Beam Cleaning and Collimation Systems
Stefano Redaelli
TL;DR
The paper addresses how to design and operate multistage beam collimation systems for high-energy hadron accelerators to safely intercept unavoidable beam losses and prevent magnet quenches. Using the LHC and its HL-LHC upgrade as primary case studies, it discusses the multistage cleaning concept, aperture modeling, loss assumptions, and performance targets. It documents the LHC layout, the operational challenges encountered, and the achieved cleaning performance that sets a benchmark for future systems. It concludes with transferable guidelines for future colliders and lepton machines, emphasizing integrated approaches to background mitigation and high machine availability.
Abstract
Collimation systems in particle accelerators are designed to safely and efficiently dispose of unavoidable beam losses during operation. Their specific roles vary depending on the type of accelerator. The state of the art in hadron beam collimation for high-intensity, high-energy superconducting colliders is exemplified by the system implemented at the CERN Large Hadron Collider (LHC). In this machine, the stored beam energy reaches levels several orders of magnitude higher than the tiny energy required to quench superconducting magnets. It also exceeds by orders of magnitude the damage thresholds of typical accelerator components, placing stringent demands on beam loss control. Collimation systems are therefore essential for the reliable daily operation of modern accelerators. This lecture reviews the design of a multistage collimation system, using the LHC as a case study. The LHC collimation system has achieved unprecedented cleaning performance, with a level of complexity unmatched by any other accelerator. Design aspects and operational challenges of such large-scale collimation systems are also discussed.