Summary
CERN has begun dismantling magnet sections near the ATLAS and CMS experiments as part of the LHC’s third long shutdown. The work prepares for new niobium-tin inner triplets designed to produce magnetic fields about 40% stronger than those of the current magnets.
CERN has begun disconnecting and dismantling sections of the Large Hadron Collider near the ATLAS and CMS experiments to make way for components of the High-Luminosity LHC (HiLumi LHC). Teams started taking apart the sections on 7 September 2026; CERN says the first magnet interconnection was cut during the week of 17 September. The work is part of the accelerator’s third long shutdown, known as LS3.
The upgrade centres on replacing the inner triplets: groups of three quadrupole magnets positioned on either side of the main experiments. CERN Director-General Mark Thomson visited the tunnel at the ATLAS site to mark the start of the operation.
Why the inner triplets matter
The quadrupoles focus the particle beams before they meet inside the detectors. Tighter focusing raises the chance that particles will collide. The rate of collisions over time is called luminosity; higher luminosity gives experiments more collision data to study.
The LHC’s inner triplets were installed during the accelerator’s construction, between 2005 and 2007. CERN says the new versions will use niobium-tin superconducting coils instead of the niobium-titanium magnets now in place. They are designed to produce magnetic fields of 11.3 tesla—about 40% stronger than those of the current magnets.
That stronger focusing is intended to support the LHC’s high-luminosity phase. CERN plans to install the new inner triplets around ATLAS and CMS, whose experiments are central to the replacement work.
The scale and timing of the replacement
The dismantling involves removing 28 superconducting magnets, including the inner triplets, from the sections on either side of ATLAS and CMS. CERN says the upgrade will involve installing 16 cryostats and 28 cryo-assemblies. Cryostats house the superconducting magnet assemblies and their cryogenic systems, which keep them at the low temperatures needed for superconducting operation.
The first quadrupole of the new triplets is expected to reach the tunnel at the start of 2029. The removal now under way is therefore an early step in a larger programme to prepare those sections of the accelerator for the new hardware.
ALICE and LHCb have different physics programmes and operating modes, and CERN says they do not need the same increase in instantaneous luminosity as ATLAS and CMS. They will keep their existing inner triplets, with improvements intended to let both experiments benefit from the luminosity increase.