Author: Oeftiger, A.
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MOPOR023 Flat Bunches with a Hollow Distribution for Space Charge Mitigation 652
 
  • A. Oeftiger, H. Bartosik, A. Findlay, S. Hancock, G. Rumolo
    CERN, Geneva, Switzerland
  • A. Oeftiger
    EPFL, Lausanne, Switzerland
 
  Funding: CERN, Doctoral Studentship EPFL, Doctorate
Longitudinally hollow bunches provide one means to mitigate the impact of transverse space charge. The hollow distributions are created via dipolar parametric excitation during acceleration in CERN's Proton Synchrotron Booster. We present simulation work and beam measurements. Particular emphasis is given to the alleviation of space charge effects on the long injection plateau of the downstream Proton Synchrotron machine, which is the main goal of this study.
 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR023  
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WEPOY044 Review of CPU and GPU Faddeeva Implementations 3090
 
  • A. Oeftiger, R. De Maria, L. Deniau, K.S.B. Li, E. McIntosh, L. Moneta
    CERN, Geneva, Switzerland
  • A. Aviral
    BITS Pilani, Pilani, India
  • S. Hegglin
    ETH, Zurich, Switzerland
  • A. Oeftiger
    EPFL, Lausanne, Switzerland
 
  Funding: CERN, Doctoral Studentship EPFL, Doctorate
The Faddeeva error function is frequently used when computing electric fields generated by two-dimensional Gaussian charge distributions. Numeric evaluation of the Faddeeva function is particularly challenging since there is no single expansion that converges rapidly over the whole complex domain. Various algorithms exist, even in the recent literature there have been new proposals. The many different implementations in computer codes offer different trade-offs between speed and accuracy. We present an extensive benchmark of selected algorithms and implementations for accuracy, speed and memory footprint, both for CPU and GPU architectures.
 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY044  
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THPMR036 Improved Methods for the Measurement and Simulation of the CERN SPS Non-linear Optics 3464
 
  • H. Bartosik, A. Oeftiger, M. Schenk, F. Schmidt, M. Titze
    CERN, Geneva, Switzerland
 
  Good knowledge of the non-linear properties of the SPS lattice is crucial for modelling and optimising the machine performance in the presence of collective effects leading to incoherent tune spreads such as space charge, e-cloud and beam coupling impedance. In view of the LHC injectors upgrade (LIU) project and the future SPS operation in a regime dominated by such collective effects, detailed measurements of the SPS non-linear chromaticity and detuning with amplitude have been performed for the two optics configurations presently available for LHC type beams. The measurement results are used to fit systematic multipole components to the main magnets of the SPS MADX model as a basis for the non-linear machine model that can be used for beam dynamics simulations. The implications for the operation of the SPS with the LIU beam parameters are discussed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR036  
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MOPOR021 Space Charge Studies with High Intensity Single Bunch Beams in the CERN SPS 644
 
  • H. Bartosik, F. Schmidt
    CERN, Geneva, Switzerland
  • A. Oeftiger
    EPFL, Lausanne, Switzerland
  • M. Titze
    HZB, Berlin, Germany
 
  In order to reach the target beam parameters of the LHC injectors upgrade (LIU) project the beam degradation due to losses and emittance growth on the long injection plateau of the SPS needs to be minimized. A detailed study of the dependence of losses, transverse emittance blow-up and transverse beam tail creation as function of the working point is presented here for a high brightness single bunch beam with a vertical space charge tune spread of about 0.2 on the 26 GeV injection plateau. The beam behaviour close to important betatron resonances is characterised and a region in the tune diagram with minimal beam degradation is identified. Implications about the performance for LIU beams are discussed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR021  
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