CERN Powers Down the Large Hadron Collider for a $1.5 Billion Upgrade

The World's Most Powerful Collider Falls Silent

On Monday, CERN switched off the Large Hadron Collider, the 27-kilometre particle accelerator buried beneath the French-Swiss border. The shutdown marks the start of Long Shutdown 3, a four-year programme that will rebuild the machine into the High-Luminosity LHC, or HL-LHC. It brings to a close 18 years of operations for the collider in its current form.

A Legacy Built on the Higgs

During that run, the LHC delivered some of the most important results in modern physics, most famously the 2012 discovery of the Higgs boson by the ATLAS and CMS collaborations. The machine's final physics season began in March 2026, with proton beams colliding at 13.6 TeV and running through the end of June before the switch-off.

What the Upgrade Involves

The overhaul is expected to cost 1.2 billion Swiss francs, roughly $1.5 billion. Thousands of experts will work across CERN's sites and tunnels, replacing every component within a 1.2-kilometre stretch of the ring. Central to the work are new 11 to 12 tesla superconducting magnets and superconducting "crab" cavities, which tilt the particle bunches to maximise collisions at the ATLAS and CMS detectors.

Ten Times the Data

The revamped HL-LHC is scheduled to begin operations in 2030 and run for roughly a decade. It will increase luminosity, the rate of particle collisions, by up to a factor of ten, dramatically expanding the data available to physicists. That flood of data will sharpen measurements of the Higgs boson and widen the search for physics beyond the Standard Model, including dark matter, extending the discovery range for new particles by 20 to 30 percent.

Not an Ending, but a Transformation

CERN has stressed that this is a rebirth rather than a retirement. "It's a big upgrade and a good investment," said Lucio Rossi, the HL-LHC project leader. "It will double the lifetime of the LHC up to 2040." Parts of the accelerator complex will restart from mid-2028, while analysis of the final run's data continues throughout the shutdown.