ATLAS Upgrade

ATLAS Upgrade
Name	ATLAS Upgrade
Caption	Upgrades to the ATLAS detector at the Large Hadron Collider
Location	CERN
Type	Particle detector upgrade project
Began	2013
Status	Ongoing

ATLAS Upgrade is the program of planned and implemented enhancements to the ATLAS detector at the Large Hadron Collider designed to cope with higher luminosity, increased radiation and pile-up, and to extend discovery potential for new physics beyond the Standard Model of particle physics. The effort interfaces with accelerator upgrades such as the High-Luminosity Large Hadron Collider and coordinates with detector experiments including CMS (particle detector), LHCb experiment, and ALICE. It involves institutions like CERN, national laboratories such as SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and universities across Europe, North America, and Asia.

Background and Motivation

The need for an upgrade grew from performance limits observed during runs at the Large Hadron Collider and the physics opportunities anticipated from the High-Luminosity Large Hadron Collider era. Increasing instantaneous luminosity at the LHC raises challenges including higher particle flux, radiation damage seen in sensors developed by collaborations like ATLAS Collaboration and CMS Collaboration, and event pile-up that affects analyses for processes studied at CERN. Motivations draw from discoveries and measurements such as the Higgs boson observation, precision tests linked to the Standard Model, and searches inspired by theories like Supersymmetry, Extra dimensions, and dark matter models explored in experiments such as XENON, LUX-ZEPLIN, and Fermi Gamma-ray Space Telescope studies.

Upgrade Phases and Timeline

The program is organized in phases aligned with accelerator shutdowns and milestones defined by CERN planning bodies. Phase-0 and Phase-I interventions correspond to earlier consolidation and improvements undertaken before the Run 2 and between runs, while Phase-II aligns with the High-Luminosity LHC deployment. Key milestones coordinate with schedules established by the European Strategy for Particle Physics and funding cycles involving agencies like European Research Council, United States Department of Energy, and Japan Society for the Promotion of Science. The timeline includes prototyping, production, installation during long shutdowns such as Long Shutdown 2 and Long Shutdown 3, and staged commissioning during beam periods.

Detector Subsystem Improvements

Upgrades span the inner tracker, calorimetry, muon spectrometer, and forward systems. The inner detector replacement with an all-silicon tracker draws on sensor technologies developed at institutes like CERN Microelectronics, University of Oxford, and Lawrence Berkeley National Laboratory; it improves vertexing critical for studies of top quark production, B meson decays studied also by LHCb, and exotic signatures. Calorimeter electronics upgrades preserve performance under radiation informed by tests at facilities such as DESY, CERN PS, and Fermilab Test Beam Facility. Muon system upgrades include new chambers influenced by developments at Saclay, INFN, and KEK, enhancing capabilities for searches similar to those pursued by experiments like ATLAS's peers. Forward proton tagging and timing detectors integrate precision timing technologies comparable to efforts in CMS and projects like TOTEM.

Trigger and Data Acquisition Enhancements

Trigger and data acquisition (TDAQ) systems are redesigned for higher trigger rates and bandwidths. The upgrade introduces a two-level hardware and software strategy parallel to systems used by CMS (particle detector), leveraging high-performance computing clusters like those in the Worldwide LHC Computing Grid and algorithms developed in collaborations with groups at CERN openlab, Intel Labs, and NVIDIA Research. Improvements incorporate real-time tracking in the trigger, firmware and FPGA advances from vendors used by ATLAS Collaboration partners, and dataflow architectures informed by experiments such as Belle II and IceCube Neutrino Observatory.

Performance Goals and Physics Impact

Performance targets include sustained tracking efficiency in high pile-up (hundreds of interactions per crossing), improved b-tagging and tau identification, enhanced mass resolution for resonances, and precise timing for vertex discrimination. Achieving these enables more sensitive searches for phenomena predicted by Supersymmetry, Composite Higgs models, Dark matter portals, and precision measurements of the Higgs boson couplings and rare processes like Higgs boson decays and top quark rare decays. Results feed into global fits by working groups such as those behind the Particle Data Group and influence theoretical programs involving researchers from institutions like Princeton University, MIT, University of Tokyo, and Instituto de Física Corpuscular.

Project Management and Costs

Management uses international governance frameworks similar to those at CERN experiments, with coordination among funding agencies including the European Commission and national ministries. Cost estimates account for detector fabrication, installation during long shutdowns, personnel, and computing infrastructure; they are benchmarked against large-scale projects like ITER and high-energy physics detector upgrades at SLAC. Risk mitigation follows models used by collaborations such as CMS Collaboration and project-management practices from laboratories like Brookhaven National Laboratory and Fermilab.

Test Beams, Commissioning, and Operations

Prototype components undergo characterization in test beams and irradiation campaigns at facilities including CERN PS, DESY, Fermilab Test Beam Facility, and TRIUMF. Commissioning phases integrate subsystems with beam operations coordinated with the CERN accelerator complex, following procedures developed during earlier commissioning of ATLAS and other LHC detectors. Ongoing operations require continuous calibration, alignment, and monitoring using software frameworks inspired by projects like Gaudi (software), and collaborative support from universities and national labs worldwide.

Category:Particle detectors