The Second Long Shutdown of the LHC and Its Injectors: Feedback from the Accelerator Coordination and Engineering Group

The operation of the Large Hadron Collider (LHC) at CERN started in September 2008. Every 5 or 6 years, Long Shutdowns (LS) are programmed to execute time-intensive ordinary and extra-ordinary maintenance of the LHC and its injectors. The second LS (LS2) started in December 2018 and was completed end 2020 for the injectors and early 2022 for the LHC. A huge number of maintenance, consolidation and upgrade activities, especially the upgrade of the injectors complex, were performed with challenges at various levels, from technical, to organizational and managerial. This paper presents the applied methodology put in place by the Accelerator Coordination & Engineering (EN-ACE) Group, in charge of the technical coordination of the activities for the interventions and changes to the LHC and its injectors, to ensure that the installation activities are performed safely, meeting the required high level of quality, while optimizing the schedule. It highlights key points of success and lessons learnt in terms of general coordination, quality assurance, configuration and layout management, spatial integration, planning and scheduling, operational safety, logistics and worksite coordination