CERN Accelerating science

Article
Report number	arXiv:2106.09656
Title	Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider
Author(s)	Fuster-Martínez, N. (Valencia U., IFIC ; CERN) ; Aßmann, R.W. (DESY) ; Bruce, R. (CERN) ; Giovannozzi, M. (CERN) ; Hermes, P. (CERN) ; Mereghetti, A. (CERN) ; Mirarchi, D. (CERN) ; Redaelli, S. (CERN) ; Wenninger, J. (CERN)
Publication	2022-03-04
Imprint	2021-06-17
Number of pages	21
Note	21 pages, 14 figures
In:	Eur. Phys. J. Plus 137 (2022) 305
DOI	10.1140/epjp/s13360-022-02483-3
Subject category	physics.acc-ph ; Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN LHC
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).
Copyright/License	preprint: (License: CC BY-NC-SA 4.0) publication: © 2022-2025 The Author(s) (License: CC-BY-4.0)

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