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High-Luminosity ATLAS

Upgrading the experiment for the HL-LHC Era (2030–2041)

After years of foundational discoveries, the ATLAS Experiment is preparing for its most ambitious phase yet: the High-Luminosity Large Hadron Collider (HL-LHC or HiLumi LHC) upgrade. Scheduled to run from 2030 to 2041, the HL-LHC will dramatically increase the collider's intensity, or “luminosity”. Up to 200 proton-proton collisions are expected every time the proton beams cross, providing immense statistical power to explore the structure of matter and its fundamental interactions.

The ATLAS Experiment will be transformed with next-generation detector technologies in order to record data in this dense collision environment. Across ATLAS institutes around the world, researchers have spent years designing, constructing and testing the next generation of detector technologies that are being installed at CERN during the long shutdown period prior to 2030. Highlights of the upgrade activities can be found below.

General HL-LHC resources:

HL-ATLAS
Overview of upgrade projects underway at the ATLAS experiment during the LS3 (Long Shutdown 3) upgrade period. (Image: ATLAS Collaboration/CERN)

The New All-Silicon Inner Tracker (ITk)

Sitting at the heart of the upgraded ATLAS experiment will be the new Inner Tracker (ITk) — a massive, all-silicon tracking system, spanning 6 metres in length and 2 metres in diameter, designed to map the trajectories of charged particles with micrometre precision.

The tracker is split into two specialized systems to handle different tracking requirements: the ITk Pixel detector, operating just 33 mm from the HL-LHC beam, and the ITk Strip detector, which surrounds the Pixel detector. This combination of dense, high-resolution pixel tracking and extended strip coverage provides the massive increase in granularity needed to isolate individual particle paths out of the dense HL-LHC collision environment.

Key Numbers

  • 13 square metres of silicon pixel detector with over 5 billion readout channels
  • 165 square metres of silicon strip detector with 60 million readout channel

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ATLAS,ITk,tracker,Detectors
Staves are the building blocks of the ATLAS Inner Tracker (ITk) Strip Barrel. Here, members of the ITk team conduct a test insertion of a stave into the detector's barrel at CERN. (Image: P. Traczyk/CERN)

High-Granularity Timing Detector

The new High-Granularity Timing Detector (HGTD) adds a crucial fourth dimension to particle tracking: time.

When hundreds of collisions occur at once, particle tracks can overlap and appear to come from the same point. By measuring the arrival time of charged particles with picosecond precision, the HGTD separates tracks using tiny differences in timing, suppressing pile-up and helping identify particles from the collision of interest.

HGTD
Low-Gain Avalanche Detector (LGAD) sensors for the ATLAS High-Granularity Timing Detector. (Image: K. Wu/ATLAS Collaboration)

The HGTD consists of two 2-metre-diameter disks mounted on either side of the new ITk. It uses ultra-thin Low-Gain Avalanche Diode (LGAD) silicon sensors to deliver the timing precision needed to distinguish particles separated by just a few tens of trillionths of a second.

Key numbers

  • 50 µm thin silicon sensors
  • 3.6 million readout channels
  • 6.4 m² of silicon sensors
  • 30 to 50 picoseconds of timing resolution per track

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Next-Generation Trigger and Data Acquisition

With the HL-LHC pushing collision rates to unprecedented levels, the ATLAS Trigger and Data Acquisition (TDAQ) system is evolving to keep pace through next-generation electronics and cutting-edge computing architectures.

A new hardware-based trigger relies on modern, large-scale Field Programmable Gate Arrays (FPGAs) to run advanced filtering algorithms in real time. This system will perform the initial event selection, preserving events that are interesting for study while reducing the data rate. The new system will have access to the full calorimeter and precise muon measurements, allowing for sophisticated event reconstruction at the hardware trigger level for the first time. The software-based High-Level Trigger (HLT) is also being restructured to utilise GPUs, allowing it to efficiently process computationally heavy tasks like real-time particle tracking.

Key numbers

  • 1 MHz first-level hardware trigger rate, 10 times higher than LHC era
  • 10 kHz of refined data passed to storage
  • 3 to 5 times more data volume than previous runs

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Member of the ATLAS trigger group (Silvia Franchino) in front of the trigger racks located in a service hall adjacent to the ATLAS experiment cavern. (Image: N. Caraban Gonzalez/CERN)

Upgrading Legacy Detectors

Many of the legacy detectors of the ATLAS experiment will continue to play a vital role in the High-Luminosity LHC era through extensive upgrades with new detector systems, state-of-the-art electronics, and enhanced radiation tolerance.

smdt
Assembly of a new small Muon Drift Tube (sMDT) to be added to the ATLAS Experiment's Muon Spectrometer.

New resistive plate chambers (RPC) in the inner layer of the barrel muon spectrometer, partly accompanied by new small-diameter monitored drift tubes, will improve the fast online muon acceptance. Further, new on-detector and off-detector electronics will be added to the calorimeters and muon systems to accommodate the higher trigger rates and enhance overall performance. These upgrades will also improve the radiation hardness of the experiment.

Precise knowledge of the luminosity is key for the ATLAS physics programme. ATLAS will also upgrade the LUCID (Luminosity Cherenkov Integrating Detector) detector, a luminometer that is sensitive to charged particles produced at the interaction point, and install a new Pixel Luminosity Ring detector and a new 3D diamond-based Beam Conditions Monitor in the ITk. In the forward region, the Zero-Degree Calorimeter, which is particularly important for determining the centrality in heavy-ion collisions, is also being redesigned for HL-LHC running.

