Future Circular Collider conceptual design report submitted

22 January 2019

Switzerland – Scientists and engineers at CERN have submitted the concept design report for the Future Circular Collider (FCC). This is a 100km-circumference particle-smashing machine that dwarfs the existing 30km Large Hadron Collider (LHC), and of course it will also need to be tunnelled.

One of the glories of modern science is the ‘Standard Model’ of particle physics. Despite their best efforts, scientists have consistently failed to find anything wrong with it, and as the long-predicted particles are discovered one at a time, their properties can be ‘plugged in’ to various formulae and other models to refine our understanding of the universe. Readers may be aware of the recent discovery of the Higgs Boson which is generally thought to complete the standard model. This was thanks to the existing LHC, and the tunnelling industry.

The proposed structure (see feature, Tunnels and Tunnelling International, June 2016 for a more detailed look at earlier plans) will have an energy rating of 100TeV (tera electron volts) against the LHC’s 14TeV and will allow scientists to move beyond the science of the 20th century, and there is a whole range of experimental and observational oddities that are not yet fully understood [readers are encouraged to Google ‘unsolved problems of physics’ – Ed].

A spokesperson for CERN said, “The cost of a large circular electron-positron collider would be in the 9-billion-euro range, including EUR 5bn for the civil engineering work for a 100km tunnel. This collider would serve the worldwide physics community for 15 to 20 years. The physics programme could start by 2040 at the end of the High-Luminosity LHC. The cost estimate for a superconducting proton machine that would afterwards use the same tunnel is around EUR 15bn. This machine could start operation in the late 2050s.”

One of the defining parameters of the new tunnel is that it must be able to connect with the Large Hadron Collider which will act as a pre-accelerator for the beams.

"We have tried to maximise the amount of FCC in the molasse and minimise the amount in the limestone because in this region the limestone is heavily karsified and the fractures filled with muddy watery materials which caused a lot of problems when they were building the LEP tunnel," CERN civil engineer Charlie Cook told Tunnels and Tunnelling in 2016.

But given the size of the tunnel and the topography of the region with its mountainous terrain some limestone excavation seems inevitable. CERN is surrounded with the Jura Mountains to the west, the pre Alps on the east and south east, and the Saleve in the middle of the FCC, south east of CERN.

These projects are also categorised by enormous shafts; the precision nature of the equipment often meaning that it has to be of monolithic design. Shafts hundreds of metres deep and up to 30m in diameter have previously been discussed.

The FCC study started in 2014 and stems directly from the previous update of the European Strategy, approved in May 2013, which recommended that design and feasibility studies be conducted in order for Europe “to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next Strategy update”. And over the next two years, the particle physics community will be updating the European Strategy for Particle Physics, outlining the future of the discipline beyond the horizon of the Large Hadron Collider (LHC).

Ring overlayed on the Geneva Basin
Replacement of LHC dipole magnets during 'long shutdown 1', showing the need for large-diameter access shafts
Existing LHC tunnel interior
Artist's concept of the future tunnel interior