The Large Hadron Collider (LHC) — the world's most powerful particle accelerator, a machine that smashes particles together to study the building blocks of the Universe — has been switched off as CERN, the European laboratory for particle physics, begins a major upgrade programme.
The shutdown marks the start of Long Shutdown 3 (LS3), an extensive period of maintenance, consolidation and installation work that will continue until the end of the decade. The programme is intended to prepare the accelerator complex for the High-Luminosity Large Hadron Collider (HiLumi LHC), which is scheduled to begin operations in 2030.
According to a recent blog by CERN, the LHC has been in operation since circulating its first particle beams in 2008 and has played a central role in particle physics research. During three operational runs, the accelerator generated unprecedented volumes of data for experiments investigating the fundamental structure of matter and the Universe.
Its most widely recognised scientific achievement came in 2012, when the ATLAS and CMS collaborations announced the discovery of the Higgs boson, a particle that helps explain why other fundamental particles have mass, confirming a long-standing prediction of the Standard Model, the scientific theory describing the fundamental particles and forces of nature.
Since then, the collider has contributed to the discovery of dozens of new hadrons, studies of matter and antimatter, investigations into quark-gluon plasma and measurements with implications for astrophysics, as per CERN.
In a blog post on June 29, Oliver Brüning, CERN Director for Accelerators and Technology said, “For nearly two decades, it has transformed our understanding of the Universe and inspired generations of scientists, engineers and citizens around the world. Today we say goodbye to the LHC as we have known it, while preparing to welcome its successor: the HiLumi LHC, which will extend this scientific adventure far into the future.”
According to CERN, the upgraded accelerator will increase the collider's luminosity — the number of particle collisions it can generate — by up to ten times, allowing researchers to collect much larger amounts of data.
LS3 is the largest intervention on CERN's accelerator complex since the LHC was constructed. Over the coming years, thousands of scientists, engineers and technicians from CERN and partner institutions will replace major components, modernise experimental facilities and carry out infrastructure upgrades across the laboratory.
Although particle beams will not circulate during the shutdown, scientific work will continue. Researchers will analyse data collected during previous LHC runs while preparing the upgraded experiments for future operations.
CERN expects the accelerator complex to begin restarting gradually from 2028, ahead of the High-Luminosity Large Hadron Collider entering full scientific operation in 2030.
