The Large Hadron Collider (LHC), the world's most powerful atom smasher, has been switched off by CERN for a significant upgrade aimed at dramatically increasing its scientific output. The particle accelerator entered a four-year shutdown period following its final experiment, with plans to return in 2030 as the High-Luminosity LHC (HiLumi LHC).
This extensive upgrade focuses on increasing the collider's "luminosity," which refers to the number of particle collisions it can generate per unit of time and area. Upon completion, the HiLumi LHC is anticipated to have ten times the luminosity of its predecessor, enabling scientists to collect approximately 100 times more data. The project is estimated to cost around $1.5 billion (£1.29 billion), funded by CERN membership fees and contributions from countries including the United States, Japan, Canada, and China.
Scientists believe this investment is crucial for uncovering fundamental secrets of the universe. The LHC, located in a 27-kilometer (16.8-mile) tunnel beneath the Swiss-French border, began operations in 2008 and has been instrumental in advancing our understanding of particle physics. During its operational runs, the collider has provided unprecedented insights into the fundamental reality of the universe, most notably leading to the discovery of the Higgs Boson in 2012.
The upgrade involves replacing over 1.2 kilometers of magnets and requires significant modifications to the surrounding infrastructure to handle the increased power. The HiLumi LHC will generate a much higher rate of collisions, potentially between 140 and 200 proton collisions each time particle bunches cross, up from the previous rate of 60. This will result in more than five billion collisions per second, producing a massive volume of data. To manage this influx, the new LHC will utilize upgraded detectors equipped with AI systems to identify and store the most significant events.
The HiLumi LHC is scheduled to begin gradually restarting operations in 2028, with the first collisions expected around 2030. In the interim, researchers will analyze the vast datasets collected during the LHC's previous runs. Once operational, scientists hope the enhanced collider will help address some of the most pressing questions in science, including the mysteries of the subatomic world, antimatter, and the early universe. A key objective is to probe and identify new particles that could explain the balance between ordinary matter, dark matter, and dark energy, which together constitute the vast majority of the universe's mass and energy.
Oliver Brüning, CERN Director for Accelerators and Technology, stated that the LHC has "exceeded every expectation" and "transformed our understanding of the Universe." He added, "Today we say goodbye to the LHC as we have known it, while preparing to welcome its successor: the HiLumi LHC."
The project is described by Jean-Philippe Tock, Head of the LS3 Coordination Team, as a "huge and complex logistical and engineering undertaking" involving thousands of personnel. The upgrade is expected to allow researchers to collect vastly larger datasets, measure the Higgs boson in greater detail, study rare processes, and increase the chances of discovering new physics beyond the Standard Model. The HiLumi LHC could produce approximately 380 million Higgs bosons over its lifetime, compared to about 55 million produced since the LHC's inception.