CERN Begins Replacing LHC Magnets in Historic Upgrade

After nearly two decades of service, the Large Hadron Collider is getting a major hardware overhaul. In September, CERN teams began the meticulous process of removing 28 superconducting magnets from the world’s most powerful particle accelerator, marking the formal start of the High-Luminosity LHC (HiLumi LHC) upgrade project.

The operation represents far more than routine maintenance. These magnets, installed between 2005 and 2007 during the LHC’s original construction, have been fundamental to the machine’s ability to smash particles together and unlock the secrets of the universe. Now they’re making way for a new generation of even more powerful equipment.

Why These Magnets Matter

The LHC’s 27-kilometer ring contains thousands of magnets working in concert, but the inner triplets hold special importance. These groups of three quadrupole magnets sit near the four main experiments and perform one critical job: focus particle beams as tightly as possible just before collision. Think of them as the final lens in a microscope, compressing the beams to maximize the chances that particles actually hit each other.

Tighter beam compression directly translates to more collisions. More collisions mean more data for physicists to analyze. In the world of particle physics, luminosity, the number of collisions occurring in a given time period, is everything.

The Technological Leap Forward

The replacement magnets represent a significant technological advance. The current inner triplets use niobium-titanium superconducting coils. The new ones switch to niobium-tin, a material that allows for substantially stronger magnetic fields reaching 11.3 tesla, roughly 40 percent more powerful than what the current magnets can produce.

This upgrade concentrates on the ATLAS and CMS experiments, where the increased collision rate will have the greatest scientific impact. The other two experiments, ALICE and LHCb, operate under different physics programs and don’t require the same instantaneous luminosity boost. However, their existing inner triplets will still receive upgrades so they benefit from the overall luminosity increase across the entire facility.

Jean-Philippe Tock, Head of the LS3 Coordination Team, emphasizes the scale of the undertaking. “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,” he explained. This isn’t a quick swap; it’s a complex engineering project occurring during the third long shutdown.

A Milestone for Modern Science

CERN Director-General Mark Thomson visited LHC Point 1 to witness the historic moment when crews cut the first magnet interconnection. Markus Zerlauth, the HiLumi LHC Project Leader, captured the significance: “After nearly twenty years of operation, they will give way to a new generation of even more powerful magnets. It’s truly remarkable to witness such a handover from one generation of innovation to the next.”

This sentiment reflects something profound about scientific progress. The magnets being removed aren’t failures; they’ve performed exactly as designed for two decades, enabling groundbreaking discoveries including the Higgs boson. Yet technology evolves. What was cutting-edge in 2005 becomes the foundation for something better.

The work is taking place during LS3, one of CERN’s scheduled maintenance periods where the accelerator shuts down for upgrades and repairs. Since September 7, teams have been systematically dismantling sections on either side of ATLAS and CMS, removing equipment that helped reshape our understanding of particle physics.

The new inner triplets represent years of research and development. They’re not merely incremental improvements but genuine innovations that will enable higher collision rates, faster data accumulation, and deeper insights into the fundamental nature of reality. When that first quadrupole arrives in the tunnel in 2029, it will symbolize humanity’s commitment to pushing the boundaries of what we know about the universe.

Materials provided by CERN. Original written by Anaïs Schaeffer.