About the High-Luminosity LHC

Read below to explore what the High-Luminosity LHC is, why it is important, and its technologies.

Video: CERN

The High-Luminosity LHC in a nutshell

The High-Luminosity Large Hadron Collider (AKA HiLumi LHC or sometimes written as HL-LHC) is the major upgrade to the current Large Hadron Collider (LHC), CERN’s flagship accelerator. It aims to crank up the performance of the LHC in order to increase its potential for discoveries after 2030, by increasing the luminosity – corresponding to a higher number of particle collisions, to generate more data for delving deeper into unanswered questions of particle physics.  

This extraordinary technical endeavour hinges on a number of innovative technologies, including cutting-edge superconducting magnets, crab cavities for beam rotation, and high-power superconducting links, as well as developments in collimation, powering, protection, cryogenics, vacuum, diagnostics, modelling and beam handling.

After five years of design studies and R&D ending in 2015, this challenging project is now nearing the end of ten years of development, prototyping, testing and series production. Installation and implementation of some technology and infrastructure is already well underway, and the major installation work in the LHC tunnel is due to take place during Long Shutdown 3, when the LHC will be switched off between July 2026 and mid-2030. 

You can read the CERN information pages about HiLumi LHC here.

What is luminosity, and what are the luminosity goals of HiLumi?

Luminosity is an important indicator of the performance of an accelerator: it is proportional to the number of collisions that occur in a given amount of time. The higher the luminosity, the more data the experiments can gather to allow them to observe rare processes. 

Instantaneous luminosity is the rate of potential collisions at a specific moment. 

Integrated luminosity is the total collected data size over a period of time, measured in inverse femtobarns (fb-1). One inverse femtobarn of integrated luminosity equates to 100 million million collisions.

The objective of HiLumi LHC is to achieve instantaneous luminosities of a factor of 5 to 7.5 larger than the LHC nominal value, thereby increasing the integrated luminosity by a factor of 10 beyond the LHC’s design value. This should enable the experiments to enlarge their data sample by one order of magnitude during the 12 years of HiLumi LHC operation compared with the LHC baseline programme. 

By the end of 2025, the LHC had produced 500 inverse femtobarns of data over its lifetime. The HiLumi LHC aims to produce more than 250 inverse femtobarns of data per year, capable of collecting up to 4000 inverse femtobarns during its operational period.

Why HiLumi LHC?

Witnessing rare phenomena not yet observable

The phenomena that physicists are looking for have a very low probability of occurring and this is why a very large amount of data is needed to detect them. Increasing luminosity produces more data, allowing physicists to study known mechanisms in greater detail and observe rare new phenomena which occur below the current LHC sensitivity level. 

For example, the HiLumi LHC could produce about 380 million Higgs bosons over its lifetime, compared with the roughly 55 million Higgs bosons that the LHC has produced since it began operating.

Getting the most out of the accelerator

In the coming years, many critical components of the accelerator will reach the end of their lifetime due to radiation damage and will thus need to be replaced. The upgrade phase is therefore crucial not only for the full exploitation of the LHC physics potential, but also to enable operation of the collider beyond the end of the nominal LHC exploitation in 2026.

What are the technologies behind HiLumi LHC?

Technically how this upgrade can be achieved is at the heart of the HiLumi LHC as upgrading such a large-scale, complex piece of machinery is a challenging endeavour which naturally takes time, effort and innovation. Details about each activity can be found on our Activities & Technologies pages.

This extraordinary technical challenge hinges on a number of innovative technologies, including cutting-edge niobium-titanium (Nb-Ti) and niobium-tin (Nb3Sn) superconducting magnets, compact and ultra-precise superconducting radio-frequency crab cavities for beam rotation, and 100-metre-long, high-power magnesium-diboride (MgB2) superconducting links with zero energy dissipation. The higher luminosities will also impose unprecedented demands on vacuum, cryogenics and machine protection, and requires new concepts for collimation such as bent crystals, advanced modelling for the intense beams and novel schemes of beam crossing to maximise the physics output of the collisions.

There are major associated upgrades to the ATLAS and CMS experiments for the high-luminosity era.

A detailed technical description of the project and its technological and operational challenges is provided in the HL-LHC Technical Design Report and the HL-LHC book.

Read more about all technologies
What is the schedule and status of the project?

This major upgrade is now in full swing of implementation together with its companion upgrade programmes: the LHC injectors upgrade (LIU) and detectors (ALICE, ATLAS, CMS, LHCb).

