The HL-LHC ATLAS (trigger) upgrade

The LHC is currently planned to operate for a total of three running periods (Run 1 - Run 3), up to the year 2024. It will then be upgraded to provide the experiments with data rates larger than ever before, resulting, over ten years, in a data set about ten times larger than what the LHC will have provided in its lifetime. The impact to particle physics will be enormous: the reach of the searches for new physics will be extended substancially and the study of the properties of the Higgs Boson will proceed to the most difficult and rare channels. The so-called "High-Luminosity LHC" (HL-LHC) will be installed during a long shutdown, currently envisaged for 2025-2027. For the prospected event rates to be achieved, the average number of collisions per bunch crossing ("pile-up") will be increased to unprecedented quantities (up to 200, from a maximum of 60 in Run 2). To handle the huge rates of incoming data, as well as radiation, the LHC upgrade will be naturally complemented by upgrades of the experiments.

The ATLAS experiment is planning on replacing entirely the inner detector tracking volumes to cope with the high occupancy. The new tracker will be an all-silicon tracker of high granularity and providing larger coverage towards the forward regions with respect to the current tracker. The calorimeter and muon detectors will be upgraded to ensure efficient data taking despite the high number of collisions per bunch crossing. And finally, a new trigger and data acquisition (TDAQ) system will be implemented not only to maintain the event selections but also to improve triggering capabilities to levels similar to those of Run 1.


The upgraded ATLAS TDAQ system will be feeding full-granularity detector data into a first, hardware-based trigger level, which will be providing 1 MHz selection rate, and a second event filter, combining software selections with tracks reconstructed in (custom-made or commodity-based) hardware. Following RnD and demonstrators for a custom-made hadrware system, the ATLAS experiment is now optimising the design towards prototyping. It is planned that 10 kHz of physics data are written out for further processing and analysis during the HL-LHC phase.



More on ATLAS (and CMS) upgrades on tracking and data aquisition in this conference talk.
More on the ATLAS trigger system in this seminar talk.