Author: Fukuma, H.
Paper Title Page
TUPIK059 Recent Progress of Dithering System at SuperKEKB 1827
 
  • Y. Funakoshi, H. Fukuma, T. Kawamoto, M. Masuzawa, S. Nakamura, K. Ohmi, T. Oki, S. Uehara
    KEK, Ibaraki, Japan
  • P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, C. Rimbault
    LAL, Orsay, France
  • A.S. Fisher
    SLAC, Menlo Park, California, USA
  • U. Wienands
    ANL, Argonne, Illinois, USA
 
  Recent progress of the dithering system at SuperKEKB is described. Some details of the system layout are shown. Beam orbit and optics related issues are discussed. Preliminary tests of the some components in the Phase 1 beam commissioning or in the bench are described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK059  
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WEPIK075 Electron Cloud Instability in SuperKEKB Phase I Commissioning 3104
 
  • K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama
    KEK, Ibaraki, Japan
 
  Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK075  
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THPAB022 Ion Instability in SuperKEKB Phase I Commissioning 3741
 
  • K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama
    KEK, Ibaraki, Japan
 
  Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB022  
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