CM18 Ecloud/TMCI Feedback Progress and future directions J.D. Fox 1 - - PowerPoint PPT Presentation

e-Cloud/TMCI What’s New MD results What’s New - Models Summary Recent Publications Extra

CM18 Ecloud/TMCI Feedback

Progress and future directions J.D. Fox1

LARP Ecloud Contributors:

• J. Cesaratto1, J. D. Fox1, M. Pivi1, K. Pollock1, C. Rivetta1, O. Turgut1, S. Uemura1
• G. Arduini2, W. Hofle2, K. Li2,G. Rumolo2, B. Salvant2
• M. Furman3, M. Venturini3, S. De Santis3, Z. Paret3, R. Secondo3, J.-L. Vay3
• A. Drago4, S. Gallo4, F. Marcellini4, M. Zobov4

1Accelerator Research Department, SLAC 2BE-ABP-ICE Groups, CERN 3Lawrence Berkeley Laboratory 4LNF-INFN

• J. D. Fox

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SPS Ecloud/TMCI Instability R&D Effort

Motivation - control Ecloud and TMCI effects in SPS and LHC via GHz bandwidth feedback Ongoing project SLAC/LBL/CERN via US LARP Proton Machines, Ecloud driven instability - impacts SPS as high-current LHC injector

Photoelectrons from synchrotron radiation - attracted to positive beam Single bunch effect - head-tail ( two stream) instability

TMCI - Instability from degenerate transverse mode coupling - may impact high current SPS role as LHC injector Multi-lab effort - coordination on

Non-linear Simulation codes (LBL - CERN - SLAC) Dynamics models/feedback models (SLAC - LBL-CERN-Stanford STAR lab) Machine measurements- SPS MD (CERN - SLAC - LBL) Kicker models and simulations ( LNF-INFN,LBL, SLAC) Hardware technology development (SLAC,)

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Organization and People - Some welcome new faces

SLAC J. Fox (50%), K. Li, C. Rivetta(50%), J. Olsen, J. Dusatko(30%), M. Pivi(20%)

• J. Cesaratto ( Toohig Fellow)

Ozhan Turgut, K. Pollock ( Stanford Graduate Students ) CERN - W. Hoefle, B. Salvant, U. Wehrle SPS/LHC Transverse Feedback MD planning and MD measurements TMCI simulations and measurements LBL J-L Vay, M. Furman, Z. Paret R. Secondo, S. De Santis Kicker study, Ecloud Simulation effort (WARP), Pickup Equalizer LNF-INFN F . Marcellini, S. Gallo, M. Zobov, A. Drago Kicker study, Impedance estimates

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Recent efforts and Recent progress

Length Trigger Injection Recorder Function Excitation Σ Y ∆ Delay, RF ~ Power Amps Excitation Master RF Synch Memory D/A Sequence Kicker Beam Pickups Receiver Data Offline Transfer

'

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Kicker Options Design Study

LNF-INFN,LBL and SLAC Collaboration. Excellent progress 2012 Goals - evaluate 3 possible options

Stripline (Arrays? Tapered? Staggered in Frequency?) Overdamped Cavity ( transverse mode) Slot and meander line ( similar to stochastic coooling kickers)

Based on requirements from feedback simulations, shunt impedance, overall complexity - select path for fab

5-2000 8545A13

vout vout Beam

'

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Kicker Options - Ideas from S. De Santis and Z. Paret

Study of multiple striplines for bandwidth and overall shunt impedance RF models and estimates

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Kicker Options - Idea from S. Gallo

Use 25 ns interval between bunches, have kicker with 20 ns fill time High shunt impedance, requires more complex off-diagonal processing, input and output data at different rates !! "#$%&'!()! "#$%&'!(*! "#$%&'!(+! ,-.&! !"#$%&$'() *+,$"-.)/0112)3(45)673() *+,$"-.)/0112)3(45)673() +/01!23405#067! 8*)9):22)0;<) =22)>)1?)0;<) 1@22)>)1?)0;<) 8&4967! 1A)B6) 1C)B6) 12)B6) :#;;#49!<=&! 25?)'D) 12)'D) 12)'D) >8! EEE) @C) F=) ?7@46!A=.&034$&! G)15C)HI)JK)8*L) G)15C)HI)JK)=22)0;<L) G)@5@)HI)JK)1@22)0;<L) Assuming that each kicker is powered by a 1 kW source covering the entire device bandwidth, the resulting transverse voltage transferred to the beam as a function

• f the frequency is

shown in the following plot.

