Paper  Title  Other Keywords  Page 

SUPB038  Multipole Field Effects for the Superconducting ParallelBar Deflecting/Crabbing Cavities  dipole, cavity, superconductivity, luminosity  92 


The superconducting parallelbar 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 parallelbar deflecting/crabbing cavity.  
MOPB016  Insitu Measurement of Beaminduced Fields in the Sband Accelerating Structures of the Diamond Light Source linac  linac, higherordermode, dipole, wakefield  204 


The Diamond preinjector linac uses two 5.2 m DESY linac IItype accelerating structures to generate a 100 MeV electron beam suitable for injection into the booster synchrotron. The structures are powered independently by two highpower Sband 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 highpower waveguide network. These modes are compared with an electromagnetic simulation of the structures. The negative impact of higherorder 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 HOMDamped Cavities  cavity, acceleration, HOM, linac  330 


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 HighVelocity Spoke Cavities  cavity, quadrupole, linac, simulation  345 


Multispokes superconducting cavities in the highbeta 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 offaxis are needed. We present a study of the multipoles expansion of the fields from an EM simulation field data for a twospoke cavity operating at 325 MHz, β = 0.82 and 500 MHz, β = 1.  
MOPB082  RF Parameters of the TE  Type Deflecting Structure for SBand Frequency Range  impedance, ion, linac, heavyion  366 


Funding: in part RBFR N 12020654a Effective compact deflecting structure* has been proposed for Lband frequency range preferably. RF parameters of this structure considered for Sband 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 Sixelectrode BPMs for Secondorder Moment Measurement  factory, electron, linac, storagering  464 


In the SPring8 linac, fourelectrode beam position monitors (BPMs) have been utilized for the measurement of the transverse firstorder moments, which correspond to the centroids of beam charge distributions. We have planed to measure the transverse secondorder moments of beams to obtain information of beam optics and its energy deviations during the topup beam injection without destruction of beams. Therefore, sixelectrode BPMs with circular and quasiellipse crosssections have been developed on the basis of a newly introduced theory. A lownoise signal processor for the sixelectrode 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 sixelectrode BPM with circular crosssection and the old signal processor. The measured sensitivities and resolutions of the secondorder moments showed good agreement with the theory.  
Slides TUPLB09 [8.248 MB]  
TUPB058  An Analytical Cavity Model for Fast LinacBeam Tuning  quadrupole, cavity, dipole, simulation  609 


Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DESC0000661 Nonaxisymmetric RF cavities can produce axially asymmetric acceleration fields. Conventional method using numerical 3D field tracking to address this feature is timeconsuming and thus not appropriate for online beam tuning applications. In this paper, we develop analytical treatment of nonaxisymmetric RF cavities. Multipole models of cavities are derived using realistic 3D field in both longitudinal and transverse dimensions. Then, beam dynamics formulism is established. Finally, special case of FRIB quarterwave resonators are calculated by the model and benchmarked against 3D field tracking to ensure the efficiency and accuracy of the model. 

TUPB079  Design and Beam Test of SixElectrode BPMs for SecondOrder Moment Measurement  factory, electron, linac, storagering  654 


In the SPring8 linac, fourelectrode beam position monitors (BPMs) have been utilized for the measurement of the transverse firstorder moments, which correspond to the centroids of beam charge distributions. We have planed to measure the transverse secondorder moments of beams to obtain information of beam optics and its energy deviations during the topup beam injection without destruction of beams. Therefore, sixelectrode BPMs with circular and quasiellipse crosssections have been developed on the basis of a newly introduced theory. A lownoise signal processor for the sixelectrode 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 sixelectrode BPM with circular crosssection and the old signal processor. The measured sensitivities and resolutions of the secondorder moments showed good agreement with the theory.  
THPB062  Multipole Field Effects for the Superconducting ParallelBar/RFDipole Deflecting/Crabbing Cavities  dipole, cavity, superconductivity, luminosity  981 


The superconducting parallelbar 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 parallelbar deflecting/crabbing cavity.  