CERN has begun a major transformation of the Large Hadron Collider (LHC), removing some of its most important superconducting magnets as part of an ambitious upgrade designed to dramatically increase the accelerator’s particle-collision rate.

The work began in September 2026 during the third Long Shutdown of the LHC. Engineers have started disconnecting and dismantling sections around the ATLAS and CMS experiments, preparing them for a new generation of superconducting magnets.

The upgrade is part of the High-Luminosity Large Hadron Collider, commonly known as the HiLumi LHC. The upgraded machine is expected to provide scientists with substantially more collision data, allowing researchers to investigate fundamental questions about matter, energy and the structure of the universe.

Why the Magnets Are So Important

The LHC is a 27-kilometre-long particle accelerator located beneath the Franco-Swiss border region.

Inside the accelerator, powerful magnets guide beams of protons around the circular tunnel at extremely high speeds. Other magnets focus the beams immediately before they collide inside the experiments.

These focusing magnets are known as inner triplets.

The more tightly the particle beams can be focused, the greater the probability that particles will collide. More collisions mean more data for scientists to examine.

The new HiLumi magnets are therefore central to increasing the LHC’s scientific output.

New Magnets Will Be Much More Powerful

The new inner-triplet magnets use niobium-tin superconducting technology, replacing the older niobium-titanium magnets.

They are designed to generate magnetic fields of approximately 11.3 tesla, around 40% stronger than the current magnets, according to CERN.

The magnets also have a significantly larger aperture, allowing them to accommodate the requirements of the higher-luminosity machine.

Their superconducting properties allow them to carry extremely high electrical currents while operating at temperatures close to absolute zero.

28 Magnets to Be Removed

The current upgrade operation involves the removal of 28 superconducting magnets around the ATLAS and CMS experiments.

The work requires teams to carefully disconnect sections of the accelerator before extracting the existing equipment.

In total, the future system will include 16 cryostats and 28 cryo-assemblies, representing a substantial engineering operation underground.

The first quadrupole of the new generation is expected to arrive in the tunnel at the beginning of 2029.

More Collisions, More Data

The primary scientific objective of the upgrade is to increase the LHC’s luminosity.

Luminosity refers to the rate at which potentially useful particle collisions occur.

A higher collision rate gives experiments more opportunities to observe rare physical processes.

Some of these events can be extremely uncommon, meaning that scientists may need enormous numbers of collisions before obtaining enough data to identify them confidently.

The increased data volume could therefore improve measurements of known particles and help researchers search for previously unobserved phenomena.

Searching for New Physics

The LHC has already played a central role in modern particle physics, most famously through the discovery of the Higgs boson in 2012.

The HiLumi upgrade is intended to push the accelerator into a new era of precision and discovery.

Researchers will be able to collect much larger datasets and conduct more detailed studies of the Higgs boson and other fundamental particles.

The increased sensitivity could also help scientists investigate questions that remain unanswered, including the nature of dark matter and possible physics beyond the current Standard Model.

The upgrade itself does not guarantee that a new particle will be discovered. Instead, it increases the amount and quality of experimental information available to scientists.

A Four-Year Transformation

The LHC entered its third Long Shutdown in June 2026 after completing its latest physics run.

During the shutdown, CERN is carrying out extensive maintenance, consolidation and upgrades across the accelerator complex.

More than 1.2 kilometres of the LHC is being dismantled and replaced or modified as part of the transformation.

The broader upgrade programme is expected to continue for several years, with the HiLumi LHC scheduled to restart around 2030.

Other Detector Upgrades Underway

The magnet replacement is only one part of the transformation.

The ATLAS and CMS experiments are also receiving upgraded detector systems capable of handling the enormous increase in collision data expected during the HiLumi era.

At CMS, for example, new electronics are being installed for the muon chambers. The upgraded system is designed to process signals with very high precision and support the experiment’s trigger system as collision rates increase.

The Next Era of Particle Physics

The LHC’s current transformation represents one of the largest upgrades in the accelerator’s history.

The objective is not simply to make the machine more powerful. It is to give scientists access to far more particle collisions and therefore a much larger experimental dataset.

As the new magnets, detectors and supporting systems are installed, the LHC is gradually being prepared for its next scientific chapter.

When the upgraded machine returns to operation, researchers will have a substantially enhanced tool for exploring the smallest known components of matter and investigating some of the biggest unanswered questions about the universe.