Broadening tunnel vision for future accelerators

CERN’s civil engineers are tackling the tunnelling challenges of a post-LHC collider

HL-LHC Underground civil engineering galleries progress
Tunnels and underground galleries are currently being excavated to prepare for an upgrade of the Large Hadron Collider (Image: Julien Ordan/CERN)

What could the next generation of particle accelerators look like? With current technology, the bigger an accelerator, the higher the energy of the collisions it produces and the greater the likelihood of discovering new physics phenomena. Particle physicists and accelerator engineers therefore dream of machines that are even bigger than the Large Hadron Collider (LHC), with its 27-km circumference.

For CERN’s civil engineers, a new accelerator requires a bespoke deep-underground tunnel, and the tunnel’s shape, depth and orientation as well as its access shafts are largely constrained by the local geography. Such an accelerator built at CERN would be bound by mountains, and, if circular, would need to go under Lake Geneva and completely enclose the Salève mountain of the Prealps.,Civil Engineering and Infrastructure
Two proposed post-LHC accelerators – CLIC and the FCC – present unique challenges to CERN’s civil engineers (Image: CERN)

The two largest projects under consideration for a post-LHC collider at CERN are the Compact Linear Collider (CLIC) and the Future Circular Collider (FCC). Their scale would dwarf CERN’s existing infrastructure, making them some of the largest tunnelling projects in the world. Civil engineers therefore need to survey the geological, environmental and technical constraints of these machines.

A tunnelling workshop that took place last week at CERN brought together civil-engineering experts from industry and academia to examine how new technologies and methods could optimise tunnel design and asset management. It is part of ongoing collaborations that have already seen CERN and the engineering consultancy Arup develop a first-of-its-kind tunnel optimisation tool to provide the best design when fed all the required parameters. The tool has already shown the feasibility of tunnels for either the FCC or CLIC in the local area, to help support the ongoing update for the European Strategy of Particle Physics that will guide the direction of particle physics and related fields to the mid-2020s and beyond.

Find out more about the tunnelling challenges of CERN’s civil engineers for the next-generation of particle accelerators in “Tunnelling for Physics” on the CERN Courier’s website.