Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider

TL;DR

This paper discusses methods for precise beam-based aperture measurements in the CERN LHC, demonstrating how these techniques enhance accelerator performance and safety during high-energy operations.

Contribution

The paper introduces and reviews innovative beam-based aperture measurement methods that improved LHC operation and performance in Run 1 and Run 2.

Findings

Enhanced aperture measurement accuracy during high-energy runs

Contributed to increased LHC peak luminosity and operational safety

Validated methods for future accelerator performance optimization

Abstract

The beam aperture of a particle accelerator defines the clearance available for the circulating beams and is a parameter of paramount importance for the accelerator performance. At the CERN Large Hadron Collider (LHC), the knowledge and control of the available aperture is crucial because the nominal proton beams carry an energy of 362 MJ stored in a superconducting environment. Even a tiny fraction of beam losses could quench the superconducting magnets or cause severe material damage. Furthermore, in a circular collider, the performance in terms of peak luminosity depends to a large extent on the aperture of the inner triplet quadrupoles, which are used to focus the beams at the interaction points. In the LHC, this aperture represents the smallest aperture at top-energy with squeezed beams and determines the maximum potential reach of the peak luminosity. Beam-based aperture measurements in these conditions are difficult and challenging. In this paper, we present different methods that have been developed over the years for precise beam-based aperture measurements in the LHC, highlighting applications and results that contributed to boost the operational LHC performance in Run 1 (2010-2013) and Run 2 (2015-2018).