uu.seUppsala University Publications
Change search
Refine search result
1 - 19 of 19
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings2014In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 50, no 9, article id 8101809Article in journal (Refereed)
    Abstract [en]

    Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.

  • 2.
    Ali, Hasan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Eriksson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Li, Hu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, S. Hassan M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar, M. S. Sharath
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    An electron energy loss spectrometer based streak camera for time resolved TEM measurements2017In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 176, p. 5-10Article in journal (Refereed)
    Abstract [en]

    We propose an experimental setup based on a streak camera approach inside an energy filter to measure time resolved properties of materials in the transmission electron microscope (TEM). In order to put in place the streak camera, a beam sweeper was built inside an energy filter. After exciting the TEM sample, the beam is swept across the CCD camera of the filter. We describe different parts of the setup at the example of a magnetic measurement. This setup is capable to acquire time resolved diffraction patterns, electron energy loss spectra (EELS) and images with total streaking times in the range between 100 ns and 10 μs.

  • 3.
    Bhattacharyya, Anirban
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Holz, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Wave propagation in a fractal wave guide2017In: in Proceedings of the 8th International Particle Accelerator Conference (IPAC 2017), Copenhagen, Denmark, May, 2017., 2017Conference paper (Other academic)
  • 4.
    Borgmann, Ch.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Jacewicz, Marek
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Olvegård, Maja
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    The Momentum Distribution Of The Decelerated Drive Beam In Clic And The Two-Beam Test Stand At Ctf32014In: Proceedings of IPAC2014, Dresden, Germany., 2014, p. 62-64Conference paper (Other academic)
  • 5. Farabolini, W.
    et al.
    Peauger, F.
    Borgmann, C.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ruber, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Corsini, R.
    Gamba, D.
    Grudiev, A.
    Khan, M. A.
    Mazzoni, S.
    Quirante, J. L. Navarro
    Pan, R.
    Towler, J.
    Vitoratou, N.
    Yaqub, K.
    Recent Results from CTF3 Two Beam Test Stand2014In: Proceedings, 5th International Particle Accelerator Conference (IPAC 2014): Dresden, Germany, June 15-20, 2014, 2014Conference paper (Other academic)
  • 6.
    Hamberg, Mathias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Vargas Catalan, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Dancila, Dragos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Jacewicz, Marek
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Kuittinen, M.
    Institute of Photonics, University of Eastern Finland, Finland.
    Vartiainen, I.
    Institute of Photonics, University of Eastern Finland, Finland.
    Dielectric Laser Acceleration Setup Design, Grating Manufacturing and Investigations Into Laser Induced RF Cavity Breakdowns2017In: Proceedings of FEL2017, Santa Fe, NM, USA, 2017Conference paper (Refereed)
  • 7.
    Hamberg, Mathias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Vargas Catalan, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Jacewicz, Marek
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Dielectric laser accelerator investigation, setup substrate manufacturing and investigation of effects of laser induced electromigration rf cavity breakdown influences2017In: Proceedings of the 8th International Particle Accelerator Conference (IPAC 2017), Copenhagen, Denmark, May, 2017, 2017Conference paper (Refereed)
  • 8.
    Jacewicz, Marek
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Borgmann, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ögren, Jim
    Olvegård, Maja
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    General-purpose spectrometer for vacuum breakdown diagnostics for the 12 GHz test stand at CERN2014Conference paper (Other academic)
  • 9. Quirante, J. L. Navarro
    et al.
    Corsini, R.
    Grudiev, A.
    Lefevre, T.
    Mazzoni, S.
    Pan, R.
    Tecker, F.
    Farabolini, W.
    Peuger, F.
    Gamba, D.
    Yaqub, K.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Vitoratou, N.
    CALIFES: A Multi-Purpose Electron Beam for Accelerator Technology Tests2014In: Proceedings, 27th Linear Accelerator Conference, LINAC2014: Geneva, Switzerland, August 31-September 5, 2014, 2014Conference paper (Other academic)
  • 10.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Beam Diagnostics and Dynamics in Nonlinear Fields2017Doctoral 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.

