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Dexter, A.C.

Paper Title Page
MOPLS075 Progress towards Crab Cavity Solutions for the ILC 724
 
  • G. Burt, A.C. Dexter
    Cockcroft Institute, Warrington, Cheshire
  • C.D. Beard, P. Goudket
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • L. Bellantoni
    Fermilab, Batavia, Illinois
 
  In order to achieve acceptable luminosity for ILC crossing angles greater than a few mrad, RF deflection cavities must be used to rotate electron and position bunches leading up to the IP. A bunch that passes through a deflection cavity at a phase where the deflection averages to zero receives a crab kick leading to a finite rotation at the IP. For a beam energy of 500GeV and a crossing angle of 20mrad, the required crab kick is about 19.5MV at 1.3GHz and 6.5MV at 3.9GHz. Cavities are needed on both beams and are likely to be positioned about 12m before the IP. Any RF phase error between the bunch and the cavity leads to a deflection of the bunch in addition to a rotation of the bunch. Any differential phase error between the cavities leads to differing deflections and consequential loss in luminosity. Collaborative work with FNAL, being undertaken to develop a variant of their 3.9GHz CKM cavity optimised for an ILC solution, is described. Current analysis favours a solution with four nine-cell cavities on each beam. It is anticipated that the cavities will be run CW and driven from small Klystron/s (< 5kW) or solid state amplifiers.*

*We would like to thank Chris Adolphsen, SLAC, for his help in technical discussions, which were greatly appreciated.

 
MOPCH163 Analysis of Wakefields in the ILC Crab Cavity 442
 
  • G. Burt, A.C. Dexter
    Microwave Research Group, Lancaster University, Lancaster
  • C.D. Beard, P. Goudket
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • L. Bellantoni
    Fermilab, Batavia, Illinois
  • R.M. Jones
    UMAN, Manchester
 
  The large crossing angle schemes of the ILC need a correction of bunch orientation at the IP in order to recover a luminosity loss of up to 80%. The orientation of bunches can be changed using a transverse deflecting cavity. The location of the crab cavity would be close to the final focus, and small deflections caused by wakefields in the cavities could cause misalignments of the bunches at the IP. Wakefields in the FNAL CKM cavities have been analysed and their effects studied in view of use as the ILC crab cavity. Numerical simulations have been performed to analyse the transverse wakepotentials of up to quadrupole order modes in this cavity and the effect upon bunches passing through this cavity. Trapped modes within the CKM cavity have been investigated. Perturbation tests of normal conducting models of this cavity have been launched to verify these results. The effect of the final focus quadrupole magnets on the deflection given to the bunch have also been calculated and used to calculate luminosity loss due to wakefields.