| Paper |
Title |
Page |
| TUPP059 |
Study of Controlled Longitudinal Emittance Blow-up for High Intensity LHC Beams in the CERN SPS
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1676 |
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- G. Papotti, T. Bohl, T. P.R. Linnecar, E. N. Shaposhnikova, J. Tuckmantel
CERN, Geneva
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Preventive longitudinal emittance blow-up, in addition to a fourth harmonic Landau damping RF system, is required to keep the LHC beam in the SPS stable up to extraction. The beam is blown-up in a controlled way during the acceleration ramp by using band-limited phase noise targeted to act inside the synchrotron frequency spread, which is itself modified both by the second RF system and by intensity effects (beam loading and others). For a high intensity beam these latter effects can lead to a non-uniform emittance blow-up and even loss of stability for certain bunches in the batch. In this paper we present studies of the emittance blow-up achieved with high intensity beams under different conditions of both RF and noise parameters.
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| TUPP065 |
Experimental Study of the Electron Cloud Instability in the CERN-SPS
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1688 |
| |
- G. Rumolo, G. Arduini, E. Benedetto, E. Métral, G. Papotti, E. N. Shaposhnikova
CERN, Geneva
- R. Calaga
BNL, Upton, Long Island, New York
- B. Salvant
EPFL, Lausanne
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The electron cloud instability limits the performance of many existing proton and positron rings. A simulation study carried out with the HEADTAIL code revealed that the threshold for its onset decreases with increasing beam energy, if the 6D emittance of the bunch is kept constant and the longitudinal matching to the bucket is preserved. Experiments have been carried out at the CERN-SPS to study the dependence of the vertical electron cloud instability on the energy and on the beam size. The reduction of the physical transverse emittance as a function of energy is considered in fact to be the main reason for the unusual dependence of this instability on energy.
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| TUPP066 |
CERN SPS Impedance in 2007
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1691 |
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- E. Métral, G. Arduini, T. Bohl, H. Burkhardt, F. Caspers, H. Damerau, T. Kroyer, H. Medina, G. Rumolo, M. Schokker, E. N. Shaposhnikova, J. Tuckmantel
CERN, Geneva
- R. Calaga
BNL, Upton, Long Island, New York
- B. Salvant
EPFL, Lausanne
- B. Spataro
INFN/LNF, Frascati (Roma)
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Each year several measurements of the beam coupling impedance are performed in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of its evolution. In parallel, after the extensive and successful campaign of identification, classification and cure of the possible sources of (mainly longitudinal) impedance between 1998 and 2001, a new campaign (essentially for the transverse impedance this time) has started few years ago, in view of the operation of the SPS with higher intensity for the LHC luminosity upgrade. The present paper summarizes the results obtained from the measurements performed over the last few years and compares them to our predictions. In particular, it reveals that the longitudinal impedance is reasonably well understood and the main contributors have already been identified. However, the situation is quite different in the transverse plane: albeit the relative evolution of the transverse impedance over the last few years can be well explained by the introduction of the nine MKE kickers necessary for beam extraction towards the LHC, significant contributors to the SPS transverse impedance have not been identified yet.
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