    List of papers
    1. Measuring the full transverse beam matrix using a single octupole
    Open this publication in new window or tab >>Measuring the full transverse beam matrix using a single octupole
    2015 (English)In: Physical Review Special Topics. Accelerators and Beams, ISSN 1098-4402, E-ISSN 1098-4402, Vol. 18, no 7, article id 072801Article in journal (Refereed) Published
    Abstract [en]

    We propose a method to fully determine the transverse beam matrix using a simple setup consisting of two steering magnets, an octupole field and a screen. This works in principle for any multipole field, i.e., sextupole, octupole magnet or a radio frequency structure with a multipole field. We have experimentally verified the method at the Compact Linear Collider Test Facility 3 at CERN using a Compact Linear Collider accelerating structure, which has an octupole component of the radio frequency fields. By observing the position shifts of the beam centroid together with changes in transverse beam size on a screen, we determined the full transverse beam matrix, with all correlations.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-259088 (URN)10.1103/PhysRevSTAB.18.072801 (DOI)000357647600001 ()
    Funder
    Knut and Alice Wallenberg FoundationSwedish Research Council, 2011-6305, 2014-6360
    Available from: 2015-07-29 Created: 2015-07-27 Last updated: 2017-12-04Bibliographically approved
    2. Aligning linac accelerating structures using a copropagating octupolar mode
    Open this publication in new window or tab >>Aligning linac accelerating structures using a copropagating octupolar mode
    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
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-331616 (URN)10.1103/PhysRevAccelBeams.20.102801 (DOI)000413054500001 ()
    Funder
    Knut and Alice Wallenberg FoundationSwedish Research Council, 2011-6305Swedish Research Council, 2014-6360
    Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2018-01-29Bibliographically approved
    3. Beam-based alignment studies at CTF3 using the octupole component of CLIC accelerating structures
    Open this publication in new window or tab >>Beam-based alignment studies at CTF3 using the octupole component of CLIC accelerating structures
    Show others...
    2017 (English)In: in Proceedings of the 8th International Particle Accelerator Conference (IPAC 2017), Copenhagen, Denmark, May, 2017., 2017Conference paper, Published paper (Other academic)
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-329988 (URN)978-3-95450-182-3 (ISBN)
    Conference
    IPAC 2017
    Available from: 2017-09-25 Created: 2017-09-25 Last updated: 2017-10-19
    4. Compensating amplitude-dependent tune-shift without driving fourth-order resonances
    Open this publication in new window or tab >>Compensating amplitude-dependent tune-shift without driving fourth-order resonances
    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, p. 1-9Article 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.

    Keywords
    Beam dynamics, Nonlinear beam dynamics
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-329979 (URN)10.1016/j.nima.2017.06.047 (DOI)000409530200001 ()
    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
    5. Optimum resonance control knobs for sextupoles
    Open this publication in new window or tab >>Optimum resonance control knobs for sextupoles
    2018 (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. 894, p. 111-118Article in journal (Refereed) Published
    Abstract [en]

    We discuss the placement of extra sextupoles in a magnet lattice that allows to correct third-order geometric resonances, driven by the chromaticity-compensating sextupoles, in a way that requires the least excitation of the correction sextupoles. We consider a simplified case, without momentum-dependent effects or other imperfections, where suitably chosen phase advances between the correction sextupoles leads to orthogonal knobs with equal treatment of the different resonance driving terms.

    National Category
    Accelerator Physics and Instrumentation
    Identifiers
    urn:nbn:se:uu:diva-330972 (URN)10.1016/j.nima.2018.03.041 (DOI)000430704600014 ()
    Funder
    Swedish Research Council, 2011-6305Swedish Research Council, 2014-6360Knut and Alice Wallenberg Foundation
    Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2018-08-03Bibliographically approved
    6. Surface Characterization and Field Emission Measurements of Copper Samples inside a Scanning Electron Microscope
    Open this publication in new window or tab >>Surface Characterization and Field Emission Measurements of Copper Samples inside a Scanning Electron Microscope
    2016 (English)Conference paper, Published paper (Other academic)
    Abstract [en]

    Vacuum breakdown in normal-conducting accelerating structures is a limiting factor for high gradient acceleration.Many aspects of the physics governing the breakdown process and its onset are yet to be fully understood. At Uppsala University we address these questions with an in-situ experi-mental setup mounted in an environmental scanning electron microscope. It consists of a piezo motor driven tungsten needle and a sample surface mounted on a piezo stage, allowing for nano-meter 3D-position control. One of the piezomotors controls the needle-sample gap while the two otherscan across the surface. A DC-voltage up to 1 kV is  applied across the gap and field emission currents from a coppersurface are measured with an electrometer. Here we presentthe setup and some initial results.

    National Category
    Accelerator Physics and Instrumentation Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-298811 (URN)
    Conference
    the 7th International Particle Accelerator Conference IPAC16 in Busan, South Korea, May 2016
    Available from: 2016-07-08 Created: 2016-07-08 Last updated: 2017-10-19Bibliographically approved
  • 11.
    Ögren, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    ELEPHANT: A MATLAB-code for Hamiltonians, Lie algebra, normal form and particle tracking2017Report (Other academic)
    Abstract [en]

    In this report we explain the structure and functionality of ELEPHANT: a MATLAB-code developed for particle tracking and treating Hamiltonians in the Lie formalism with applications for accelerator physics. The code can operate on Hamiltonians and using the similarity transform and the Campbell-Baker-Hausdorff formula to express a map as an effective Hamiltonian and a linear map.The code can also express a map in a normal form and from this calculate the amplitude-dependenttune-shifts. Finally, the code can analyze the standard linear transverse dynamics and do particletracking. The purpose of the code is to treat nonlinear fields analytically and cross-check with tracking results.

