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Weathersby, S.P.

Paper Title Page
TPPP030 Damping Higher Order Modes in the PEP-II B-Factory Vertex Bellows 2131
 
  • S.P. Weathersby, J. Langton, A. Novokhatski, J. Seeman
    SLAC, Menlo Park, California
 
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC03-76SF00515.

Higher stored currents and shorter bunch lengths are requirements for increasing luminosity in colliding storage rings. As a result, more HOM power is generated in the IP region. This HOM power propagates to sensitive components causing undesirable heating, thus becoming a limiting issue for the PEP-II B-factory. HOM field penetration through RF shielding fingers has been shown to cause heating in bellows structures. To overcome these limitations, a proposal to incorporate ceramic absorbers within the bellows cavity to damp these modes is presented. Results show that the majority of modes of interest are damped, the effectiveness depending on geometrical considerations. An optimal configuration is presented for the PEP-II B-factory IR bellows component utilizing commercial grade ceramics with consideration for heat transfer requirements.

 
TPPP031 A Proposal for a New HOM Absorber in a Straight Section of the PEP-II Low Energy Ring 2173
 
  • S.P. Weathersby, M. Kosovsky, N. Kurita, A. Novokhatski, J. Seeman
    SLAC, Menlo Park, California
 
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC03-76SF00515.

Attainment of high luminosity in storage ring colliders necessitates increasing stored currents and reducing bunch lengths. Consequently, intense beam fields will scatter more power into higher order modes from beam line sources such as collimators, masks and tapers. This power penetrates into sensitive components such as a bellows, causing undesirable heating and limits machine performance. To overcome this limitation we propose incorporating ceramic absorbers in the vicinity of the bellows to damp beam induced modes while preserving a matched impedance to the beam. This is accomplished with an absorber configuration which damps TE dipole and quadrupole traveling waves while preserving TM monopole propagation. A scattering parameter analysis is presented utilizing properties of commercial grade ceramics and indicates a feasible solution.