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Bruns, W.

Paper Title Page
MOPP050 Electron Cloud Build Up and Instability in the CLIC Damping Rings 661
 
  • G. Rumolo, Y. Papaphilippou
    CERN, Geneva
  • W. Bruns
    WBFB, Berlin
 
  Electron cloud can be formed in the CLIC positron damping ring and cause intolerable tune shift and beam instability. 2D and 3D build up simulations with the Faktor2 code, developed at CERN, have been done to predict the cloud formation in the arcs and wigglers of the damping rings. HEADTAIL simulations have been used to study the effect of this electron cloud on the beam and assess the thresholds above which the electron cloud instability would set in.  
MOPP057 ILC DR Vacuum Design and E-cloud 673
 
  • O. B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • W. Bruns
    WBFB, Berlin
 
  An electron cloud parameters and vacuum design are tightly bounded to each other. Input parameters for the e-cloud depend on shape of vacuum chamber and surface property (material, roughthness, coatings, etc.), electron multipacting in the vacuum chamber causes the electron stimulated gas desorption and may require modification of vacuum system to deal with it. This paper describes the e-cloud modelling performed in a way to optimise ILC DR vacuum design in positron ring and to have clear understanding what modification in vacuum chamber are required. Three parameters of e-cloud were varied in turn: photo-electron emission, secondary electron yield and gas pressure. It was found all three parameter should not exceed certain value to keep the e-cloud density to an acceptable level. The energy and intensity of electron bombardment of the vacuum chamber walls and electron stimulated gas desorption were also calculated. It was found that electron stimulated gas desorption is comparable or larger than the photon stimulated desorption and should be considered in vacuum design.  
TUPP087 Short Range Wakepotentials Computed in a Moving Frame 1733
 
  • W. Bruns
    WBFB, Berlin
 
  When computing wakepotentials in a frame moving in the same direction as the exciting charge, the relativistic charge is stretched by the factor gamma of the frame's velocity. Because the needed mesh density is proportional to the length of the charge, the moving frame allows a larger gridspacing. The paper presents some implementation details of the handling of the material boundaries moving though the computational volume, and reports some results.