• J. D. Fox

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Kicker Options - Idea from J. Cesaratto

similar to stochastic cooling kickers wideband - ( longitudinal Impedance estimate in progress by M. Zobov)

0.0 0.5 1.0 1.5 2.0 10000 20000 30000 40000 50000 60000

Frequency (GHz) Shunt Impedance ()

• J. D. Fox

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System Development for MD studies

4 GS/sec bunch-synchronized random excitation system with GUI Broadband 80W 20 - 1000 MHz amplifiers

Not ideal, useful for MD studies Chassis , couplers, remote control for tunnel hardware

Hardware equalizer for real-time front end

500 1000 1500 1 2 SPS Proton Distribution Proton Index 5 10 15 20 25 30 −1 1 Applied signal (Turn 1 after warm−up) Samples Amplitude 10 20 30 100 150 200 −1 −0.5 0.5 1 Samples Applied Signal (Turns 101:200) Turns

• J. D. Fox

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Hardware Equalizer

Pickup response distorts beam signals Long cables also have nonlinear phase response Existing software equalizer used in matlab data processing we need a real-time ( hardware) equalizer for processing channel Started by R. Secondo, now K. Pollock

• J. D. Fox

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4 Gs/sec. 1 stack SPS feedback channel

We are building a proof-of-principle channel for closed loop tests in SPS before the 2013 shutdown, using existing kicker and excitation system Flexible reconfigurable processing - evaluate multiple processing algorithms

• J. D. Fox

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Proof of Principle processing

• 4%-5(3,)(#6+)7)'18)+9

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Prototype using FPGA evaluation board

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• J. D. Fox

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4 GS/sec ADC daughtercard

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• J. D. Fox

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4 GS/sec D/A daughtercard with synchronization and timing functions

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• J. D. Fox

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Driven Beam Motion MD Experiments July/August, November 2011 and April 2012

Goal: Drive individual sections of the bunch - Estimate Models Excitation - Power Stage - Vertical displacement measurement. Estimate bunch reduced dynamical model in open loop- Below e-cloud instability

• threshold. Increase currents

and study dynamics change Compare MD results to macro-particle simulation codes

Drive individually different areas of the bunch (Excitation - Amplifier - Kicker) Measure with scope the receiver signals ∆ − Σ. Estimate vertical displacement for different sections of the bunch. Based on Input-Output signals, estimate bunch reduced model.

• J. D. Fox

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Excitation MD July/August, Nov 2011 and April 2012

Significant developments and sophisticated analysis

Excitation methods ( chirps, random, selected modes) ability to clearly excite through mode 4

• J. D. Fox

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Vector (Modal) Analysis of Beam Motion J. Cesaratto

We excite the beam from our amplifier array Study motion via pickup array, receiver system, digitize at 40 GS/sec. Plot slice phase at modal frequency Barycentric mode 0 motion

0.01 0.02 0.03 30 210 60 240 90 270 120 300 150 330 180 Turn # 7700

• J. D. Fox

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Progress - Techniques to time a selected bunch and position ( O. Turgut)

We excite the beam from our amplifier array To control the modes excited, we must have precision in excitation timing an off-time Mode 0 excitation will excite mode -1, 1

methods to repeatably position the kick, time the system methods to maximize the effective kick applied to the beam

Beam Excitation Waveform Generator Manual Colby Delay Box Amplifiers Kicker

Barycentric driven motion

2000 2500 3000 3500 4000 4500 5000 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2x 10

Time Delay (ps) Max Rms Value of Vertical Motion Max RMS of Vertical (Head Tail) Motion vs Time Delay 2012 April MD

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Progress in Simulation Models

Significant efforts, including feedback to WARP , Head-Tail and CMAD Significant progress, especially in understanding numeric noise in models, impact on feedback noise model Still needs realistic channel noise study, sets power amp requirements Still needs more quantitative study of kicker bandwidth requirements Head-tail offers path to evaluate TMCI and feedback methods Critical to validate simulations against MD data Continued progress on linear system estimation methods Add realistic components to the feedback channel - CMAD / HeadTail / Warp

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Bunch is sampled in z using 64-80 samples (equal charge - equal distance) Receiver, processing channel, amplifier, kicker include frequency response, signal limits and noise. Processing channel can operate from 1 to 64 samples to model different sampling rates.

