A handshake 100 metres underground isn’t something you see every day. But on Friday, 13 December, that’s exactly how Fabiola Gianotti, CERN Director-General, Frédérick Bordry, Director for Accelerators and Technology, Lucio Rossi, High-Luminosity LHC project leader, and Oliver Brüning, his deputy, marked the connection of the LHC tunnel with that of its successor, the High-Luminosity LHC. “This is a crucial milestone for the High-Luminosity LHC,” said Lucio Rossi. “These structures will house equipment that is needed to reach high luminosity.”

For the past 18 months, diggers have been at work underground to excavate the structures for the future accelerator. Work is focused on Point 1, where the ATLAS experiment is located, and Point 5, which houses the CMS experiment. Most of the equipment that will be installed in these locations is designed to boost the luminosity – or to put it another way, the number of collisions – at the heart of these two experiments. 

At each site, the underground constructions consist of a shaft around 80 metres deep, a service cavern, a 300-metre tunnel and four 50-metre tunnels connecting the new structures to the existing LHC tunnel. Around 80% of the excavations on the two sites are now complete: after having dug the shafts, the caverns and almost all of the two longer tunnels, the civil engineering companies are now working on the tunnels that will connect the new structures to the LHC tunnel. And as a result they connected the LHC with its successor, at Point 5 on 11 December and then at Point 1 the following day. “These connection works were completed with almost surgical precision, so as to minimise damage to the tunnel and to protect the LHC as much as possible from the dust produced by cutting through the concrete,” explains Pieter Mattelaer, Project Manager – Civil Engineering, High-Luminosity LHC Project.

A second connection between the new tunnels and the LHC tunnel should be completed before summer 2020. The underground structures will be fully completed by mid-2021, while the surface buildings will be completed by mid-2022.

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