Future Circular Collider

The Future Circular Collider (FCC) study is developing designs for the next generation of higher performance particle colliders that could follow on from the Large Hadron Collider (LHC)

What?

The Future Circular Collider (FCC) study is developing designs for higher performance particle colliders that could follow on from the Large Hadron Collider (LHC) once it reaches the end of its (High-Luminosity phase).

The ongoing FCC Feasibility Study, expected to conclude in 2025, is investigating the technical and financial viability of the FCC at CERN, including geological feasibility, environmental impact, design of infrastructures, civil engineering and detectors, as well as R&D on technologies for the efficiency and sustainability of the proposed colliders.

A new tunnel is planned with a circumference of 90.7 km, an average depth of 200 m and eight surface sites for up to four experiments. The tunnel would initially house the FCC-ee, an electron–positron collider for precision measurements offering a 15-year research programme from the mid-2040s. A second machine, the FCC-hh, would then be installed in the same tunnel, reusing the existing infrastructure, similar to when the LHC replaced LEP. The FCC-hh aims to reach collision energies of 100 TeV, colliding protons and also heavy-ions, and running until the end of the 21st century. 

When?

The tentative timeline is:

  • 2025: Completion of the FCC Feasibility Study
  • 2027–2028: Decision by the CERN Member States and international partners
  • 2030s: Start of construction
  • Mid-2040s: FCC-ee begins operation and runs for approximately 15 years
  • 2070s: FCC-hh begins operation and runs for approximately 25 years 

For context, the physics case for the LHC was made in 1984; it then took about 10 years for the project to be approved and 25 years for the magnets to be developed and installed.

Why?

Physics case

The discovery of Higgs boson led to new questions, including “What role did the Higgs boson play during the Big Bang, and how did it influence the Universe’s evolution?” “Can the Higgs boson help explain other fundamental open questions that the Standard Model cannot address, including dark matter and the excess of matter over antimatter?”

Solutions to these questions can be found in the vast landscape of possible physics scenarios lying beyond the Standard Model. Some scenarios suggest the existence of new, heavier particles, beyond the reach of the LHC, calling for higher-energy facilities. Others suggest the existence of lighter particles that interact very weakly with Standard Model particles and whose detection requires huge amounts of data to be collected and great sensitivity to the elusive signals of their production. By providing considerable advances in sensitivity and precision with the FCC-ee and, ultimately, energy far beyond the LHC with the FCC-hh, the FCC programme would allow physicists to explore this new landscape in full.

CERN has several options for future colliders, which are either circular or linear in shape. The lightness of the Higgs boson and the no-show so far of other new elementary particles at the LHC make circular e+e- colliders an appealing alternative to linear machines. They enable significantly higher luminosity and up to four experiments, while also offering the infrastructure for a subsequent hadron collider.

Read more: FCC: The Physics Case in the CERN Courier.

FCC IN A NUTSHELL

Timeline

  • 2025: Completion of the FCC Feasibility Study
  • 2027–2028: Decision by CERN Member States and international partners

Tunnel

  • 90.7 km circumference
  • 200 m average depth
  • 8 surface points (7 in France, 1 in Switzerland)

Two stages

  • FCC-ee (precision measurements) about 15 years from the mid-2040s
  • FCC-hh (high energy) about 25 years from the 2070s

Costs/benefits

  • 15 billion CHF, spread over at least 15 years for FCC-ee with four experiments
  • Estimated benefit–cost ratio of 1.66
  • Local economic impact > €4 billion
  • About 800 000 person-years of employment created
Graphic of FCC
A schematic map showing a possible location for the Future Circular Collider (Image: CERN)

Return on investment

Beyond the creation of new knowledge, studies show that the FCC would deliver benefits that outweigh its cost. Impacts on industry from high-tech developments, the sustained training of early-career researchers and engineers, the development of open and free software, the creation of spin-off companies, cultural goods and other factors lead to an estimated benefit–cost ratio of 1.66. The FCC project is linked to the creation of around 800 000 person-years of employment, according to the FCC mid-term report, and the FCC-ee scientific programme is estimated to generate an overall local economic impact of more than €4 billion.

