Feedback Control of Electron Cloud Instabilities

6-Year LARP R&D Proposal

Mauro Pivi, John Fox

March 2009

LARP 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

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

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

RIccardo De Maria (BNL) et al.

Observations of SPS e-cloud instability with exponential pickup

LARP E-cloud, March 9, 2009 feedback simulations - JL Vay, M Furman

QuickTime™ and aTIFF (Uncompressed) decompressor

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QuickTime™ and aTIFF (Uncompressed) decompressor

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Simulations of e-cloud instability in SPScomparison Warp-Headtail

SPS at injection (Eb=26 GeV)

– =27.729

– Np=1.11011

– Ne=31012 (uniform)

– continuous focusing• x,y= 33.85, 71.87

• x,y= 26.12, 26.185

• z= 0.0059

Warp

Headtail

Fractional emittance growth

horizontal vertical

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

• 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

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

SPS Single-Bunch Feedback System

LARP CM12 Napa 2009

• 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

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

Electron cloud mitigations in the SPS

LARP CM12 Napa 2009

Mauro Pivi, J. Fox (SLAC) et al.LARP CM12 Napa 2009

LARP SPS and LHC 6-Year plan*

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

Decision Point: Feasibility

Mauro Pivi, J. Fox (SLAC) et al.LARP CM12 Napa 2009

• 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

Single-Bunch Feedback System Project Plan 6 years (Resources Dependent)

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Analysis of SPS and LHC beam dynamics studies, comparisons with modelsMD Ecloud Studies and Measurements in the SPSAdaptat SLAC’s transient analysis codes to Ecloud simulation data structuresValidate simulation codes against beam measurements Lab effort- evaluation of 4 GS/sec. D/AProof-of-principal technology R&D on GHz bandwidth (e.g. 2 - 4 GS/sec.) Back-end, kicker, control and affect beamExtraction of system dynamicsDevelopment of “linear” coupled-oscillator model for feedback design Evaluate possible control techniques, understand trade-offsEvaluate feasibility of feedforward/feedback techniquesEstimate limits of techniques, applicability to SPS and LHC needsIdentify critical technology optionsEvaluate difficulty of technical implementation Is a feedback control feasible for SPS single-bunch instability?What techniques are applicable? Modelling of closed-loop system dynamicsEstimation of feedback system specifications Technology R&D and system development Technical analysis of options, specification of control system requirements: Required bandwidth? Control alogorithm - complexity? flexibility? Diagnostic techniques? Fundamental technology: R&D in support of requirements - Kickers and pickups? Wideband RF instrumentation, high-speed digital signal processingSpecification of wideband feedback system technical components Proof of principle processing system, evaluate with machine measurementsPrototype Development: Proof of principle system and MD testing in the SPSSystem Design Proposal and technical implementation/construction project plan

2009-2011 2012-2014

LARP SPS and LHC 6-Year plan*

LARP SPS and LHC 6-Year plan*