CERN Accelerating science

Article
Title	Effects of cavity pre-detuning on RF power transients at injection into the LHC
Author(s)	Karlsen-Baeck, B E (CERN ; Rome U.) ; Argyropoulos, T (CERN) ; Butterworth, A (CERN) ; Calaga, R (CERN) ; Karpov, I (CERN) ; Timko, H (CERN) ; Zampetakis, M (CERN)
Publication	2024
Number of pages	8
In:	JINST 19 (2024) T04005
In:	68th ICFA Advanced Beam Dynamics workshop on high-Intensity and High-Brightness Hadron Beams (HB 2023), CERN, Geneva, Switzerland, 9 - 13 Oct 2023, pp.T04005
DOI	10.1088/1748-0221/19/04/T04005
Subject category	Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN LHC
Abstract	At injection into the Large Hadron Collider (LHC), the radiofrequency (RF) system is perturbed by beam-induced voltage resultingin strong RF power transients and the instant detuning of thecavities. The automatic tuning system, however, needs time for themechanical compensation of the resonance frequency to takeplace. Acting back on the beam, the transients in RF power areexpected to limit the maximum injected intensity by generatingunacceptable beam loss. Reducing them is therefore essential toreach the target intensity during the High Luminosity (HL) LHCera. At LHC flat bottom, the cavities are operated using thehalf-detuning beam-loading compensation scheme. As implementedtoday, the tuner control algorithm starts acting only after theinjection of the first longer bunch train which causes the bunchesfor this injection to experience the largest power spikes. Thiscontribution presents an adapted detuning scheme for the RF cavitiesbefore injection. It was proposed as a path to decrease thetransients, hence increasing the available intensity margin for theavailable RF power. The expected gain is evaluated in particletracking simulations and measurements acquired during operation.
Copyright/License	publication: © 2024-2025 The Author(s) (License: CC-BY-4.0)

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