CERN Shuts Down the Large Hadron Collider: The Countdown to 2030 Begins

The CERN has halted today, June 29, 2026, the Large Hadron Collider (LHC), the world's most powerful particle accelerator. With the last physics run archived, the Geneva laboratory has opened the Long Shutdown 3 (LS3): the maintenance, consolidation, and upgrade program that will lead the infrastructure towards its new incarnation, the HiLumi LHC.

Operational since September 2008, with the first proton-proton collisions recorded in 2009, the LHC has gone through three operational cycles (Run 1, 2, and 3), accumulating an unprecedented amount of data for the accompanying experiments. The most famous result remains the discovery of the Higgs boson, announced on July 4, 2012, by the ATLAS and CMS collaborations, confirming a mechanism theorized almost fifty years earlier.

In the following years, the accelerator has enabled the identification of over 85 hadrons, imposed exclusion limits on the search for new particles, and conducted investigations into the imbalance between matter and antimatter and quark-gluon plasma. "The LHC has exceeded all expectations," said Oliver Brüning, CERN Director for Accelerators and Technology. "For almost twenty years, it has transformed our understanding of the Universe: today we say goodbye to the LHC as we have known it, while we prepare to welcome its successor."

What Changes with HiLumi LHC

The successor will be HiLumi LHC, which will start operating in 2030 and will increase the collider's luminosity up to ten times beyond the original design. This means much larger datasets, useful for studying the Higgs boson with precision and searching for phenomena that the Standard Model does not explain.

The LS3 is the most extensive intervention on the CERN accelerator complex since the construction of the LHC itself. Until 2030, thousands of technicians, physicists, and engineers from CERN and partner institutes will be working. Within just the LHC, 1.2 kilometers of magnets and components will be dismantled and replaced, while dozens of projects are planned throughout the complex: from consolidating the North Area of the Super Proton Synchrotron to transforming cavern ECN3 into a high-intensity fixed-target facility, to renewing the ISOLDE facility.

"The LS3 represents a huge and complex logistical and engineering undertaking," explains Jean-Philippe Tock, head of the LS3 coordination team. "In just the LHC, 1.2 km of magnets and components will be removed and replaced, and throughout the complex, dozens of projects involving thousands of engineers, physicists, technicians, and support staff are planned."

The ATLAS and CMS detectors will be virtually rebuilt from scratch. With the HiLumi LHC, they will need to handle between 140 and 200 proton-proton collisions for each beam crossing, compared to about 60 from the last run, selecting the most interesting events among over five billion interactions per second. Both experiments will completely replace their trigger systems and adopt fully silicon trackers with billions of readout channels, time detectors with resolutions of a few tens of picoseconds, and calorimeters capable of operating at megahertz frequencies.

Without circulating beams, CERN's scientific activity does not stop: thousands of researchers will continue to analyze the data collected during the LHC era, while simultaneously preparing experiments for the next phase. The accelerator complex will gradually resume operation from 2028, in anticipation of the new chapter opened by the HiLumi LHC.