The ATLAS Readout System for LHC Runs 2 and 3

TL;DR

This paper details the design, implementation, and performance of the upgraded ATLAS ReadOut System for LHC Runs 2 and 3, highlighting its hardware, performance metrics, and re-use in other components.

Contribution

It presents the complete redesign and deployment of the ATLAS ROS for LHC Runs 2 and 3, including performance evaluation and technology reuse.

Findings

System met the demanding data throughput requirements.

Performance measurements confirmed system reliability and efficiency.

Reused ROS technology for other ATLAS data acquisition components.

Abstract

The ReadOut System (ROS) is a central part of the data acquisition (DAQ) system of the ATLAS Experiment at the CERN Large Hadron Collider (LHC). The system is responsible for receiving and buffering event data from all detector subsystems and serving these to the High Level Trigger (HLT) system via a 10 GbE network, discarding or transporting data onward once the trigger has completed its selection process. The ATLAS ROS was completely replaced during the 2013-2014 experimental shutdown in order to meet the demanding conditions expected during LHC Run 2 and Run 3 (2015-2025). The ROS consists of roughly one hundred Linux-based 2U-high rack-mounted servers equipped with PCIe I/O cards and 10 GbE interfaces. This paper documents the system requirements for LHC Runs 2 and 3 and the design choices taken to meet them. The results of performance measurements and the re-use of ROS technology for the development of data sources, test platforms for other systems, and another ATLAS DAQ system component, namely the Region of Interest Builder (RoIB), are also discussed. Finally performance results for Run 2 operations are presented before looking at the upgrade for Run 3.