LHC Injector Upgrade

LHC Injector Upgrade
Name	LHC Injector Upgrade
Acronym	LIU
Location	CERN
Established	2014
Status	Ongoing
Predecessor	Large Hadron Collider
Funding	European Union, member states
Website	CERN

LHC Injector Upgrade

The LHC Injector Upgrade is a coordinated modernization program at CERN to enhance the chain of accelerators that feed the Large Hadron Collider by improving beam brightness, reliability, and intensity. It connects refurbishment and replacement projects across the Proton Synchrotron, Super Proton Synchrotron, and injector complexes to enable higher-luminosity operation for the High-Luminosity Large Hadron Collider. The programme interfaces with experiments, accelerator laboratories, and industrial partners across Europe and beyond.

Background and Rationale

The rationale for the Injector Upgrade traces to strategic decisions driven by demands from the ATLAS experiment, CMS experiment, LHCb experiment, and ALICE experiment for greater integrated luminosity and tailored beam conditions. Early studies by CERN Accelerator School alumni and advisory panels including members from EUROfusion and national laboratories recommended enhancements to the Linear Accelerator 2 and Proton Synchrotron Booster to address space-charge limits and emittance growth observed in operations feeding the Large Hadron Collider. The upgrade responds to roadmaps set by the European Strategy for Particle Physics and coordination with projects such as the High-Luminosity LHC and proposed facilities including the Future Circular Collider. Historical constraints identified during campaigns at Brookhaven National Laboratory and Fermilab informed design choices to mitigate beam loss and improve machine protection, as argued in reports from the LHC Machine Committee and technical reviews by CERN Council delegations.

Design and Technical Components

Major components include a new injection chain module, upgraded radio-frequency systems, and enhanced collimation and diagnostics. The installation of Linac4 replaced Linac2 to provide 160 MeV H- beams into the Proton Synchrotron Booster, enabling lower space-charge tune shifts and improved transverse emittance for downstream transfers to the Proton Synchrotron. Replacement and refurbishment of power converters and vacuum systems in the Super Proton Synchrotron improve reliability and allow optimized bunch structures for ATLAS and CMS. New low-level RF and digital feedback from collaborators at DESY and INFN support longitudinal beam control, while upgrades to the injection and extraction septa draw on expertise from European Organization for Nuclear Research partners and industry suppliers certified under European Committee for Standardization. Beam instrumentation upgrades include tomography systems developed with teams from SLAC National Accelerator Laboratory and KEK to measure transverse and longitudinal profiles, and new beam loss monitors inspired by designs from CERN BE-OP groups.

Upgrade Phases and Timeline

The LIU programme proceeded in staged phases aligned with LHC long shutdowns. Initial civil and equipment work for Linac4 and the PSB began during Long Shutdown 1 and culminated with commissioning in 2017, timed for Run 2 transitions. Further interventions targeted the SPS RF systems and extraction devices during Long Shutdown 2 to prepare for Run 3. Subsequent activities scheduled around Long Shutdown 3 focus on finalizing high-power components, system integration, and validation for the High-Luminosity LHC era. Each phase coordinated shutdown windows, procurement milestones, and commissioning campaigns with stakeholders including the LHC Experiments Committee and national funding bodies like the Swiss Confederation and French Alternative Energies and Atomic Energy Commission.

Performance Goals and Expected Impact

Performance goals include increased bunch intensity, improved brightness, reduced emittance growth, and higher reliability metrics to achieve luminosity objectives for HL-LHC. Targets specified by the LHC Committee aim to double effective luminosity delivery to experiments such as ATLAS and CMS over the HL-LHC lifetime by reducing injection losses and enhancing beam quality. For flavour physics, tailored beam parameters are expected to benefit LHCb's rare-decay sensitivity and time-dependent analyses, while ALICE benefits from improved heavy-ion injection handling. The injector upgrade also yields cross-disciplinary impacts by providing a platform for technology transfer with partners like European Space Agency-linked laboratories and industrial contractors, fostering developments in superconducting technology, power electronics, and control systems.

Technical Challenges and Risks

Challenges include controlling space-charge effects in high-intensity H- injection, mitigating electron cloud phenomena observed in multi-bunch operations, and ensuring reliability of high-voltage power converters under increased duty cycles. Integrating new hardware—such as RF cavities and fast kicker systems—into legacy tunnels requires precise alignment and radiation protection measures developed with CERN Radiation Protection units. Supply chain risks and schedule slips can cascade into LHC availability, as highlighted by contingency analyses from the Project Management Board and independent reviews by organizations including European Investment Bank advisors. Mitigation strategies rely on parallel testing at test stands, redundancy in critical systems, and coordinated risk registers maintained with national laboratories like CERN members and partner institutes.

Project Management and Collaboration

The LIU programme is managed through CERN directorates with governance involving the CERN Council, international collaborations, and in-kind contributions from institutes such as STFC Rutherford Appleton Laboratory, Istituto Nazionale di Fisica Nucleare, and GSI Helmholtz Centre. Project teams operate within formal work packages coordinated by task forces and steering committees that include representatives from the LHC Accelerator Research Program and technical coordination units. Collaborative frameworks underpin procurement, cryogenics integration, and commissioning activities, leveraging knowledge exchange with European XFEL engineers and accelerator experts from Paul Scherrer Institute. The programme emphasizes training and workforce development through internships, secondments, and joint doctoral programmes with universities allied to CERN.

Category:Particle accelerators Category:CERN projects