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| CERN LHC Long Shutdown | |
|---|---|
| Name | CERN LHC Long Shutdown |
| Location | Geneva |
| Type | Major accelerator maintenance and upgrade period |
| Began | 2013 |
| Ended | ongoing |
| Organizer | CERN |
| Participants | ATLAS, CMS, LHCb, ALICE, European Organization for Nuclear Research |
CERN LHC Long Shutdown is a series of planned extended maintenance and upgrade periods for the Large Hadron Collider at CERN designed to improve accelerator performance, reliability, and experimental capability. These shutdowns coordinate work across major detector collaborations such as ATLAS, CMS, LHCb, and ALICE, while interfacing with international partners including ITER, Fermilab, DESY, and national laboratories. The programs align with mandates from governing bodies like the European Commission and advisory panels such as the Particle Physics Project Prioritization Panel and the European Strategy for Particle Physics.
The long shutdowns originated after the discovery of the Higgs boson in 2012 to enable comprehensive upgrades following early operational experience with the Large Hadron Collider. Motivated by goals laid out by panels including the CERN Council, the European Strategy Group, and review committees connected to Institute of Physics reports, the work aims to increase instantaneous luminosity, reduce machine downtime, and modernize systems previously developed by collaborations such as Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and SLAC National Accelerator Laboratory. The program ties into broader initiatives including the High-Luminosity Large Hadron Collider project and international proposals like the Future Circular Collider and the International Linear Collider.
The shutdowns have been organized into multi-year phases correlated with operational runs designated Run 1, Run 2, Run 3, and the High-Luminosity era. Key milestones reference the periods before and after the Higgs boson announcement, coordination with shutdowns at facilities like J-PARC and KEK, and alignment with funding cycles from agencies such as the National Science Foundation and the French Alternative Energies and Atomic Energy Commission. Phases include initial consolidation, major magnet and cryogenics interventions, injector chain refurbishment involving PS Booster and SPS, and final commissioning leading into physics runs used by experiments including ATLAS and CMS.
Works undertaken include replacement and reinforcement of superconducting magnets inspired by developments at laboratories such as Fermilab and KEK, installation of new cryogenic plants, consolidation of radiofrequency systems, and enhancement of beam instrumentation developed in collaboration with institutes like CERN, DESY, and INFN. Major projects encompass the High-Luminosity Large Hadron Collider upgrade of interaction-region magnets, adoption of Nb3Sn technology pioneered with partners including Oak Ridge National Laboratory, and deployment of crab cavities tested at facilities such as JLab and Cornell University. Injectors and transfer lines have seen upgrades tied to work at PS Booster, SPS, and coordination with accelerator physics groups from Imperial College London and MIT.
Detector collaborations used the shutdowns to install new tracking systems, calorimeter electronics, trigger architectures, and radiation-hard sensors developed with input from CERN member-state institutes including CNRS, INFN, STFC, and Max Planck Society. Upgrades to ATLAS inner tracker, CMS high-granularity calorimeter prototypes, LHCb vertex locator replacements, and ALICE time projection chamber refurbishments were synchronized with schedule windows. Work involved coordination with detector technology groups at Berkeley Lab, University of Oxford, University of Cambridge, Università di Padova, and industrial partners such as Siemens and Thales.
Long shutdowns included extensive safety programs following standards from bodies like the International Atomic Energy Agency and national regulators, upgrades to tunnel infrastructure, radiation shielding refurbishment, and improvements to cryogenics and electrical distribution systems. Civil engineering tasks referenced construction practice from projects such as the Gotthard Base Tunnel and collaborations with contractors experienced on European XFEL and ITER. Operational readiness reviews were overseen by panels including representatives from CERN Council, European Strategy Group, and national funding agencies.
Objectives focused on increasing integrated luminosity to enable precision measurements of the Higgs boson, searches for physics beyond the Standard Model, and rare-process studies in flavor physics pursued by LHCb and heavy-ion programs in ALICE. Upgrades aimed to raise peak luminosity, reduce pile-up through improved timing, and enhance detector resolution to probe signatures predicted in extensions such as supersymmetry tests and dark matter searches advocated by international collaborations including ATLAS and CMS. Expected outcomes align with strategic roadmaps from the European Strategy for Particle Physics and recommendations by panels such as the Particle Physics Project Prioritization Panel.
Funding and management were coordinated across CERN member states, observer states, and partner laboratories including United States Department of Energy, Japan Society for the Promotion of Science, National Science Foundation, INFN, CNRS, STFC, and agencies from Germany, Italy, France, Spain, and Switzerland. Program governance combined technical boards, resource review committees, and collaboration councils drawn from institutions such as Princeton University, University of Chicago, Massachusetts Institute of Technology, University of Tokyo, and University of Toronto. Procurement and industrial partnerships paralleled projects like European XFEL and ITER, while outreach and educational activities involved universities and institutes across the European Research Area.