Feedback Control of Electron Cloud Instabilities
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LARP CM12 Napa April 2009

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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 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

C. Rivetta, J. Fox, J. L. Vay Riccardo De Maria

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.

LARP SPS and LHC 6-Year plan*

LARP SPS and LHC 6-Year plan*

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