• J. D. Fox

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CM18 Ecloud/TMCI Progress

Kicker design/estimation effort

Significant progress, welcome contributions from LBL, LNF-INFN and SLAC. Important Milestone - recommendation of geometry for CERN fab, SPS installation

Continued development SPS 4 GS/sec. vertical excitation system

System with 4 85W 20-1000 MHz amplifier array, excitation system Used for MD measurements Summer 2011, Nov 2011, April 2012 Increasingly sophisticated analysis codes Results show ability to excite through mode 4, value of beam diagnostic tool

Understand Ecloud/TMCI dynamics via MD data, reduced models and numeric simulations

Extraction of system dynamics, development of reduced (linear) coupled-oscillator model for feedback design estimation Inclusion of feedback models in WARP , CMAD and Head-Tail codes

Design progress - 4 GS/sec processing demonstration prototype

FPGA platform, with D/A and A/D daughtercards in fab Builds on existing timing and amplifier system for proof of principle tests

• J. D. Fox

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Research Goals 2012 and Beyond

Technology R&D - specification of wideband feedback technical components Technical Analysis of options, specification of control requirements

Single bunch control ( wideband, vertical plane) - Required bandwidth? Control Algorithm - complexity? Flexibility? Machine diagnostic techniques? Fundamental R&D in kickers, pickups - technology demonstration in SPS

Develop proof of principle processing system, evaluate with machine requirements System Design proposal and technical implementation/construction plan Plans 2012-2013

Develop a technology small-scale prototype, develop wideband kicker Functionality to test feedback techniques on a subset of bunches, evaluate options Excellent Ph.D. material ( accelerator physics, nonlinear control), can support several students

We will learn from a limited "quick prototype" at the SPS Can then confidently design a true operational system for SPS, and if desired, LHC

• J. D. Fox

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• J. Cesaratto, et al Excitation of Intra-bunch Vertical Motion in the SPS - Implications for

Feedback Control of Ecloud and TMCI Instabilities Proceedings IPAC12

• S. De Santis, et al Study of a Wideband Feedback Kicker for the SPS Proceedings IPAC12
• M. Venturini, et al Analysis of Numerical Noise in Particle-In-Cell Simulations of

Single-Bunch Transverse Instabilities and Feedback in the CERN SPS Proceedings IPAC12

• C. Rivetta, et alFeedback System Design Techniques for Control of Intra-bunch Instabilities

at the SPS Proceedings IPAC12

• C. Rivetta, et al Reduced Mathematical Model of Transverse Intra-bunch Dynamics

Proceedings IPAC12

• J. Fox et al A 4 GS/s Synchronized Vertical Excitation System for SPS Studies - Steps

Toward Wideband Feedback Proceedings IPAC12

• M. Pivi, et al Simulation Code Implementation to Include Models of a Novel Single-bunch

Instability Feedback System and Intra-beam Scattering Proceedings IPAC12

• T. Mastorides, et al, Radio frequency noise effects on the CERN Large Hadron Collider

beam diffusion, PRST-AB 14,092802 (2011)

• T. Mastorides, et al, Studies of RF Induced Bunch Lengthening at the LHC, Proceedings

PAC 11, NY

• T. Mastorides, et al, RF system models for the CERN Large Hadron Collider with

application to longitudinal dynamics, PRST-AB 13:102801,2010

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• C. Rivetta, et al, Mathematical Models of Feedback Systems for Control of Intra-bunch

Instabilities Driven by Eclouds and TMCI, Proceedings PAC 2011, New York

• R. Secondo, et al, Simulation Results of a Feedback Control System to Damp Electron

