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Wooldridge, E.

Paper Title Page
MOPC059 BBU Limitations for ERLs 199
 
  • E. Wooldridge, C. D. Beard, P. A. McIntosh, B. D. Muratori, S. L. Smith
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  
  The BBU threshold in ERLs is a limitation on the maximum beam current due to the interaction of the electron bunches and the Higher Order Modes (HOMs) contained within the RF cavities. Several factors are involved in determining the threshold current; from the cavity the Q, R/Q and degeneracy of the modes all play an important part. From the beam transport the values of the lattice functions α, β and μ have an effect. We will discuss the limits on these variables to provide a BBU current threshold greater than 100 mA for a multiple cavity machine and what will be required to provide higher currents. Also three different cavity profiles were investigated with the aim of reducing the BBU threshold. The TESLA 9-cell cavity was used as a baseline for comparison against possible 7-cell cavity designs, using the TESLA cell shape for their inner cells. The ends of the 7-cell cavities join to different sized beampipes, with radii of 39 mm and 54 mm, to allow the most of the HOMs to propagate to a broadband HOM absorber. Two different beampipe to cavity to transitions were investigated. The optimised 7-cell cavity will be shown to provide an increase in the BBU threshold.  
THPP002 EMMA RF Cavity Design and Prototype Testing at Daresbury 3374
 
  • C. D. Beard, P. A. Corlett, D. M. Dykes, P. Goudket, C. Hill, P. A. McIntosh, A. J. Moss, J. F. Orrett, J. H.P. Rogers, A. E. Wheelhouse, E. Wooldridge
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • N. Bliss
    STFC/DL, Daresbury, Warrington, Cheshire
  • A. E. Bogle, T. L. Grimm, A. A. Kolka
    Niowave, Inc., Lansing, Michigan
  
  At PAC’07 we discussed the design of a prototype cavity to be used on EMMA*. EMMA is a prototype non-scalling FFAG. It will contain 19 RF cavities operating at 1.3 GHz with a baseline accelerating voltage of 120 kV. A prototype cavity has been manufactured by Niowave, Inc. and we will present a discussion of its RF and mechanical design. This cavity was put through low power tests, to determine frequency, tuning range, shunt impedance and Q of the cavity; and high power tests, to confirm power handling ability, when it arrived at Daresbury Laboratory this spring. The results of these tests were compared to the simulations and a bead pull was carried out to obtain the field profile. The cavities for EMMA are likely to be powered by IOTs, these will be used for the high power tests, which will demonstrate cavity operation to the required maximum of 180 kV.

*E. Wooldridge et al. "RF Cavity Development for FFAG Application on ERLP at Daresbury," Proceedings of PAC’07, Albuquerque, NM (2007).

 
THPP004 EMMA - the World's First Non-scaling FFAG 3380
 
  • T. R. Edgecock
    STFC/RAL, Chilton, Didcot, Oxon
  • C. D. Beard, J. A. Clarke, C. Hill, S. P. Jamison, A. Kalinin, K. B. Marinov, N. Marks, P. A. McIntosh, B. D. Muratori, H. L. Owen, Y. M. Saveliev, B. J.A. Shepherd, R. J. Smith, S. L. Smith, S. I. Tzenov, E. Wooldridge
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • J. S. Berg, D. Trbojevic
    BNL, Upton, Long Island, New York
  • N. Bliss, C. J. White
    STFC/DL, Daresbury, Warrington, Cheshire
  • M. K. Craddock
    UBC & TRIUMF, Vancouver, British Columbia
  • J. L. Crisp, C. Johnstone
    Fermilab, Batavia, Illinois
  • Y. Giboudot
    Brunel University, Middlesex
  • E. Keil
    CERN, Geneva
  • D. J. Kelliher, S. Machida
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  • S. R. Koscielniak
    TRIUMF, Vancouver
  • F. Meot
    CEA, Gif-sur-Yvette
  • T. Yokoi
    OXFORDphysics, Oxford, Oxon
  
  EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. EMMA will be used to demonstrate the principle of this type of accelerator and study their features in detail. The design of the machine and its hardware components are now far advanced and construction is due for completion in summer 2009.