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Feedback Control of Electron Cloud Instabilities6-Year LARP R&D ProposalMauro Pivi, John FoxMarch 2009LARP electron cloud contributors:John D. Fox, Mauro Pivi, Claudio Rivetta (SLAC)Wolfram Fisher, Riccardo De Maria (BNL)John Byrd, M.Furman, Stefano De Santis, Jean-Luc Vay (LBL)Gianluigi Arduini, Wolfgang Hofle, Giovanni Rumolo (CERN)

LARP CM12 Napa April 2009


Observations of SPS e-cloud instability with exponential pickup

Bunch in the first (stable) batch (June)

Bunch in the last (unstable) batch (June and August)

August data (right) after scrubbing period: data filtered from noise

RIccardo De Maria (BNL) et al.

simulations of e cloud instability in sps comparison warp headtail
Simulations of e-cloud instability in SPScomparison Warp-Headtail
  • SPS at injection (Eb=26 GeV)
    • =27.729
    • Np=1.11011
    • Ne=31012 (uniform)
    • continuous focusing
      • x,y= 33.85, 71.87
      • x,y= 26.12, 26.185
      • z= 0.0059

Fractional emittance growth





feedback simulations - JL Vay, M Furman


SPS Single-Bunch

Feedback System

  • Motivations:
    • Actually: max chromaticity mitigates e-cloud but at expense of emittance increases
    • No chromaticity and no scrubbing  e-cloud again
    • Measured bunch distortion also when machine scrubbed in August (caution: filtered data)
    • At higher currents, i.e. upgrade, e-cloud stronger
    • PS2
    • LHC relies on conditioning, SB feedback can be ultimate mitigation

LARP CM12 Napa 2009

Mauro Pivi, J. Fox (SLAC) et al.


Electron cloud mitigations in the SPS

  • Mitigations:
    • Coating good but expensive now (so clearing electrodes, grooves)
    • Installing new chambers
    • Currently scrubbing stainless steel but doesn’t last long, e-cloud may reappear with need of more scrubbing
    • E. Chapochnikova recommended a system to deal with other instabilities, mode coupling etc., and feedback seems the only way
    • Feedback complements coating
    • Upgrade scenarios well beyond 1e11
    • Single-bunch feedback not only for e-cloud but for other instabilities

LARP CM12 Napa 2009

Mauro Pivi, J. Fox (SLAC) et al.


LARP SPS and LHC 6-Year plan*

*with actual resources. Can be a ~3-year plan with increased resources.

Decision Point: Feasibility

LARP CM12 Napa 2009

Mauro Pivi, J. Fox (SLAC) et al.

Strength of the collaboration: excellent communication between 4 laboratories pulling collaborators closely together to benchmark simulation codes, analyze SPS experimental data and modeling feedback system.
  • Single-bunch instability feedback system is not limited to electron cloud but can deal with other sb instabilities

LARP CM12 Napa 2009

Mauro Pivi, J. Fox (SLAC) et al.