CERN has begun the physical work of replacing some of the Large Hadron Collider's most critical magnets. During the current third long shutdown, teams are dismantling sections of the 27-kilometer ring on either side of the ATLAS and CMS detectors. The first magnet interconnection has been cut, marking the formal start of the operation to remove 28 superconducting magnets, including the inner triplets that have been in service since the LHC's original construction between 2005 and 2007.
The inner triplets are groups of three quadrupole magnets that focus particle beams as tightly as possible just before collisions. Tighter beams increase luminosity, meaning more collisions and more data for physicists. The replacement magnets are a major technological step forward: instead of niobium-titanium, they use niobium-tin superconducting coils, producing magnetic fields around 40% stronger. The upgraded triplets will be installed around ATLAS and CMS, where the higher collision rate is particularly important for their physics programs.
The new hardware will not be ready immediately — the first quadrupole for the new triplets is expected to arrive in the tunnel at the start of 2029. In total, the project calls for installing 16 cryostats and 28 cryo-assemblies. CERN officials describe the work as a milestone for the High-Luminosity LHC project and a handover from one generation of accelerator technology to the next. The ALICE and LHCb experiments will keep their existing inner triplets, though those magnets will also be upgraded so all four experiments benefit from the overall luminosity increase.