MOPM020

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URL	https://doi.org/10.18429/JACoW-IPAC25-MOPM020
Title	Investigation of octupolar resonances in the LHC
Authors	S. Horney, E. Maclean, F. Carlier, F. Soubelet, J. Keintzel, J. Dilly, L. Deniau, M. Le Garrec, R. Tomas, T. Persson European Organization for Nuclear Research P. Burrows University of Oxford, John Adams Institute V. Ferrentino University of Naples Federico II, European Organization for Nuclear Research
Abstract	During operation for luminosity production, the LHC runs with very strong Landau octupoles to ensure the collective stability of the beams. A disadvantage of this is that these octupoles can drive resonances which can be detrimental to beam lifetime. Recently, a special optics configuration has been utilised to reduce the impact of the main octupoles on lifetime. This design relies on correctly modelling the resonance driving term (RDT) response to changes in these magnetic circuits. This paper presents beam-based studies comparing the RDT response to simulations where large discrepancies were found. To try and understand the source of this, several approaches were taken. Various methods including individual circuit measurements, studies of other circuits, and tests at different energy were employed but it remained challenging to localise the source of the discrepancy around the ring. This paper presents an attempt to apply and extend a segment-by-segment method, that has been very effective at identifying local linear optics errors, to non-linear errors through analysis of RDTs.
Paper	download: MOPM020.pdf
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Conference	16th International Particle Accelerator Conference
Series
Location	Taipei, Taiwan
Date	01-06 Jun 2025
Publisher	JACoW Publishing, Geneva, Switzerland
Editorial Board	* Ming-Chyuan Lin - National Synchrotron Radiation Research Center * Yoichi Sato - KEK * Jui-Che Huang - National Synchrotron Radiation Research Center * David Button - Australian Nuclear Science and Technology Organisation * Ping-Shun Chuang - National Synchrotron Radiation Research Center
Online ISBN	978-3-95450-248-6
Online ISSN	2673-5490
Received	27 May 2025
Revised	30 May 2025
Accepted	01 June 2025
Issued	06 June 2025
DOI	10.18429/JACoW-IPAC25-MOPM020
Pages	319-322
Copyright	Published by JACoW Publishing under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s), the published article's title, publisher, and DOI.