Keyword: multipole
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SUPB038 Multipole Field Effects for the Superconducting Parallel-Bar Deflecting/Crabbing Cavities dipole, cavity, superconductivity, luminosity 92
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
 
  The superconducting parallel-bar deflecting/crabbing cavity is currently being considered as one of the design options in rf separation for the Jefferson Lab 12 GeV upgrade and for the crabbing cavity for the proposed LHC luminosity upgrade. Knowledge of multipole field effects is important for accurate beam dynamics study of rf structures. The multipole components can be accurately determined numerically using the electromagnetic surface field data in the rf structure. This paper discusses the detailed analysis of those components for the fundamental deflecting/crabbing mode and higher order modes in the parallel-bar deflecting/crabbing cavity.  
 
MOPB016 In-situ Measurement of Beam-induced Fields in the S-band Accelerating Structures of the Diamond Light Source linac linac, higher-order-mode, dipole, wakefield 204
 
  • C. Christou
    Diamond, Oxfordshire, United Kingdom
 
  The Diamond pre-injector linac uses two 5.2 m DESY linac II-type accelerating structures to generate a 100 MeV electron beam suitable for injection into the booster synchrotron. The structures are powered independently by two high-power S-band klystrons and are designed to operate at 3 GHz. Higher order modes up to 14 GHz induced by beam in unpowered accelerating and bunching structures have been directly measured using directional couplers in the high-power waveguide network. These modes are compared with an electromagnetic simulation of the structures. The negative impact of higher-order wakes on the bunch trains used at Diamond is considered, and the use of the multipole field measurement for alignment of the beam to the structure is investigated.  
 
MOPB066 Alternative Approaches for HOM-Damped Cavities cavity, acceleration, HOM, linac 330
 
  • B. Riemann, T. Weis
    DELTA, Dortmund, Germany
  • A. Neumann
    HZB, Berlin, Germany
 
  Funding: this work is partly funded by BMBF contract no. 05K10PEA
Elliptical cavities have been a standard in SRF linac technology for 30 years. We present another approach to base cell geometry based on Bezier splines, that leads to equal performance levels and is much more flexible in terms of optimization. Using the BERLinPro main linac as an example, a spline multicell cavity is designed with equal performance goals. For the damping of higher order modes (HOMs), the installation of waveguides at the ends of a multicell cavity is a common approach.
 
 
MOPB072 Multipole Expansion of the Fields in Superconducting High-Velocity Spoke Cavities cavity, quadrupole, linac, simulation 345
 
  • R.G. Olave, J.R. Delayen, C.S. Hopper
    ODU, Norfolk, Virginia, USA
 
  Multi-spokes superconducting cavities in the high-beta regime are being considered for a number of applications. In order to accurately model the dynamics of the particles in such cavities, knowledge of the fields off-axis are needed. We present a study of the multipoles expansion of the fields from an EM simulation field data for a two-spoke cavity operating at 325 MHz, β = 0.82 and 500 MHz, β = 1.  
 
MOPB082 RF Parameters of the TE - Type Deflecting Structure for S-Band Frequency Range impedance, ion, linac, heavy-ion 366
 
  • V.V. Paramonov, L.V. Kravchuk
    RAS/INR, Moscow, Russia
  • K. Flöttmann
    DESY, Hamburg, Germany
 
  Funding: in part RBFR N 12-02-0654-a
Effective compact deflecting structure* has been proposed for L-band frequency range preferably. RF parameters of this structure considered for S-band frequency range both for traveling and standing wave operation.
* -V. Paramonov, L. Kravchuk, INR, S. Korepanov. Effective Standing Wave RF Structure for Particle Beam Deflector. Proc. 2006 Linac Conference, p. 649
 
 
TUPLB09 Design and Beam Test of Six-electrode BPMs for Second-order Moment Measurement factory, electron, linac, storage-ring 464
 
  • K. Yanagida, H. Hanaki, S. Suzuki
    JASRI/SPring-8, Hyogo-ken, Japan
 
  In the SPring-8 linac, four-electrode beam position monitors (BPMs) have been utilized for the measurement of the transverse first-order moments, which correspond to the centroids of beam charge distributions. We have planed to measure the transverse second-order moments of beams to obtain information of beam optics and its energy deviations during the top-up beam injection without destruction of beams. Therefore, six-electrode BPMs with circular and quasi-ellipse cross-sections have been developed on the basis of a newly introduced theory. A low-noise signal processor for the six-electrode BPM has also been developed to perform fine measurement. We expected the following resolutions determined by the S/N ratio of the circuit; the first order moments (beam positions) > 1 μm, and the second order moments with a size > 110 μm. The first beam test was carried out using the six-electrode BPM with circular cross-section and the old signal processor. The measured sensitivities and resolutions of the second-order moments showed good agreement with the theory.  
slides icon Slides TUPLB09 [8.248 MB]  
 
TUPB058 An Analytical Cavity Model for Fast Linac-Beam Tuning quadrupole, cavity, dipole, simulation 609
 
  • Z.Q. He, Z. Zheng
    TUB, Beijing, People's Republic of China
  • Z.Q. He, Z. Liu, J. Wei, Y. Zhang
    FRIB, East Lansing, Michigan, USA
 
  Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Non-axisymmetric RF cavities can produce axially asymmetric acceleration fields. Conventional method using numerical 3-D field tracking to address this feature is time-consuming and thus not appropriate for on-line beam tuning applications. In this paper, we develop analytical treatment of non-axisymmetric RF cavities. Multipole models of cavities are derived using realistic 3-D field in both longitudinal and transverse dimensions. Then, beam dynamics formulism is established. Finally, special case of FRIB quarter-wave resonators are calculated by the model and benchmarked against 3-D field tracking to ensure the efficiency and accuracy of the model.
 
 
TUPB079 Design and Beam Test of Six-Electrode BPMs for Second-Order Moment Measurement factory, electron, linac, storage-ring 654
 
  • K. Yanagida, H. Hanaki, S. Suzuki
    JASRI/SPring-8, Hyogo-ken, Japan
 
  In the SPring-8 linac, four-electrode beam position monitors (BPMs) have been utilized for the measurement of the transverse first-order moments, which correspond to the centroids of beam charge distributions. We have planed to measure the transverse second-order moments of beams to obtain information of beam optics and its energy deviations during the top-up beam injection without destruction of beams. Therefore, six-electrode BPMs with circular and quasi-ellipse cross-sections have been developed on the basis of a newly introduced theory. A low-noise signal processor for the six-electrode BPM has also been developed to perform fine measurement. We expected the following resolutions determined by the S/N ratio of the circuit; the first order moments (beam positions) >1 μm, and the second order moments with a size >110 μm. The first beam test was carried out using the six-electrode BPM with circular cross-section and the old signal processor. The measured sensitivities and resolutions of the second-order moments showed good agreement with the theory.  
 
THPB062 Multipole Field Effects for the Superconducting Parallel-Bar/RF-Dipole Deflecting/Crabbing Cavities dipole, cavity, superconductivity, luminosity 981
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
 
  The superconducting parallel-bar deflecting/crabbing cavity is currently being considered as one of the design options in rf separation for the Jefferson Lab 12 GeV upgrade and for the crabbing cavity for the proposed LHC luminosity upgrade. Knowledge of multipole field effects is important for accurate beam dynamics study of rf structures. The multipole components can be accurately determined numerically using the electromagnetic surface field data in the rf structure. This paper discusses the detailed analysis of those components for the fundamental deflecting/crabbing mode and higher order modes in the parallel-bar deflecting/crabbing cavity.