From the LHC to the HiLumi LHC: upgrading of the Cern particle accelerator

The European Organization for Nuclear Research, known as CERN, has initiated a major upgrade to its flagship particle accelerator, the Large Hadron Collider (LHC), marking the beginning of a multi-year shutdown. This phase, referred to as Long Shutdown 3 (LS3), commenced after the completion of the third operational period, called Run 3, on June 29. During this time, scientists conducted their final experiments before the LHC will undergo extensive modifications and enhancements. The facility is expected to resume scientific operations in 2030 following this overhaul. The LHC, located near Geneva, Switzerland, was first activated in 2008 but faced initial challenges due to technical issues that delayed its full operation until 2009. Since then, it has been instrumental in advancing our understanding of fundamental physics. One of its most significant achievements came in 2012 when the ATLAS and CMS experiments confirmed the existence of the Higgs boson, a particle predicted by physicist Peter Higgs in the 1960s. For his theoretical work, Higgs was awarded the Nobel Prize in Physics in 2013. As part of the LS3 upgrades, the LHC will be transformed into the High-Luminosity LHC (HiLumi LHC). This transformation involves increasing the luminosity—the number of collisions occurring at points where particle beams intersect—by a factor of ten. To achieve this, the collider’s detectors must also be upgraded to handle the increased data load and ensure accurate detection of these high-frequency collisions. Additionally, the collision energy will be raised from 13.6 tera-electron volts during Run 3 to 14 tera-electron volts in future operations. These changes are crucial for exploring rare particles and phenomena, which require large datasets to confirm their existence. Markus Klute, a physicist at the Karlsruhe Institute of Technology, explained that the improvements include replacing faulty components, installing new modules, and using more advanced magnet coils. These upgrades aim to enhance both the precision and efficiency of the LHC's operations. According to Jean-Philippe Tock, head of the LS3 coordination team at CERN, the project represents a massive logistical and technical challenge. It involves removing and replacing 1.2 kilometers of magnets and components within the LHC itself, along with numerous other projects across the entire complex. Thousands of engineers, physicists, technicians, and support staff are working on these initiatives. The transition to the HiLumi LHC is part of a broader vision for the future of particle physics research. Plans for a successor to the LHC, the Future Circular Collider (FCC), have been under discussion since 2014. The FCC would be significantly larger than the current LHC, with a circumference of approximately 91 kilometers compared to the LHC's 27 kilometers. While technically feasible, the project requires substantial funding, estimated at around 16 billion euros for the first phase alone. A decision regarding the FCC's implementation is anticipated by 2028. The LHC's upcoming upgrades reflect the continuous evolution of experimental physics, driven by the need to explore deeper questions about the universe. As the HiLumi LHC prepares for its activation in 2030, researchers anticipate new discoveries that could further unravel the mysteries of particle interactions and the fundamental forces governing the cosmos. The LS3 shutdown underscores the complexity and scale of modern scientific endeavors, highlighting the collaborative efforts required to push the boundaries of human knowledge.