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Tuckmantel, J.

Paper Title Page
FRPMN069 Longitudinal Coupled-Bunch Instabilities in the CERN PS 4180
  • H. Damerau, S. Hancock, C. Rossi, E. N. Shaposhnikova, J. Tuckmantel, J.-L. Vallet
    CERN, Geneva
  • M. Mehler
    GSI, Darmstadt
  Funding: Work supported by EU Design Study DIRACsecondary-Beams (contract 515873).

Longitudinal coupled bunch instabilities in the CERN PS represent a major limitation to the high brightness beam delivered for the LHC. To identify possible impedance sources for these instabilities, machine development studies have been carried out. The growth rates of coupled bunch modes have been measured, and modes have been identified using mountain range data. Growth rate estimations from coupled bunch mode theory are compared to these results. It is shown that the longitudinal impedance of the broad resonance curve of the main 10 MHz RF system can be identified as the most probable source. Possible methods to improve the beam stability are analyzed together with the performance of a damping system.

FRPMN070 Controlled Longitudinal Emittance Blow-up in the CERN PS 4186
  • H. Damerau, M. Morvillo, E. N. Shaposhnikova, J. Tuckmantel, J.-L. Vallet
    CERN, Geneva
  The longitudinal emittance of the bunches in the CERN PS must be increased before transition crossing to avoid beam loss due to a fast vertical instability. This controlled blow-up is essential for all high-intensity beams in the PS, including those for transfer to the LHC. The higher harmonic 200 MHz RF system (six cavities) used for this blow-up has to generate a total RF voltage which, for the most demanding blow-up, is comparable to the voltage of the main RF cavities. The system is presently subject to a major upgrade and a possible reduction in the number of higher harmonic RF cavities installed is under consideration. To determine the minimum required, detailed simulations and machine development studies to optimize the longitudinal blow-up have been performed. Further options to produce the required longitudinal emittance using other RF systems are also analyzed. The results obtained for the different scenarios for the longitudinal blow-up are presented and compared in this paper.