CERN Accelerating science

Article
Report number	arXiv:1804.07418 ; FERMILAB-PUB-18-084-AD-APC ; FERMILAB-PUB-21-008-AD
Title	Resonant and random excitations on the proton beam in the Large Hadron Collider for active halo control with pulsed hollow electron lenses
Related title	Effects of Resonant and Random Excitations on the Proton Beam in the Large Hadron Collider, with Applications to the Design of Pulsed Hollow Electron Lenses for Active Halo Control
Author(s)	Fitterer, Miriam (Fermilab) ; Stancari, Giulio (Fermilab) ; Valishev, Alexander (Fermilab) ; Redaelli, Stefano (CERN) ; Valuch, Daniel (CERN)
Publication	2021-02-12
Imprint	2018-04-19
Number of pages	24
Note	33 pages, 32 figures, 46 references. Revised manuscript submitted to Phys. Rev. Accel. Beams
In:	Phys. Rev. Accel. Beams 24 (2021) 021001
DOI	10.1103/PhysRevAccelBeams.24.021001
Subject category	physics.acc-ph ; Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN LHC
Project	CERN HL-LHC
Abstract	We present the results of numerical simulations and experimental studies about the effects of resonant and random excitations on proton losses, emittances, and beam distributions in the Large Hadron Collider (LHC). In addition to shedding light on complex nonlinear effects, these studies are applied to the design of hollow electron lenses (HEL) for active beam halo control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable amount of energy will be stored in the beam tails. To control and clean the beam halo, the installation of two hollow electron lenses, one per beam, is being considered. In standard electron-lens operation, a proton bunch sees the same electron current at every revolution. Pulsed electron beam operation (i.e., different currents for different turns) is also considered, because it can widen the range of achievable halo removal rates. For an axially symmetric electron beam, only protons in the halo are excited. If a residual field is present at the location of the beam core, these particles are exposed to time-dependent transverse kicks and to noise. We discuss the numerical simulations and the experiments conducted in 2016 and 2017 at injection energy in the LHC. The excitation patterns were generated by the transverse feedback and damping system, which acted as a flexible source of dipole kicks. Proton beam losses, emittances, and transverse distributions were recorded as a function of excitation patterns and strengths. The resonant excitations induced rich dynamical effects and nontrivial changes of the beam distributions, which, to our knowledge, have not previously been observed and studied in this detail. We conclude with a discussion of the tolerable and achievable residual fields and proposals for further studies.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2021-2025 authors (License: CC-BY-4.0)

Corresponding record in: Inspire