Author: Cullinan, F.J.
Paper Title Page
TUOAB03 Transverse Coherent Instabilities in Storage Rings with Harmonic Cavities 1061
 
  • F.J. Cullinan, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  • G. Skripka, P.F. Tavares
    MAX IV Laboratory, Lund University, Lund, Sweden
 
  Many current and future synchrotron light sources employ harmonic cavities to lengthen the electron bunches in order to reduce the emittance dilution caused by intrabeam scattering. In some cases, the harmonic cavities may be tuned to fulfill the flat potential condition. For this condition, a large increase in the threshold currents of transverse coupled-bunch instabilities has been predicted and recently, the physical content behind this stabilization has been better understood. With this in mind, an investigation is made into the effectiveness of harmonic cavities for different machines. Frequency domain computations employing Laclare's eigenvalue method have been used to investigate the influence of several machine parameters and the results are presented.  
slides icon Slides TUOAB03 [14.037 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOAB03  
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WEPOW003 Design Considerations of a 7BA-6BA Lattice for the Future Upgrade of SOLEIL 2815
 
  • R. Nagaoka, P. Brunelle, H.C. Chao, F.J. Cullinan, X.N. Gavaldà, A. Loulergue, A. Nadji, L.S. Nadolski, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette, France
 
  Previous studies indicated that adoption of a combination of 7 and 6BA cells in the existing SOLEIL ring enables reaching the target range of the horizontal emittance below 200 pm·rad as expected, in contrast to fewer dipole solutions such as a combination of 5 and 4BA studied earlier (IPAC 2014). However, the previous 7BA-6BA lattice resulted in having unacceptably strong gradients in quadrupoles and dipoles leading to high natural chromaticities. Several schemes that would allow for an improvement are explored, such as shortening the insertion device straight sections by one or two meters to create more space for the magnetic structure, lowering the dipole fields and the use of anti-bends as proposed by A. Streun. The effectiveness of each scheme is evaluated and the best combined use of them for SOLEIL is investigated. Ways to fulfil the constraints of the existing dipole beam lines are studied by introducing longitudinal gradient bends and/or multipole wigglers. The nonlinear optimisation to maximise the on and off-momentum apertures is made by using genetic algorithm-based numerical codes. A comparison of their performance and the obtained results are presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW003  
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WEPOW035 Commissioning of the Harmonic Cavities in the MAX IV 3 GeV Ring 2911
 
  • G. Skripka, Å. Andersson, A.M. Mitrovic, P.F. Tavares
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F.J. Cullinan, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
 
  The MAX IV 3 GeV storage ring operates with beam of high current and ultralow emittance. These beam parameters in combination with the small effective aperture enhance possible collective beam instabilities. Three passive harmonic cavities are installed to introduce bunch lengthening and tune spread, leading to decoupling of the bunch spectrum from the machine effective impedance and mitigating instabilities by Landau damping respectively. In this paper we present the first results of the commissioning of the passive third harmonic cavities in the MAX IV 3 GeV ring. The additional harmonic cavity potential significantly improved the beam lifetime. First observations of the harmonic cavity effect on the damping of collective beam instabilities are discussed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW035  
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