The ATLAS experiment at CERN is constructing upgraded system
for the "High Luminosity LHC", with collisions due to start in
2029. In order to deliver an order of magnitude more data than
previous LHC runs, 14 TeV protons will collide with an instantaneous
luminosity of up to 7.5 x 10e34 cm^-2s^-1, resulting in much higher pileup and
data rates than the current experiment was designed to handle. While
this is essential to realise the physics programme, it presents a huge
challenge for the detector, trigger, data acquisition and computing.
The detector upgrades themselves also present new requirements and
opportunities for the trigger and data acquisition system.
The design of the TDAQ upgrade comprises: a hardware-based low-latency
real-time Trigger operating at 40 MHz, Data Acquisition which combines
custom readout with commodity hardware and networking to deal with
4.6 TB/s input, and an Event Filter running at 1 MHz which combines
offline-like algorithms on a large commodity compute service
with the potential to be augmented by commercial accelerators .
Commodity servers and networks are used as far as possible, with
custom ATCA boards, high speed links and powerful FPGAs deployed
in the low-latency parts of the system. Offline-style clustering and
jet-finding in FPGAs, and accelerated track reconstruction are
designed to combat pileup in the Trigger and Event Filter
This contribution will report recent progress on the design, technology and
construction of the system. The physics motivation and expected
performance will be shown for key physics processes.
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