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 focusing magnets and new advanced technologies in the domain of superconductivity, cryogenics, rad-hard materials, electronics and remote handling. Civil-engineering works will have to be carried out to create space to host part of the technical infrastructures required by this new equipment. Construction of the HL-LHC should be completed in 2026 and will be followed by at least ten years of operation.

  • 2018–2022: Major Civil Engineering works.
  • 2018–2024: Construction and test of hardware components.
  • 2019−2020: Installation during LS2 of the DS collimators, with 11 T dipole in P7, low-impedance collimators, new beam instrumentation and injection system protection.
  • 2021–2025: Preparation of infrastructure in the tunnel and new service galleries.
  • 2022–2023: String test of inner triplet.
  • 2024–2026: LS3 – Installation and commissioning of main hardware: Inner Triplet Quadrupoles, Crab cavities, SC links, new large Cryo-plants and all other equipment.

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), Point 7 (Ornex) and Point 8 (Ferney-Voltaire) is exclusively underground and involves the replacement of existing equipment in the LHC. This work will take place mainly during Long Shutdown 2 (2019 – 2020).

The work at Point 4 (Echenevex) involves infrastructure both above and below ground: it will also take place during Long Shutdown 2cand essentially 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.

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

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

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