Key numbers

  • 40 MHz high-precision readout from new calorimeter electronics
  • 15 mm diameter monitored drift tubes

Learn more

More Upgrade Multimedia

Testing,Milestones,Technology,Detectors,ATLAS
Alignment check in the Inner Tracker (ITk) barrel prior to the practice insertion of an ITk Strips stave. (Image: A. Barr/ATLAS Collaboration)
ATLAS
Testing of the HGTD demonstrator at CERN. (Image: S Guindon and Z. Ge/ATLAS Collaboration)
Removal of beam vacuum assembly from ATLAS, which includes the LUCID detector.
ITk team
ATLAS members pose next to the Pixel Support Tube at Berkeley Lab. (Image: The Regents of the University of California, Lawrence Berkeley National Laboratory)

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Long Shutdown 2

Muon Spectrometer

Magnet System

Trigger and Data Acquisition

Software and Computing

Technology Transfer

Natural Units

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Natural Units

Our universe is governed by a handful of fundamental constants, such as the speed of light or the gravitational constant. In particle physics, it is often convenient to use natural units, in which key constants are set to unity, revealing the underlying simplicity of physical laws.

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Spin & Polarisation

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Spin and Polarisation

Spin is a fundamental property of particles, corresponding to their intrinsic angular momentum. Polarisation describes how the spin of a particle is oriented.

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2025 Thesis Award Winners

ATLAS Year
2025

The ATLAS Thesis Award winners for 2025 are:

See the News Article on the 2025 Awards.

ATLAS Open Virtual Visit

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Join us for an Open ATLAS Virtual Visit, hosted by ATLAS physicists Christian Appelt and Despoina Sampsonidou.

This live virtual event will take you inside the ATLAS cavern at CERN, offering a rare opportunity to see the ATLAS detector up close before the cavern is closed for LHC operation. From 100 meters underground, the hosts will guide you around one of the world’s largest and most sophisticated scientific instruments.

Pile-Up

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Pile-Up

The LHC collides bunches (groups of protons), which can result in multiple proton-proton collisions at each crossing. Such additional collisions are called pile-up.

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ATLAS Coordinate System

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ATLAS Coordinate System

The ATLAS coordinate system allows scientists to accurately and consistently describe how particles travel through the detector.

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Inside a Collision

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Inside a Collision

Proton collisions at the LHC generate high-energy events, initiating a cascade of processes, such as parton showering and hadronisation, which ultimately produce the particles seen in the ATLAS detector.

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2025 Outstanding Achievement Award Winners

ATLAS Year
2025
ATLAS Award
ATLAS Outstanding Achievement Award

The ATLAS Outstanding Achievement Award winners for 2025 are:

  • Masato Aoki (KEK), Leesa Brown (Victoria and TRIUMF), George Chatzianastasiou (CERN and BNL), Thiago Costa de Paiva (University of Massachusetts Amherst)(not pictured), Nathan Felt (Harvard)(not pictured), Simone Francescato (Harvard), Eleni Kanellaki (Demokritos)(not pictured), Foteini Kolitsi (uniWA), Audrey Kvam (University of Massachusetts Amherst), Callum McCracken (Vancouver UBC and TRIUMF), Tomoyuki Saito (Tokyo ICEPP), Yoshiaki Tsujikawa (Kyoto) for the deployment of the complete Phase-I L1 Muon Endcap Trigger, including the NSW triggers, enabling ATLAS to run at higher pileup and gather more data in 2024.
  • Doug Benjamin (Brookhaven BNL)(not pictured), Andrej Filipcic (Jozef Stefan Institute, Ljubljana)(not pictured), Michal Svatos (Prague AS), Rod Walker (Munich LMU)(not pictured) for advancing the experiment’s computing infrastructure through the integration of HPCs, which contribute substantially to ATLAS’s Run 3 computing power.
  • Brian Andrew Cole (Columbia), Riccardo Longo (Urbana UI) for contributing to the installation, commissioning and operation of the ZDC detector and responding to multiple challenges in November 2024.
  • Bojan Hiti (Jozef Stefan Institute, Ljubljana)(not pictured), Alissa Howard (Jozef Stefan Institute, Ljubljana)(not pictured), Xuewei Jia (Beijing IHEP), Mengzhao Li (Beijing IHEP)(not pictured), Chihao Li (CERN), Kuo Ma (USTC)(not pictured), Theodoros Manoussos (CERN), Weiyi Sun (IHEP CAS), Guilherme Tomio Saito (Universidade de São Paulo), Iskra Velkovska (Jozef Stefan Institute, Ljubljana), Xiao Yang (USTC)(not pictured), Mei Zhao (Beijing IHEP)(not pictured) for the successful design and testing campaign of the HGTD LGAD sensors that led to the start of sensor production.
  • Tobias Bisanz (Dortmund) for management of pixel code and databases, improving reliability and speed of detector calibrations, contributions to operations, and substantial improvements to system stability and monitoring in 2024.
  • André Rummler (CERN) for years of exceptional management of ATLAS operations, including significant interventions in 2024 to manage the recovery of the ATLAS infrastructure in the face of cooling challenges, enabling excellent data-taking efficiency.
  • Huacheng Cai (Pittsburgh), Etienne Fortin (CERN)(not pictured), Davide Mungo (Toronto), Pavol Strizenec (Kosice)(not pictured) for successful operation of the LAr detector, including contributions to online software and detector control systems, while commissioning the digital trigger.

See the News Article on the 2025 Awards

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