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Compensating amplitude-dependent tune-shift without driving fourth-order resonances
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.ORCID iD: 0000-0002-6229-5620
2017 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 869, 1-9 p.Article in journal (Refereed) Published
Abstract [en]

If octupoles are used in a ring to correct the amplitude-dependent tune-shift one normally tries to avoid that the octupoles drive additional resonances. Here we consider the optimum placement of octupoles that only affects the amplitude-dependent tune-shift, but does not drive fourth-order resonances. The simplest way turns out to place three equally powered octupoles with 60° phase advance between adjacent magnets. Using two such octupole triplets separated by a suitable phase advance cancels all fourth-order resonance driving terms and forms a double triplet we call a six-pack. Using three six-packs at places with different ratios of the beta functions allows to independently control all amplitude-dependent tune-shift terms without exciting additional fourth-order resonances in first order of the octupole excitation.

Place, publisher, year, edition, pages
2017. Vol. 869, 1-9 p.
Keyword [en]
Beam dynamics, Nonlinear beam dynamics
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-329979DOI: 10.1016/j.nima.2017.06.047ISI: 000409530200001OAI: oai:DiVA.org:uu-329979DiVA: diva2:1144054
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 2011-6305, 2014-6360
Available from: 2017-09-25 Created: 2017-09-25 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Beam Diagnostics and Dynamics in Nonlinear Fields
Open this publication in new window or tab >>Beam Diagnostics and Dynamics in Nonlinear Fields
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Particle accelerators are indispensable tools for probing matter at the smallest scales and the improvements of such tools depend on the progress and understanding of accelerator physics. The Compact Linear Collider (CLIC) is a proposed, linear electron–­positron collider on the TeV-scale, based at CERN. In such a large accelerator complex, diagnostics and alignment of the beam are crucial in order to maintain beam quality and luminosity. In this thesis we have utilized the nonlinear fields from the octupole component of the radio-frequency fields in the CLIC accelerating structures for beam-based diagnostics. We have investigated methods where the nonlinear position shifts of the beam are used to measure the strength of the octupole component and can also be used for alignment. Furthermore, from the changes in transverse beam profile, due to the nonlinear octupole field, we determine the full transverse beam matrix, which characterizes the transverse distribution of the beam.

In circular accelerators, nonlinear fields result in nonlinear beam dynamics, which often becomes the limiting factor for long-term stability. In theoretical studies and simulations we investigate optimum configurations for octupole magnets that compensate amplitude-dependent tune-shifts but avoid driving fourth-order resonances and setups of sextupole magnets to control individual resonance driving terms in an optimal way.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1583
Keyword
Beam diagnostics, Nonlinear beam dynamics, Accelerator physics
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-330975 (URN)978-91-513-0121-1 (ISBN)
Public defence
2017-12-08, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-11-15 Created: 2017-10-19 Last updated: 2017-11-15

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Ögren, JimZiemann, Volker

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