By Federico Roncarolo (CERN)
As a milestone of the HL-LHC Beam Halo Working Group activities, on the 18th of December 2024 a review of the HL-LHC beam halo monitoring system—one of the deliverables of the HL-LHC Project Work Package 13—took place at CERN.
The review panel was chaired by Ubaldo Iriso from CELLS (Spain) and comprised Giovanni Rumolo (BE-ABP), Jorg Wenninger (BE-OP), and Markus Zerlauth (ATS-DO).
The review brought together experts from various CERN departments to evaluate the functional specifications and proposed technical solutions for beam halo monitoring in the High-Luminosity LHC era.
The agenda covered multiple aspects of the system, including the comprehensiveness of functional specifications, technical solutions proposed for implementation during Long Shutdown 3 (LS3), and their associated risks.
The discussions, also based on the presented experience with LHC Run2 beam halo measurements via destructive collimator scans, highlighted the complexity of beam halo monitoring, particularly the distinct requirements for measuring beam tails near the core versus near collimators, and the importance of continuous, non-destructive, monitoring capabilities.
The review addressed several key technical aspects, particularly the need for bunch-by-bunch measurements and how system interlock specifications would complement existing beam loss monitoring systems.
The review examined resource implications and implementation strategies for various monitoring instruments, including Beam Synchrotron Radiation (BSR) detectors, Beam Gas Ionization (BGI) monitors, and Beam Gas Curtain (BGC) systems. Presentations and discussions included options for beam optics tuning at the monitor locations, along with ongoing R&D on low-density materials and their applications with wire scanners for halo monitoring.
The panel members will reconvene in early January 2025 to further discuss their findings and will subsequently produce a comprehensive report with detailed recommendations. This report will help guide the development and implementation of the beam halo monitoring system, which is crucial for the successful and safe operation of the HL-LHC.