CERN has officially kicked off a major upgrade of the Large Hadron Collider (LHC) by disconnecting critical components, marking the start of the third long shutdown (LS3). This extensive maintenance period will see the replacement of key magnets with a new, more powerful generation designed to boost the collider's performance significantly.
The LHC, a colossal 27-kilometer ring, relies on thousands of specialized magnets to guide its particle beams. Among the most vital are the "inner triplets," groups of three quadrupole magnets that precisely focus particle beams for collisions within the LHC's main experiments. This focusing is crucial for increasing the collider's luminosity, which directly translates to a higher number of particle collisions and, consequently, more data for researchers.
The centerpiece of the High-Luminosity LHC (HiLumi LHC) project is the installation of these next-generation inner triplets. These new magnets, utilizing niobium-tin superconducting coils instead of the current niobium-titanium, can generate magnetic fields that are approximately 40% stronger, reaching 11.3 tesla. This upgrade is particularly important for the ATLAS and CMS experiments, where the demand for higher collision rates is greatest.
The process began with the cutting of the first magnet interconnection, a symbolic moment attended by CERN Director-General Mark Thomson. "The replacement of these magnets with the new HiLumi LHC inner triplets is crucial for the coming high-luminosity years," stated Jean-Philippe Tock, Head of the LS3 Coordination Team. "The first quadrupole of the new triplets should arrive in the tunnel at the start of 2029." In total, 16 cryostats and 28 cryo-assemblies will be installed.
Since September 7, teams have been working diligently to dismantle sections of the collider around the ATLAS and CMS experiments, aiming to remove 28 superconducting magnets, including the inner triplets. These magnets have been integral to the LHC's operation since its construction. "Today's event is a major milestone for CERN, especially for the HiLumi LHC project team," commented Markus Zerlauth, the HiLumi LHC Project Leader. "The current inner triplets date back to the LHC construction phase and were installed in the machine between 2005 and 2007. After nearly twenty years of operation, they will give way to a new generation of even more powerful magnets."
While the ALICE and LHCb experiments have different operational needs and physics goals, their existing inner triplets will also be upgraded to benefit from the overall increase in LHC luminosity, ensuring that all experiments can take advantage of the enhanced capabilities.
