardware, such as the
Global Feature Extractor (gFEX). An overview will be given on the design
and development status of the aforementioned systems, along with the latest
testing and validation results.
By 2026, the High Luminosity LHC will be able to deliver 14 TeV
collisions with an order of magnitude larger instantaneous luminosity,
expected to reach $7.5 \times 10^{34} \rm{cm^{-2}s^{-1}}$.
ATLAS is planning a series of upgrades to prepare for this even more
challenging environment. This paper will describe the baseline
architecture for this upgrade, while also detailing on-going studies
into new system components and their interconnections. The overall
challenge here is to meet low latency and high data throughput
requirements within the limits given by technological evolution. A
discussion on the physics motivations and the expected performance based
on simulation studies will be presented, together with the open issues
and plans.