CERN is beginning the most ambitious upgrade in its history, initiating Long Shutdown 3 and preparing to dismantle 1.2 kilometers of the Large Hadron Collider (LHC) to make way for the HiLumi LHC equipment. Since first circulating beams in September, the LHC has delivered large quantities of data across Runs 1, 3, becoming a discovery machine and pushing the frontiers of science and technology. The accelerator’s most celebrated achievement came on July 4, when the ATLAS and CMS Collaborations announced the discovery of the Higgs boson, confirming a theory proposed nearly half a century earlier. “The LHC has exceeded every expectation,” said Oliver Brüning, CERN Director for Accelerators and Technology. “For nearly two decades, it has transformed our understanding of the Universe and inspired generations of scientists, engineers and citizens around the world.”
LHC Concludes Run 3 and Enters Long Shutdown 3
The scale of the undertaking is now visible as the Large Hadron Collider concluded Runs 1, 3 and entered Long Shutdown 3; teams are actively dismantling 1.2 kilometers of the accelerator to accommodate the forthcoming HiLumi LHC equipment. This is not merely routine maintenance, but a substantial physical deconstruction signaling a transition to the next phase of particle physics exploration. Beyond key results, the LHC facilitated investigations into matter-antimatter imbalance and the properties of quark-gluon plasma, impacting fields from astrophysics to computing. The ATLAS and CMS experiments are undergoing comprehensive upgrades to handle the anticipated increase in collision rates; the HiLumi LHC is projected to increase luminosity by a factor of up to ten, demanding detectors capable of processing over five billion interactions per second. Although particle beams are shut down, analysis of existing LHC data will continue, preparing for a new era of high-energy physics when the upgraded complex restarts, promising deeper insights into the fundamental laws governing the cosmos.
The HiLumi LHC, scheduled to begin operation in 2029, will increase the collider’s luminosity by a factor of up to ten beyond its original design.
HiLumi LHC Upgrade: Installation of New Equipment & Technologies
The cessation of operations for the Large Hadron Collider marks not an end, but a transition toward a substantial overhaul designed to increase its capabilities. Currently, teams are engaged in the meticulous dismantling of 1.2 kilometers of the accelerator. This is not simply routine maintenance; it’s a complex undertaking involving thousands of specialists from CERN and collaborating institutions worldwide, all focused on transforming the LHC into its high-luminosity successor. Beyond the physical removal of magnets and components, the upgrade encompasses a comprehensive renovation of the entire accelerator complex and experimental facilities. Projects range from consolidating the Super Proton Synchrotron (SPS) North Area to transforming the Experimental Cavern North 3 into a high-intensity fixed-target facility, demonstrating the breadth of the LS3 program.
These experiments will need to process between 140 and 200 proton, proton collisions per bunch crossing, a substantial leap from the approximately 60 observed during the last LHC run, necessitating the complete replacement of their trigger systems and the implementation of advanced detector technologies. These new technologies include all-silicon tracking systems boasting billions of readout channels, high-precision timing detectors capable of resolutions measured in tens of picoseconds, and calorimeter systems designed to operate at megahertz rates. “The LS3 represents a huge and complex logistical and engineering undertaking,” says Jean-Philippe Tock, Head of the LS3 Coordination Team.
In the LHC alone, 1.2 km of magnets and components will be removed and replaced with new equipment, and across the whole complex, dozens of projects are planned, involving thousands of engineers, physicists, technicians and support personnel.
Jean-Philippe Tock, Head of the LS3 Coordination Team
Higgs Boson Discovery and LHC’s Scientific Achievements
Following the completion of three operational periods (Runs 1, 3), delivering large quantities of data, the Large Hadron Collider has entered a period of significant transformation with the start of Long Shutdown 3. This pause is not simply maintenance; it’s a substantial physical deconstruction, with 1.2 kilometers of the accelerator being dismantled. This achievement, announced by the ATLAS and CMS Collaborations, propelled the accelerator into a unique position as a discovery machine, facilitating over 85 hadron discoveries and setting limits on the existence of new particles. Beyond key results, the LHC spurred innovation in diverse fields, from accelerator science and superconducting technologies to computing and international collaboration.
The LHC has exceeded every expectation.
Oliver Brüning, CERN Director for Accelerators and Technology
