LHC Injector Upgrade (LIU)

LHC Injector Upgrade (LIU)
Name	LHC Injector Upgrade
Abbreviation	LIU
Established	2013
Location	CERN, Geneva
Parent organization	European Organization for Nuclear Research
Purpose	Upgrade of accelerators supplying beams to the Large Hadron Collider

LHC Injector Upgrade (LIU) The LHC Injector Upgrade modernised the chain of accelerators feeding the Large Hadron Collider to deliver higher brightness and intensity proton and ion beams for the High-Luminosity Large Hadron Collider era. Conceived and coordinated at CERN with contributions from institutes across Europe and worldwide, LIU combined hardware refurbishment, new radiofrequency systems, magnet upgrades, and beam diagnostics to replace legacy components dating from the Super Proton Synchrotron era. The programme interfaced with major projects and experiments including ATLAS, CMS, ALICE, and LHCb while aligning with strategic plans from the European Strategy for Particle Physics.

Background and Motivation

LIU originated from performance requirements set by the HL-LHC project and priorities outlined by the Particle Physics Project Prioritization Panel, European Strategy Group, and advisory bodies at CERN Council. Motivations included sustaining operation after long service periods of the PS Booster and Proton Synchrotron, meeting luminosity goals for experiments such as ATLAS and CMS, and enabling advanced heavy-ion programs for ALICE. Historical precedents influencing LIU included upgrades for the Large Electron–Positron Collider and lessons from the Super Proton Synchrotron machine studies, with oversight by committees linked to INFN, STFC, BNL, and IRFU.

Scope and Components

LIU encompassed upgrades to the full injector chain: the LINAC4 injector, the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS), and the Super Proton Synchrotron (SPS), plus transfer lines and beam instrumentation. Major components included new RF cavities inspired by designs at KEK, DESY, and SLAC, broadband feedback systems developed with partners like FNAL and CERN groups, upgraded magnet power converters drawing on heritage from LEP and ISOLDE, and collimation and vacuum improvements with input from GSI, CEA Saclay, and IFIC. The programme also incorporated cryogenics interfaces relevant to HL-LHC cryogenic architectures and coordination with the LHC Machine Advisory Committee.

Upgrades by Accelerator

LINAC4 replaced LINAC2 to provide 160 MeV H- beams, following conceptual links to Spallation Neutron Source injector R&D and accelerator physics at TRIUMF. PS Booster upgrades focused on new injection kickers and harmonic systems similar to those in upgrades at RHIC and PSI, while PS work included longitudinal and transverse control systems paralleling developments at CERN ISOLDE and Uppsala University testbeds. SPS upgrades introduced new RF systems, impedance reduction measures, and transverse dampers informed by operations at Brookhaven National Laboratory and Fermilab. Each machine upgrade drew on accelerator science collaborations with institutions like Imperial College London, ETH Zurich, University of Manchester, TU Darmstadt, and École Polytechnique.

Implementation and Schedule

The LIU timeline ran from initial design phases in the early 2010s through staged installation during long shutdowns coordinated with the LHC schedule, including Long Shutdown 1 and Long Shutdown 2. Project governance used structures similar to large collaborations such as ATLAS and CMS, with technical coordination by CERN Accelerator & Technology Sector and oversight interactions with European Commission-funded consortia and national agencies including CNRS, Max Planck Society, and Academy of Sciences of the Czech Republic. Milestones included LINAC4 commissioning, PS and PSB hardware replacements, and SPS system tests integrated with machine development campaigns alongside teams from JINR and IHEP.

Performance Goals and Expected Impact

LIU targeted increased brightness, reduced beam loss, and higher bunch intensity to satisfy HL-LHC luminosity projections for experiments like ATLAS, CMS, LHCb, and heavy-ion runs for ALICE. Quantitative goals mirrored modelling studies used in the High Luminosity LHC Technical Design Report and simulations in codes from CERN OpenLab collaborations; expected impacts included enabling precision searches tied to theories tested at CERN Theory Department and supporting measurements relevant to the Standard Model and beyond-standard-model searches pursued by groups including Theory Division collaborators. The upgrade aimed to reduce operational risks documented by LHC Machine Committee and improve machine availability comparable to programmes at RHIC and SPS historical operation.

Challenges and Technical Developments

Technical challenges included managing space-charge effects at injection energies, mitigating collective instabilities, and handling higher beam-induced heat loads—issues investigated with beam dynamics studies from PSI, mitigation strategies from Oak Ridge National Laboratory, and impedance modelling practices at DESY. Developments comprised novel RF control algorithms built with software frameworks used in ITER diagnostics, radiation-hard electronics collaborations with ESA-linked contractors, and advanced beam instrumentation employing techniques developed at PETRA III and European XFEL. Risk management addressed supply-chain coordination during procurement linked to vendors in Germany, France, Italy, and the United Kingdom and workforce planning tied to university training programmes at CERN Summer Student Programme.

Legacy and Future Developments

LIU leaves a modernised injector complex that underpins HL-LHC operations and informs next-generation projects such as FCC studies and proposals at CERN Neutrino Platform. Its technical legacy includes RF and beam instrumentation designs transferable to facilities like ESS, SPIRAL2, and upgrades at J-PARC. The collaborative frameworks and industrial partnerships established during LIU continue to influence accelerator R&D consortia, doctoral training networks across European Research Area, and strategic planning in the European Strategy for Particle Physics.

Category:Particle accelerators Category:CERN projects