Author: Verdu-Andres, S.     [Verdú-Andrés, S.]
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MOPMF020 Higher Order Mode Coupling Options for the eRHIC Crab Cavity 121
 
  • Q. Wu, I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: This work was supported by the US Department of Energy via Brookhaven Science Associates LLC under contract no. DE-SC0012704.
The eRHIC crab cavity adopts the double quarter wave structure developed at Brookhaven National Lab for the LHC Hi-Lumi upgrade crab cavities. The cavity's fundamental mode is at 338 MHz with the first higher order mode more than 180 MHz above that. We looked into the higher order mode distribution up to 2 GHz, and considered various locations and geometries of the coupling scheme. The cylindrical outer shell of the cavity allowed various possibilities for coupler port openings on all the walls, which were difficult for the narrow waist of the LHC double quarter wave crab cavities. Beam pipe absorbers are also options for simpler high frequency modes damping. Some preliminary high pass filter design will also be discussed in this paper. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF020  
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WEPMF012 Power Requirement and Preliminary Coupler Design for the eRHIC Crab Cavity System 2394
 
  • S. Verdú-Andrés, I. Ben-Zvi, D. Holmes, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: Work supported by Brookhaven Science Associates LLC under contract no. DE-SC0012704 with the U.S. Department of Energy.
Crab cavities are deflecting cavities operated in such a way that the bunch center is in synchronism with the zero-crossing kick voltage. In that case, beam loading is zero for an on-axis beam. The crab cavity system of the future electron-ion collider eRHIC will manipulate 275 GeV proton beams. At high energies, the beam offset can be as large as 2 mm (including mechanical and electrical offset tolerances). The beam loading resulting from such offset can greatly incur in large power requirements to the RF amplifier. The choice of external Q for the Fundamental Power Coupler (FPC) is critical to limit the power requirement to practical values. The loaded Q of the eRHIC crab cavities is mainly governed by the external Q of the FPC, so the external Q will also define the cavity bandwidth and thus the tuning requirements to counteract frequency transients from external perturbations. This paper discusses the choice of external Q for the FPC of the eRHIC crab cavities and introduces the design of a preliminary FPC antenna concept that would provide the appropriate external Q. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF012  
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THPAL018 DQW HOM Coupler Design for the HL-LHC 3663
 
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R. Calaga
    CERN, Geneva, Switzerland
  • S. Verdú-Andrés, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  HOMs in the DQW crab cavity can produce large heat loads and beam instabilities as a result of the high current HL-LHC beams. The DQW crab cavity has on-cavity, coaxial HOM couplers to damp the HOMs whilst providing a stop-band response to the fundamental mode. Manufacturing experience and further simulations give rise to a set of desirable coupler improvements. This paper will assess the performance of the current HOM coupler design, present operational improvements and propose an evolved design for HL-LHC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL018  
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