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Rumolo, G.

Paper Title Page
MOPP048 Fast Ion Instability in the CLIC Transfer Line and Main Linac 655
 
  • G. Rumolo, D. Schulte
    CERN, Geneva
  
  The Fast Ion Instability is believed to be a serious danger for bunch trains propagating in the CLIC electron transfer line and main linac, since it may strongly affect the bunches in the tail of the train if the vacuum pressure is not below a certain threshold. We have developed the FASTION code, which can track electrons through a FODO cell line and takes into account their interactions with the produced (and possibly trapped) ions. We describe how this tool can be used for setting tolerances on the vacuum pressure and for giving specifications for the design of a feedback system.  
MOPP049 Collective Effects in the CLIC Damping Rings 658
 
  • G. Rumolo, J. B. Jeanneret, Y. Papaphilippou, D. Quatraro
    CERN, Geneva
  
  The possible performance limitations coming from collective effects in the CLIC damping rings are the subject of this paper. In particular, the consequences of space charge, due to the very high beam brilliance, and of the resistive wall impedance, due to the locally very small beam pipe, are considered potentially dangerous in spite of the high beam energy. Hence, they have been studied in detail with the HEADTAIL code, which has been modified in order to take into account a finer lattice structure as well as multi-bunch effects of the resistive wall wake field. The study aims at setting the intensity thresholds determined by these phenomena.  
MOPP050 Electron Cloud Build Up and Instability in the CLIC Damping Rings 661
 
  • G. Rumolo, Y. Papaphilippou
    CERN, Geneva
  • W. Bruns
    WBFB, Berlin
  
  Electron cloud can be formed in the CLIC positron damping ring and cause intolerable tune shift and beam instability. 2D and 3D build up simulations with the Faktor2 code, developed at CERN, have been done to predict the cloud formation in the arcs and wigglers of the damping rings. HEADTAIL simulations have been used to study the effect of this electron cloud on the beam and assess the thresholds above which the electron cloud instability would set in.  
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.  
TUPP066 CERN SPS Impedance in 2007 1691
 
  • 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)
  
  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.  
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.  
TUPP094 Recent Improvements in the Tracking Code PLACET 1750
 
  • A. Latina, H. Burkhardt, G. Rumolo, D. Schulte, R. Tomas
    CERN, Geneva
  • E. Adli
    University of Oslo, Oslo
  • Y. Renier
    LAL, Orsay
  
  The Tracking Code PLACET has recently undergone several improvements. A redesign of its internal data structures and a new user interface based on the mathematical toolbox Octave have considerably expanded its simulation capabilities. Several new lattice elements, optimization algorithms and physics processes have been added to allow for more complete start-to-end simulations. The usage of the AML language and the Universal Parser Library extened its interfacing capability.  
THPC018 Beam Dynamics Issues in the CLIC Long Transfer Line 3017
 
  • J. B. Jeanneret, E. Adli, A. Latina, G. Rumolo, D. Schulte, R. Tomas
    CERN, Geneva
  
  Both the main beam and the drive beam of the CLIC project must be transported from the central production site to the head of the main linacs over more than twenty kilometres. Over such distances chromatic aberrations are substantial. With long distances and large beam currents, detuning and instabilities associated to ion production and multi-bunch resistive wall effects must also be considered. These effects are quantified and simulated. Based on these results, we propose a baseline design for these two lines.