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Longitudinal Phase Space Tomography with Space Charge

Tomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the non-linearity of large-amplitude sync...

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Detalles Bibliográficos
Autores principales: Hancock, S, Koscielniak, Shane Rupert, Lindroos, M
Lenguaje:eng
Publicado: 2000
Materias:
Acceso en línea:https://dx.doi.org/10.1103/PhysRevSTAB.3.124202
http://cds.cern.ch/record/468153
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author Hancock, S
Koscielniak, Shane Rupert
Lindroos, M
author_facet Hancock, S
Koscielniak, Shane Rupert
Lindroos, M
author_sort Hancock, S
collection CERN
description Tomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the non-linearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method is a hybrid one which incorporates particle tracking. Hitherto, a very simple tracking algorithm has been employed because only a brief span of measured profile data is required to build a snapshot of phase space. This is one of the strengths of the method, as tracking for relatively few turns relaxes the precision to which input machine parameters need to be known. The recent addition of longitudinal space charge considerations as an optional refinement of the code is described. Simplicity suggested an approach based on the derivative of bunch shape with the properties of the vacuum chamber parametrized by a single value of distributed reactive impedance and by a geometrical coupling coefficient. This is sufficient to model the dominant collective effects in machines of low to moderate energy. In contrast to simulation codes, binning is not an issue since the profiles to be differentiated are measured ones. The program is written in Fortran 90 with High-Performance Fortran (HPF) extensions for parallel processing. A major effort has been made to identify and remove execution bottlenecks, for example by reducting floating-point calculations and re­coding slow intrinsic functions. A pointer-like mechanism which avoids the problems associated with pointers and parallel processing has been implemented. This is required to handle the large, sparse matrices that the algorithm employs. Results obtained with and without the inclusion of space charge are presented and compared for proton beams in the CERN PS Booster. Comparisons of execution times on different platforms are presented and the chosen solution for our application program, which uses a dual processor PC for the number crunching, is described.
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institution Organización Europea para la Investigación Nuclear
language eng
publishDate 2000
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spelling cern-4681532021-11-11T09:53:02Zdoi:10.1103/PhysRevSTAB.3.124202http://cds.cern.ch/record/468153engHancock, SKoscielniak, Shane RupertLindroos, MLongitudinal Phase Space Tomography with Space ChargeAccelerators and Storage RingsTomography is now a very broad topic with a wealth of algorithms for the reconstruction of both qualitative and quantitative images. In an extension in the domain of particle accelerators, one of the simplest algorithms has been modified to take into account the non-linearity of large-amplitude synchrotron motion. This permits the accurate reconstruction of longitudinal phase space density from one-dimensional bunch profile data. The method is a hybrid one which incorporates particle tracking. Hitherto, a very simple tracking algorithm has been employed because only a brief span of measured profile data is required to build a snapshot of phase space. This is one of the strengths of the method, as tracking for relatively few turns relaxes the precision to which input machine parameters need to be known. The recent addition of longitudinal space charge considerations as an optional refinement of the code is described. Simplicity suggested an approach based on the derivative of bunch shape with the properties of the vacuum chamber parametrized by a single value of distributed reactive impedance and by a geometrical coupling coefficient. This is sufficient to model the dominant collective effects in machines of low to moderate energy. In contrast to simulation codes, binning is not an issue since the profiles to be differentiated are measured ones. The program is written in Fortran 90 with High-Performance Fortran (HPF) extensions for parallel processing. A major effort has been made to identify and remove execution bottlenecks, for example by reducting floating-point calculations and re­coding slow intrinsic functions. A pointer-like mechanism which avoids the problems associated with pointers and parallel processing has been implemented. This is required to handle the large, sparse matrices that the algorithm employs. Results obtained with and without the inclusion of space charge are presented and compared for proton beams in the CERN PS Booster. Comparisons of execution times on different platforms are presented and the chosen solution for our application program, which uses a dual processor PC for the number crunching, is described.CERN-PS-2000-068-OPoai:cds.cern.ch:4681532000-10-03
spellingShingle Accelerators and Storage Rings
Hancock, S
Koscielniak, Shane Rupert
Lindroos, M
Longitudinal Phase Space Tomography with Space Charge
title Longitudinal Phase Space Tomography with Space Charge
title_full Longitudinal Phase Space Tomography with Space Charge
title_fullStr Longitudinal Phase Space Tomography with Space Charge
title_full_unstemmed Longitudinal Phase Space Tomography with Space Charge
title_short Longitudinal Phase Space Tomography with Space Charge
title_sort longitudinal phase space tomography with space charge
topic Accelerators and Storage Rings
url https://dx.doi.org/10.1103/PhysRevSTAB.3.124202
http://cds.cern.ch/record/468153
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AT koscielniakshanerupert longitudinalphasespacetomographywithspacecharge
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