Keyword: HOM
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TUPG12 Design for the Diamond Longitudinal Bunch-by-Bunch Feedback Cavity cavity, impedance, resonance, coupling 340
  • A.F.D. Morgan, G. Rehm
    DLS, Oxfordshire, United Kingdom
  In 2017 it is planned to install some additional normal conducting cavities into the Diamond storage ring. In order to deal with the potential higher order modes in these we are designing a longitudinal bunch-by-bunch feedback system. This paper will focus on the design of the overloaded cavity kicker, adapted to the Diamond beam pipe cross section. The design has evolved in order to reduce the strong 3rd harmonic resonance seen on the introduction of the racetrack beam pipe. Through a combination of geometry optimisation and the addition of integrated taper transitions this harmonic has been greatly reduced while also minimising sharp resonances below 15GHz. The major features will be described, as well as the expected performance parameters.  
poster icon Poster TUPG12 [1.423 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG12  
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WEPG03 HOM Characterization for Beam Diagnostics at the European XFEL Injector cavity, dipole, monitoring, electron 616
  • N. Baboi, T. Hellert, L. Shi, T. Wamsat
    DESY, Hamburg, Germany
  • R.M. Jones, N.Y. Joshi, L. Shi
    UMAN, Manchester, United Kingdom
  • N.Y. Joshi
    University of Manchester, Manchester, United Kingdom
  Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 31245.
Higher Order Modes (HOM) excited by bunched elec-tron beams in accelerating cavities carry information about the beam position and phase. This principle is used at the FLASH facility, at DESY, for beam position monitoring in 1.3 and 3.9 GHz cavities. Dipole modes, which depend on the beam offset, are used. Similar monitors are now under design for the European XFEL. In addition to beam position, the beam phase with respect to the accelerating RF will be monitored using monopole modes from the first higher order monopole band. The HOM signals are available from two couplers installed on each cavity. Their monitoring will allow the on-line tracking of the phase stability over time, and we anticipate that it will improve the stability of the facility. As part of the monitor designing, the HOM spectra in the cavities of the 1.3 and 3.9 GHz cryo-modules installed in the European XFEL injector have been measured. This paper will present their dependence on the beam position. The variation in the modal distribution from cavity to cavity will be discussed. Based on the results, initial phase measurements based on a fast oscilloscope have been made.
poster icon Poster WEPG03 [3.281 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG03  
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