LHC Injectors Upgrade

LHC Injectors Upgrade. The LHC Injectors Upgrade (LIU) was a major CERN infrastructure project designed to modernize and enhance the chain of pre-accelerators that feed particle beams into the Large Hadron Collider. Its primary objective was to increase the intensity and brightness of proton and ion beams delivered to the LHC, enabling the flagship collider to reach its ultimate design performance. The comprehensive upgrade involved significant modifications to the Proton Synchrotron Booster, the Proton Synchrotron, and the Super Proton Synchrotron, ensuring they could meet the demanding requirements of the High-Luminosity LHC era.

Project overview

Initiated as a critical component of CERN's long-term strategy, the LIU project was essential for overcoming limitations in the existing injector complex that would have constrained the Large Hadron Collider's physics reach. The project was formally approved by the CERN Council and was executed in close coordination with the broader High-Luminosity LHC upgrade program. Key drivers included the need to supply beams with higher intensity to compensate for the reduced number of colliding bunches in the HL-LHC configuration and to improve beam quality for specialized runs, such as those involving lead ions. The successful completion of LIU was a prerequisite for the full exploitation of upgraded experiments like ATLAS and CMS.

Technical scope and components

The technical scope of LIU was extensive, targeting critical subsystems across the entire injector chain. For the Proton Synchrotron Booster, work included the replacement of its radio frequency system and the installation of new beam injection and extraction equipment. The Proton Synchrotron underwent major renovations, including a complete overhaul of its main power supply system, upgrades to its RF cavities, and the implementation of a new beam dumping system to handle higher intensities safely. The Super Proton Synchrotron saw improvements to its injection and acceleration systems, alongside enhancements to its vacuum system to mitigate electron cloud effects. Additionally, the Linac4 accelerator was constructed as a new first link in the chain, replacing the older Linac2 to provide higher-energy protons to the Booster.

Implementation and timeline

The implementation of the LIU project was strategically phased to align with the scheduled long shutdowns of the Large Hadron Collider. Major hardware installation and commissioning took place during Long Shutdown 2, which spanned from 2019 to 2021. This period followed the conclusion of the accelerator's Run 2 and preceded the start of Run 3. Key milestones included the commissioning of Linac4 in 2020 and the gradual return to operation of the upgraded injector chain throughout 2021. The project team, involving hundreds of engineers and technicians from across CERN's departments and collaborating institutes, managed a complex logistics operation to install, test, and validate thousands of new components without compromising the existing infrastructure.

Impact on LHC performance

The impact of the LIU on Large Hadron Collider performance is profound, directly enabling the increased integrated luminosity targets of the HL-LHC program. By delivering beams with approximately double the previous intensity, the upgraded injectors reduce the time required to collect the vast datasets needed for rare physics processes. The enhanced beam brightness and quality also improve the efficiency of collisions within the LHC's interaction points, benefiting all major experiments. For heavy-ion physics, the upgrades allow for more intense beams of lead nuclei, facilitating studies of the quark–gluon plasma under new conditions. This increased performance is critical for precision measurements of the Higgs boson and searches for phenomena beyond the Standard Model.

Collaborating institutions

While CERN served as the host laboratory and project leader, the LIU initiative benefited from substantial contributions from its member states and international partners. Key collaborating institutions included the French Alternative Energies and Atomic Energy Commission, the Italian National Institute for Nuclear Physics, and the German Electron Synchrotron. Numerous national laboratories and universities, such as the University of Oxford and the University of Milan, provided specialized expertise in accelerator physics, superconducting magnet technology, and beam diagnostics. The project also fostered close ties with industrial partners across Europe for the manufacturing of custom components, aligning with CERN's mandate for technological transfer.

Category:CERN Category:Particle accelerators Category:Physics experiments