08 DECEMBER 2025 | Kristiane Bernhard-Novotny
Today marks the beginning of the Year-End Technical Stop 2025–26 (YETS), a period in which CERN’s North Area shifts from high-intensity operation to an equally intense phase of maintenance and renewal. During the YETS, the North Area fills with activity: the only moment in the year when deep technical work, inspections and safety upgrades can be carried out without the constraints imposed by beam operation. Under the North Area Consolidation programme NA-CONS, specialists from across CERN now begin a carefully sequenced set of interventions designed to make the North Area safer, more reliable and better prepared for Run 2026 and the years that follow.
A major part of this winter’s work centres on safety, with the installation of the first fours fire-resistant partitions. These structures mark the beginning of the compartmentalisation of the North Area, creating safer zones, shorter evacuation paths and barriers that prevent smoke from travelling through tunnels, galleries and the tall shafts that connect the underground to the surface. Their purpose is simple: to give people time and space to evacuate, and to give firefighters a more controlled environment in which to intervene if it ever becomes necessary. The new fire doors, aspirating detection pipes and alarm speakers being installed across the complex complement this effort. Throughout the winter, tests and commissioning will verify that the new systems behave as intended, forming the backbone of a modernised safety architecture.
In TCC2, the heart of the North Area where the beam from the SPS hits the production targets to fuel the North Area’s secondary beamlines serving many test-beam users and experiments, work advances on a slow-extraction test bench, where the new BDF prototype target will be integrated on a plug-in table for the future SHiP experiment. The upgrade includes the replacement of the upstream beam monitor, the removal of the current water-cooling skid and the installation of a new pressurised-helium skid. Additional pipework, electronic racks and a temporary heat exchanger will be installed, and modifications to the TCC2 door will allow correct routing. These interventions are essential steps for the next phase of the BDF programme and can only be performed during a full shutdown. Another important strand of the YETS works is the rack parallelisation in BA80, which prepares the building for the consolidation phase planned for LS3. A new Starpoint will be created during this winter stop, replacing an older system and giving the building a more resilient digital and electrical backbone. This includes installing a new equipment rack, upgrading the power connections so critical systems can continue running even during electrical interruptions, and laying new fibre links to CERN’s computing network. Two network switches will complete the setup: one for standard IT services and one dedicated to machine protection, controls and safety.
Electrical consolidation continues in EHN1. The hall’s secured network, once based on a radial layout, is being transformed into a closed-loop system supplied from the BE91 generator station, improving redundancy and stability. During design reviews, the need for additional capacity became clear, leading to the installation of a new transformer and a new switchboard. These additions ensure that EHN1 can meet future power demands without compromising operational resilience. The winter is also being used to enrich the way the North Area is documented. High-resolution panoramic images of the beamline magnets are being taken to give experts remote access to detailed visual information during operation, when entering the zones is impossible. These images are equally valuable for outreach, helping explain the complex geometry of the beamlines to a wider audience. An augmented-reality version of the panoramas is being developed as well, enabling firefighters to train for low-visibility scenarios in a safe, controlled environment. Preparations for LS3 also include a series of in-situ inspections throughout the North Area. These involve studying shielding, evaluating scaffolding options, reviewing SCE interfaces and carrying out technical walk-throughs needed for the large-scale work packages planned for 2027–2029. Many of these inspections can only be performed when the tunnels and caverns are accessible, making the YETS the necessary moment to conduct them. Access will be coordinated to ensure that interventions respect both safety boundaries and cross-project planning constraints. Coordinating such a broad set of activities requires careful attention. “With so much happening during this YETS and especially in LS3, and with numerous projects running simultaneously, coordinating the different contractors, service teams and consolidation activities is a real challenge,” explains Xavier Palle, who leads the NA-CONS execution planning for the North Area. “But through close collaboration and regular reviews, we manage to keep the planning fair, and the schedule reliable for everyone involved.” When Run 2026 begins, the results of this season’s work will be visible throughout the North Area: in safer evacuation paths, more robust infrastructure, renewed equipment and a technical environment prepared to support everything from the fixed-target experiments over the large LHC-related test campaigns to detector development in EHN1 and the activities of the Neutrino Platform.
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