  • 12.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Bhattacharyya, Anirban
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Holz, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Farabolini, W.
    Beam-based alignment studies at CTF3 using the octupole component of CLIC accelerating structures2017In: in Proceedings of the 8th International Particle Accelerator Conference (IPAC 2017), Copenhagen, Denmark, May, 2017., 2017Conference paper (Other academic)
  • 13.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Jafri, Hassan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Surface Characterization and Field Emission Measurements of Copper Samples inside a Scanning Electron Microscope2016Conference paper (Other academic)
    Abstract [en]

    Vacuum breakdown in normal-conducting accelerating structures is a limiting factor for high gradient acceleration.Many aspects of the physics governing the breakdown process and its onset are yet to be fully understood. At Uppsala University we address these questions with an in-situ experi-mental setup mounted in an environmental scanning electron microscope. It consists of a piezo motor driven tungsten needle and a sample surface mounted on a piezo stage, allowing for nano-meter 3D-position control. One of the piezomotors controls the needle-sample gap while the two otherscan across the surface. A DC-voltage up to 1 kV is  applied across the gap and field emission currents from a coppersurface are measured with an electrometer. Here we presentthe setup and some initial results.

  • 14.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Farabolini, W.
    CERN, CH-1211 Geneva 23, Switzerland; CEA, IRFU, Ctr Etud Saclay, F-91191 Gif Sur Yvette, France.
    Measuring the full transverse beam matrix using a single octupole2015In: Physical Review Special Topics. Accelerators and Beams, ISSN 1098-4402, E-ISSN 1098-4402, Vol. 18, no 7, article id 072801Article in journal (Refereed)
    Abstract [en]

    We propose a method to fully determine the transverse beam matrix using a simple setup consisting of two steering magnets, an octupole field and a screen. This works in principle for any multipole field, i.e., sextupole, octupole magnet or a radio frequency structure with a multipole field. We have experimentally verified the method at the Compact Linear Collider Test Facility 3 at CERN using a Compact Linear Collider accelerating structure, which has an octupole component of the radio frequency fields. By observing the position shifts of the beam centroid together with changes in transverse beam size on a screen, we determined the full transverse beam matrix, with all correlations.

  • 15.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    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.
    Aligning linac accelerating structures using a copropagating octupolar mode2017In: Physical Review Accelerators and Beams, ISSN 2469-9888, Vol. 20, article id 102801Article in journal (Refereed)
    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.

  • 16.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Beam-based Alignment of CLIC Accelerating Structures Utilizing Their Octupole Component2016Conference paper (Other academic)
    Abstract [en]

    Alignment of the accelerating structures is essential foremittance preservation in long linear accelerators such as the Compact Linear Collider (CLIC). The prototype structures for CLIC have four radial waveguides connected to each cellfor damping wakefields and this four-fold symmetry is re-sponsible for an octupole component of the radio-frequency fields, phase-shifted 90 degrees with respect to the accelerating mode. The octupole field causes a nonlinear dependence of the transverse beam deflection with respect to the position within the accelerating structure. By transversely moving the beam with two upstream steering magnets, and observing the deflection with beam position monitors or screens, the electromagnetic center of the structure can be found. Wediscuss the applicability of this method for aligning the beamin the accelerating structures.

  • 17.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Compensating amplitude-dependent tune-shift without driving fourth-order resonances2017In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 869, p. 1-9Article in journal (Refereed)
    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.

  • 18.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Optimum resonance control knobs for sextupoles2018In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 894, p. 111-118Article in journal (Refereed)
    Abstract [en]

    We discuss the placement of extra sextupoles in a magnet lattice that allows to correct third-order geometric resonances, driven by the chromaticity-compensating sextupoles, in a way that requires the least excitation of the correction sextupoles. We consider a simplified case, without momentum-dependent effects or other imperfections, where suitably chosen phase advances between the correction sextupoles leads to orthogonal knobs with equal treatment of the different resonance driving terms.

  • 19.
    Ögren, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ziemann, Volker
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Farabolini, W.
    A method for determining the roll angle of the CLIC accelerating structures from the beam shape downstream of the structure2017In: in Proceedings of the 8th International Particle Accelerator Conference (IPAC 2017), Copenhagen, Denmark, May, 2017., 2017Conference paper (Other academic)
1 - 19 of 19
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf