Keyword: feedback
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MOP2WA04 Recent Results from the Wideband Feedback System Tests at the SPS and Future Plans optics, kicker, coupling, controls 38
 
  • K.S.B. Li, H. Bartosik, M.S. Beck, E.R. Bjørsvik, W. Höfle, G. Kotzian, T.E. Levens, M. Schenk
    CERN, Geneva, Switzerland
  • J.E. Dusatko, J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California, USA
  • M. Schenk
    EPFL, Lausanne, Switzerland
  • O. Turgut
    Stanford University, Stanford, California, USA
 
  A high bandwidth transverse feedback demonstrator system has been devised within the LARP framework in collaboration with SLAC for the LHC Injectors Upgrade (LIU) Project. The initial system targeted the Super Proton Synchrotron (SPS) at CERN to combat TMCI and electron cloud instabilities induced for bunches with bunch lengths at the 100 MHz scale. It features a very fast digital signal processing system running at up to 4~GS/s and high bandwidth kickers with a frequency reach of ultimately beyond 1~GHz. In recent years, the system has gradually been extended and now includes two stripline kickers for a total power of 1~kW delivering correction signals at frequencies of currently more than 700~MHz. This talk will cover recent studies using this demonstrator system to overcome TMCI limitations in the SPS. We will conclude with future plans and also briefly mention potential applications and requirements for larger machines such as the LHC or the HL-LHC.  
slides icon Slides MOP2WA04 [19.091 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA04  
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WEP2PO001 Upgraded Transverse Feedback for the CERN PS Booster betatron, kicker, hardware, booster 256
 
  • A. Blas, G. Kotzian
    CERN, Geneva, Switzerland
 
  A new transverse feedback system is being used for the 4 rings of the CERN Proton Synchrotron Booster (PSB). In addition to transverse instabilities mitigation - within the range of 100 kHz to 100 MHz - the system allows for controlled beam emittance blow-up, machine tune measurement and other optic studies. The system was upgraded in order to multiply by 8 its power (800 W instead of 100 W on each of the 4 kicker electrodes) and in order for its electronic core to employ a digital processing. The transverse feedback adapts automatically to a factor 3 change in the beam revolution period and to any change of the machine tune. It includes an excitation source that combines up to 9 selectable harmonics of the revolution frequency with a selectable amplitude for each. The excitation may be dipolar or quadrupolar. Future possible upgrades will be presented including a setup to tackle half-integer tune values and a digital processing using a fixed clock frequency instead of the revolution frequency clock.  
poster icon Poster WEP2PO001 [1.794 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO001  
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WEP2PO003 Beam Loading and Longitudinal Stability Evaluation for the FCC-ee Rings cavity, beam-loading, impedance, synchrotron 266
 
  • I. Karpov, P. Baudrenghien
    CERN, Geneva, Switzerland
 
  In high-current accelerators, interaction of the beam with fundamental impedance of the accelerating cavities can limit machine performance. It can result in a significant variation of bunch-by-bunch parameters (bunch length, synchronous phase, etc.) and lead to longitudinal coupled-bunch instability. In this work, these limitations are analysed together with possible cures for the high-current option (Z machine) of the future circular electron-positron collider (FCC-ee). The time-domain calculations of steady-state beam loading are presented and compared with frequency-domain analysis.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO003  
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THP2WC02 LLRF Studies for HL-LHC Crab Cavities cavity, emittance, luminosity, betatron 440
 
  • P. Baudrenghien
    CERN, Geneva, Switzerland
  • T. Mastoridis
    CalPoly, San Luis Obispo, California, USA
 
  The HL-LHC upgrade includes sixteen Crab Cavities (CC) to be installed on both sides of the high luminosity experiments, ATLAS and CMS. Two issues have been highlighted for the Low Level RF: transverse emittance growth (and associated luminosity drop) caused by CC RF noise, and large collimator losses following a CC trip. A prototype cryomodule with two CCs has been installed in the SPS, and tests have started in May 2018 with beam. This paper briefly reports on preliminary results from the SPS tests. It then presents emittance growth calculations from cavity field phase and amplitude noise, deduces the maximum RF noise compatible with the specifications and presents a possible cure consisting of a feedback on CC phase and amplitude. To reduce the losses following a CC trip we propose to implement transverse tail cleaning via the injection of CC noise with an optimized spectrum, which selectively excites the particles of large transverse oscillation amplitudes.  
slides icon Slides THP2WC02 [1.943 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THP2WC02  
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