Read more: Machine Matters in the CERN Courier.

How?

Civil engineering

Sustainability is a major focus of the FCC civil-engineering studies, as FCC construction activities would result in about 16.4 million tonnes of excavated materials over a period of five years.

Comparative construction projects

Million tonnes of excavated material

FCC

16.4

Gotthard

28.2

Grand Paris

43

Lyon Turin

37

HS2 Phase 1

130

Crossrail

8

Stuttgart 21

40

 

To this end, the Mining the Future competition identified credible and innovative ways to reuse the molasse, including the use of limestone for concrete production and stabilisation of constructions within the project, the reuse of excavated materials to backfill quarries and mines, the transformation of sterile molasse into fertile soil for agriculture and forestry, the production of bricks from compressed molasse and the development of novel construction materials with molasse ingredients for use in the project where technically feasible.

The next step is to implement a pilot Open Sky Laboratory to demonstrate the separation techniques put forward by the winning consortium and collaborate with CERN’s Host States and other stakeholders to identify suitable locations for the use.

In addition, the FCC Feasibility Study is working to minimise the carbon footprint during construction and optimise transport systems between sites.    

Water

A thorough re-assessment revealed that the maximum water requirement during the operation of the FCC-ee at the top threshold (350 GeV) can be lowered to below 3 million m3 per year, which approximately corresponds to the present water use for the LHC.

Power

The FCC-ee would be the largest particle accelerator ever built, with its radio frequency cavities and magnet and cryogenic systems drawing the main power loads.

The FCC-ee power consumption is expected to vary between 1 and 1.8 TWh/year depending on the machine’s operation mode. Thanks to ongoing R&D efforts, the power consumption of the FCC-ee is expected to be 30–40% lower than it would be if it were built using current technologies. The FCC study team is also working with regional authorities to identify ways in which part of this energy may be reused for heating in local industries and public infrastructures.

Comparative power consumption

TWh/year

FCC-ee

Between 1 and 1.8

LHC

1.3

High-Luminosity LHC

1.6

Typical chemical production plant

6

French electricity production

510

Electrical power would be provided from the French electricity grid, and the system is designed so that no new sub-stations would need to be constructed for the different FCC-ee operation modes. Studies indicate that by the time the FCC comes into operation, a low carbon footprint can be achieved with an energy mix that contains a large fraction of energy from renewable sources. 

Cost

The cost of an FCC-ee with four interaction points is estimated to be CHF 15 billion, spread out over a period of at least 15 years, with around one-third being taken up by the tunnel.

Read more: Machine Matters and Tunnelling to the future in the CERN Courier.

Map of region showing potential placement of FCC tunnel
Eight surface points (P) are foreseen for technical infrastructure or scientific experiments, with seven in France and one in Switzerland: PA in Ferney Voltaire, PB in Présinge/Choulex (Switzerland), PD in Nangy, PF in Etaux, PG in Charvonnex/Groisy, PH in Cercier, PJ in Vulbens/Dingy and PL in Challex. (Image: CERN)

Where?

Following eight years of study, one configuration was identified out of some 100 variants as being particularly suitable. This scenario envisages a tunnel with a circumference of about 90.7 km, eight surface sites with underground facilities at depths of between 180 and 400 metres and up to four experiments.

Where possible, the study has considered non-exploited land, with site perimeters kept to a strict minimum and surface needs reduced by more than 60% compared to the initial plans. The FCC would reuse existing sites such as the 3 ha LHC surface site in Ferney-Voltaire (for FCC PA) and the Prévessin surface site (for the FCC injector accelerator).

Read more: Where and How in the CERN Courier.

Who?

The global FCC collaboration spans more than 150 institutes in more than 30 countries, while new partners are still being sought to work on research and development.

Read more: The People Factor in the CERN Courier.