The High-Luminosity LHC (HL-LHC)

What is the High-Luminosity LHC project?

CERN’s Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator. It has operated successfully since 2008 and at very high energy (13 TeV) since 2015. The data collected allowed the ATLAS and CMS experiments to discover the Higgs boson after decades of research.

The High-Luminosity Large Hadron Collider (HL-LHC) is an upgraded version of the LHC: it will operate at a higher luminosity, or in other words it will be able to produce more data. The HL-LHC will enter service after 2025, increasing the volume of data analysed by the ATLAS and CMS experiments by a factor of 10.

The full exploitation of the LHC, including its upgraded version, the HL-LHC, was defined as the top priority for particle physics in Europe in the 2013 update of the European Strategy for Particle Physics.

What sort of research will be carried out at the HL-LHC?

Exploration of the energy scale made accessible by the LHC (several TeV) has only just begun. Decades of additional data from the LHC will be necessary to complete the process. This research is essential, as the results will change our perception of the fundamental laws of nature. In particular, it will allow us to continue our measurements of the particles predicted by the Standard Model, the theoretical model of particles and forces, and to identify any discrepancies between the experimental results and the theory. It will also allow us to verify if other particles exist at the LHC energy scale. Their existence might resolve some of the outstanding puzzles of contemporary physics, such as the presence of the enigmatic dark matter.

What is the timeline for the project?

Although most of the existing components of the LHC will remain in place, operation at higher luminosity requires new components to be developed, such as more powerful magnets, and civil-engineering work to be carried out. Construction of the HL-LHC should be completed in 2026 and will be followed by at least ten years of operation.


  • 2016 – 2017: Tests of prototypes of the main components
  • 2018 – 2021: Civil-engineering work at Points 1 and 5 of the LHC
  • 2018 – 2023: Construction and testing of all the new components
  • 2019 – 2020: Installation of the first components during the second Long Shutdown of the LHC
  • 2020 – 2023: Work on the technical infrastructure at Points 1 and 5 of the LHC
  • 2020 – 2022: Integration tests of the components in the interaction region
  • 2024 – 2026: Installation and commissioning of the components during the third Long Shutdown of the LHC

Where will the work take place?

The diagram below shows the location of the work required for the HL-LHC project.


The work at Point 2 (Sergy), Point 6 (Versonnex) and Point 8 (Ferney-Voltaire) is exclusively underground and involves the replacement of existing equipment in the LHC. This work will take place during Long Shutdown 2 (2019 – 2020).

The work at Point 4 (Echenevex) involves infrastructure both above and below ground: it will also take place in 2019-20 and esentially consists of modifications to the cryogenic system..

More significant work will be carried out at Points 1 (Meyrin) and 5 (Cessy), which house the two general-purpose experiments, ATLAS and CMS. Civil-engineering work will be required at these locations to create the space required for the new technical installations needed to increase the luminosity of the LHC.

This work will be carried out in three phases:

  • 2018 – 2021: Civil engineering
  • 2020 – 2023 : Technîcal Infrastructure
  • 2024 – 2025 : Completion of civil engineering and installation of components

New underground installations (in blue) at Point 1 (Meyrin)

New underground installations (in blue) at Point 5 (Cessy)

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