After five years of design studies and R&D ending in 2015, the HiLumi LHC Project is now nearing the end of ten years of development, prototyping, testing and series production. Installation and implementation of some technology and infrastructure is already well underway and teams are gearing up ahead of CERN’s next Long Shutdown, Long Shutdown 3 (LS3), when the machine will be switched off from July 2026 to mid-2030. HiLumi LHC is due to start up after this shutdown.

During LS3, deinstallation of many parts of the LHC will take place, followed by installation of new equipment for the HiLumi LHC accelerator, and the associated high-luminosity upgrades of the ATLAS and CMS experiments.

From the LHC to the HiLumi LHC

2008

First beam in the LHC

The first beam of protons was steered around the full 27-km LHC ring. The LHC, situated at the Franco-Swiss border near Geneva, is the largest instrument ever designed and built for scientific research. It has been exploring the high-energy frontier since 2010 and attracts a global user community of…
2009

LHC restarted

In November 2009, beams once again circled the LHC following repairs after a malfunction from September 2008.
2010

First physics in the LHC

The LHC restarted in February 2010 after a technical stop following its first full period of operation, which ended in December 2009. After 3.5 TeV proton beams successfully circulated on 19 March, the LHC produced the first high-energy proton-proton collisions at 7 TeV centre-of-mass energy on 30 …
2011

HiLumi LHC Design Study begins

Starting in November 2011, this preparatory project focused on designing technologies to make the HiLumi LHC’s goals possible. Initiated by CERN, this design phase was supported in part by funding from the Seventh Framework Programme (FP7) of the European Commission, involving European partners and …
2012

Discovery of the Higgs boson

On 4th July 2012 the LHC experiments, ATLAS and CMS, announced the first major discovery: the long-sought-after Higgs boson, the cornerstone of the Standard Model (SM) of particle physics. This announcement has been heralded by scientists, as well as by the media, as a giant leap in the understandin…
2012

LHC achieves 8 TeV collisions

In April 2012, the LHC produced proton-proton collisions at 8 TeV centre-of-mass energy, a factor of 4 greater than the previous record (held by Tevatron at the Fermi National Laboratory, USA).
2013

LHC Run 1 ends, LS1 begins

In February 2013, the first full run (Run 1) of the LHC ended. A two-year shutdown commenced, for a hive of maintenance activities to take place.
2015

HiLumi LHC as a priority project

As the pinnacle of 30 years of technological development, the LHC’s full exploitation was given the highest priority in the EU Strategy Report for High Energy Physics. Following this and the approval of its budget by CERN Council (Medium Term Plan 2015), the HiLumi LHC project embarked on a decade o…
2015

HiLumi LHC Design Study concludes

The design study formally concluded in October 2015. Drawing on worldwide expertise, it supported the technical feasibility of this highly complex and optimised machine, presenting a number of highly innovative technologies to achieve its goals. This marked a crucial stepping stone laying the founda…
2015

Start of Run 2 & 13 TeV collisions

After a two-year shutdown (LS1), beams started recirculating the LHC in April 2015. On 10 April, a new record was set with the LHC accelerating beams to 6.5 TeV. On 3 June, the LHC broke its own record, delivering physics data at 13 TeV.
2018

HiLumi LHC excavation works begin

In June 2018 a ground-breaking ceremony marked the start of excavation works at Points 1 and 5. This began the construction of new underground galleries sitting above the ATLAS and CMS experiments, to house key powering equipment for the HiLumi LHC. As these galleries are separate from the LHC, they…
2018

LHC Run 2 ends, LS2 begins

In December 2018, the second run of the LHC finished, and the second Long Shutdown (LS2) began. This 3-year shutdown saw key maintenance activities plus already some upgrades for the HiLumi LHC.
2019

HiLumi installations during LS2

During LS2 (2019-2022), upgrades for the HiLumi era were already taking place, including upgraded collimators at Point 7, new beam absorbers (TANB), and improved injection equipment (TDIS), as well as some upgrades to the detectors.
2022

HiLumi LHC galleries completed

The main civil engineering works at both Point 1 and 5 for HiLumi LHC were completed by the end of 2022. The new underground galleries and their corresponding service buildings were completed. The next 3-4 years would see the installation of entry points, lifts, and technical infrastructure.
2022

Start of Run 3, record 13.6 TeV

On 5 July 2022, the LHC was restarted for its third run, and later that day began recording physics collisions at a record of 13.6 TeV.
2026

End of Run 3

The last collisions of the LHC four large experiments were created on 11 June 2026, and the LHC was shut down on 29 June 2026.
2026

Start of LS3

After over a decade of research, development and production, the HiLumi LHC Project is in full swing, with completion of series production of many technologies and infrastructure for the galleries nearing completion. Long Shutdown 3 started on 29 June 2026, beginning the 4 years of transformation fr…