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Papotti, G.

Paper Title Page
TUPP059 Study of Controlled Longitudinal Emittance Blow-up for High Intensity LHC Beams in the CERN SPS 1676
 
  • G. Papotti, T. Bohl, T. P.R. Linnecar, E. N. Shaposhnikova, J. Tuckmantel
    CERN, Geneva
  
  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.  
TUPP065 Experimental Study of the Electron Cloud Instability in the CERN-SPS 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
  
  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.  
TUPP067 Transverse Mode-coupling Instability in the CERN SPS: Comparing MOSES Analytical Calculations and HEADTAIL Simulations with Experiments in the SPS 1694
 
  • B. Salvant
    EPFL, Lausanne
  • G. Arduini, E. Métral, G. Papotti, G. Rumolo, R. J. Steinhagen, R. Tomas
    CERN, Geneva
  • R. Calaga
    BNL, Upton, Long Island, New York
  
  Since 2003, single bunches of protons with high intensity (1.2·1011 protons) and low longitudinal emittance (0.2 eVs) have been observed to suffer from heavy losses in less than one synchrotron period after injection at 26 GeV/c in the CERN Super Proton Synchrotron (SPS) when the vertical chromaticity is corrected. Understanding the mechanisms underlying this instability is crucial to assess the feasibility of an anticipated upgrade of the SPS, which requires bunches of 4·1011 protons. Analytical calculations from MOSES and macroparticle tracking simulations using HEADTAIL with an SPS transverse impedance modelled as a broadband resonator had already qualitatively and quantitatively agreed in predicting the intensity threshold of a fast instability. A sensitive frequency analysis of the HEADTAIL simulations output was then done using SUSSIX, and brought to light the fine structure of the mode spectrum of the bunch coherent motion. A coupling between the azimuthal modes -2 and -3 was clearly observed to be the reason for this fast instability. The aim of the present paper is to compare the HEADTAIL simulations with dedicated measurements performed in the SPS in 2007.  
MOPC131 Ions for LHC: Towards Completion of the Injector Chain 376
 
  • D. Manglunki, M. Albert, M.-E. Angoletta, G. Arduini, P. Baudrenghien, G. Bellodi, P. Belochitskii, E. Benedetto, T. Bohl, C. Carli, E. Carlier, M. Chanel, H. Damerau, S. S. Gilardoni, S. Hancock, D. Jacquet, J. M. Jowett, V. Kain, D. Kuchler, M. Martini, S. Maury, E. Métral, L. Normann, G. Papotti, S. Pasinelli, M. Schokker, R. Scrivens, G. Tranquille, J. L. Vallet, B. Vandorpe, U. Wehrle, J. Wenninger
    CERN, Geneva
  
  The CERN LHC experimental programme includes heavy ion physics with collisions between two counter-rotating Pb82+ ion beams at a momentum of 2.76 TeV/c/nucleon per beam and luminosities as high as 1·1027 cm-2 s-1. To achieve the beam parameters required for this operation the ion accelerator chain has undergone substantial modifications. Commissioning with beam of the various elements of this chain started in 2005 and in 2007 it was the turn of the final stage, the Super-Proton-Synchrotron (SPS) following extensive changes to the low-level RF hardware. The major limitations of this mode of operation of the SPS (space charge, intra-beam scattering) are presented, together with the performance reached so far. The status of the pre-injector performance will also be reviewed together with a description of the steps required to reach nominal performance.  
THPC144 A Beam Quality Monitor for LHC Beams in the SPS 3324
 
  • G. Papotti
    CERN, Geneva
  
  The SPS Beam Quality Monitor (BQM) system monitors the longitudinal parameters of the beam before extraction to the LHC to prevent losses and degradation of the LHC luminosity by the injection of low quality beams. It is implemented in two priority levels. The highest level is related to machine protection, e.g. verifying SPS-LHC synchronization and global beam structure. If the specifications are not met, the beam is dumped in the SPS before extraction. On the second level, individual bunch position, length and stability are checked for beam quality assessment. Tolerances are adapted to the mode of operation and extraction to the LHC can also be inhibited. Beam parameters are accessed by acquiring bunch profiles with a longitudinal pick up and fast digital oscilloscope. The beam is monitored for instabilities during the acceleration cycle and thoroughly checked a few ms before extraction for a final decision on extraction interlock. Dedicated hardware and software components implementing fast algorithms are required. In this paper the fast algorithms and their possible implementations are presented.