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Aligning linac accelerating structures using a copropagating octupolar mode
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. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.ORCID iD: 0000-0002-6229-5620
2017 (English)In: Physical Review Accelerators and Beams, ISSN 2469-9888, Vol. 20, article id 102801Article in journal (Refereed) Published
Abstract [en]

We propose a novel method to align accelerating structures such as those used in the Compact Linear Collider (CLIC) by exploiting a mode that copropagates with the normal accelerating mode. This mode has an octupolar dependence in the transverse direction and is caused by radial waveguides intended to damp higher-order modes. The nonlinear dependence of the octupolar mode makes it possible to determine the center of the structure from the nonlinear dependence of the transverse kick, observed on a downstream beam position monitor, while changing the transverse position of the beam with respect to the accelerating structures. We discuss the method, its tolerances and disentangling the individual misalignments of two adjacent accelerating structures that are powered from a single source.

Place, publisher, year, edition, pages
College Park, MD: American Physical Society, 2017. Vol. 20, article id 102801
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-331616DOI: 10.1103/PhysRevAccelBeams.20.102801ISI: 000413054500001OAI: oai:DiVA.org:uu-331616DiVA, id: diva2:1149500
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 2011-6305Swedish Research Council, 2014-6360Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2018-01-29Bibliographically 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. p. 87
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1583
Keywords
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: 2018-03-07

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Ögren, JimZiemann, Volker

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