The third long shutdown (LS3) of the CERN accelerator complex

TThe Large Hadron Collider (LHC) operation began in 2008. Its superconducting equipment requires a cool-down/warm-up cycle lasting several months to access some key elements such as superconducting magnets, making annual shutdowns impractical and obliged for a change in programmed stops paradigm. A new lifecycle management approach for programmed stops was therefore necessary. The large interventions were grouped and performed during long shutdowns (LSs). They include maintenance, consolidation and upgrades. LSs last about three years and are scheduled typically every six years. Since the LHC depends on its chain of preceding injectors, this approach was extended to the entire CERN accelerator complex. This paper briefly outlines the methodology used to plan, prepare and coordinate these LSs and presents the interventions and main upgrades planned for the upcoming LS3, scheduled to start mid-2026 for the LHC. The paper highlights various projects, aimed at improving safety, performance, and operational availability as well as implementing new technologies and providing new facilities for the particle physics community.