Author: Hall, B.D.S.
Paper Title Page
WEPPC032 Analysis of the Four Rod Crab Cavity for HL-LHC 2275
  • B.D.S. Hall, P.K. Ambattu, G. Burt, D. Doherty, C. Lingwood
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • P. Goudket
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  The Hi-Lumi Upgrade to the LHC will utilise crab cavities to increase the peak luminosity and provide luminosity levelling at the increased crossing angle. A transversely compact design is required to fit within the limited space between opposing beamlines. In this paper a four rod TEM deflecting cavity (4RCC) is shown to be suitable for LHC. The variation of the deflecting voltage with radial offset has been minimised by careful design and an aluminium prototype has been constructed and beadpull measurements are compared to simulations. Multipacting simulations have been performed on the cavity geometry and it is predicted that the growth rate is less than unity for a clean surface. Pressure variations in the LHe can result in deformation of the complex shape which will alter the resonant frequency. Mechanical simulations have also been performed to assess the sensitivity of the frequency to pressure. In order to reduce the impact of these cavities on the LHC beam low impedance is required for the HOMs as well as the fundamental monopole mode. The couplers for the 4RCC cavity have been optimised to provide effective damping of these modes while rejecting the operating mode.