Cloud Single-Bunch Transverse Instabilties in the CERN SPS, Proceedings PAC 2011, New York J-L Vay, et al, Direct Numerical Modeling of E-cloud Driven Instability of a Bunch Train in the CERN SPS, Proceedings PAC 2011, New York

• O. Turgut, et al, Estimation of Ecloud and TMCI Driven Vertical Instability Dynamics from

SPS MD Measurements - Implications for Feedback Control, Proceedings PAC 2011, New York

• C. Rivetta, et al, Control of Transverse Intra-bunch Instabilities using GHz Bandwidth

Feedback Techniques, Presented at the Ecloud 2010 ICFA Workshop, Ithaca, NY J-L Vay, et al, Numerical modeling of E-cloud Driven Instability and its Mitigation using a simulated Feedback system in the cERN SPS, Presented at the Ecloud 2010 ICFA Workshop, Ithaca, NY

• R. Secondo, et al, Simulated Performance of an FIR-based Feedback System to Control

Electron Cloud Single-Bunch Transverse Instabilities in the CERN SPS, Presented at the Ecloud 2010 ICFA Workshop, Ithaca, NY

• D. Van Winkle, et. al., Commissioning of the LHC Low Level RF System Remote

Configuration Tools Presented at IPAC’10, Kyoto, Japan, 23-28 May 2010, pp TUPEA063

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• J. D. Fox et. al., SPS Ecloud Instabilities - Analysis of Machine Studies and Implications for

Ecloud Feedback, Proceedings IPAC 2010, 23-28 May 2010, Kyoto, Japan. J.-L. Vay et. al., Simulation of E-cloud Driven Instability and its Attenuation Using a Feedback System in the CERN SPS, Proceedings IPAC 2010, 23-28 May 2010, Kyoto, Japan. WEBEX Ecloud Feedback mini-workshop February 2010 (joint with SLAC, Stanford, CERN, and LBL). J.D. Fox, et. al., Feedback Techniques and Ecloud Instabilities - Design Estimates, SLAC-PUB-13634, May 18, 2009. 4pp. Presented at Particle Accelerator Conference (PAC 09), Vancouver, BC, Canada, 4-8 May 2009.

• J. R. Thompson et. al., Initial Results of Simulation of a Damping System of Electron

Cloud-Driven Instabilities in the CERN SPS, Presented at Particle Accelerator Conference (PAC 09), Vancouver, BC, Canada, 4-8 May 2009. Performance of Exponential Coupler in the SPS with LHC Type Beam for Transverse Broadband Instability Analysis 1 R. de Maria BNL, Upton, Long Island, New York, J. D. Fox SLAC, Menlo Park, California, W. Hofle, G. Kotzian, G. Rumolo, B. Salvant, U. Wehrle CERN, Geneva Presented at DIPAC 09 May 2009 WEBEX Ecloud Feedback mini-workshop August 2009 (joint with SLAC, CERN, BNL, LBL and Cornell). J.D. Fox et. al., Feedback Control of Ecloud Instabilities, CERN Electron Cloud Mitigation Workshop 08.

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• W. Hofle, E-cloud feedback activities for the SPS and LHC, CERN Electron Cloud Mitigation

Workshop 08.

• R. De Maria, Observations of SPS e-cloud instability with exponential pickup, CERN

Electron Cloud Mitigation Workshop 08.

• G. Rumolo, Experiments on SPS e-cloud instability, CERN Electron Cloud Mitigation

Workshop 08.

• M. Venturini, Progress on WARP and code benchmarking, CERN Electron Cloud Mitigation

Workshop 08.

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SPS Studies 2009, 2010, 2011

Open-Loop unstable beam measurements Vertical Instability develops within 100 turns. Time domain ,frequency domain studies 1E11 p/bunch Use this technique to compare models, MD data - extract beam dynamics necessary to design feedback. Roughly 25 slices (250 ps) between displacement maxima and minima Spring/summer 2010 - develop 4 Gs/sec. excitation system, drive tapered pickup as kicker pickups and receiver studies Noise, transverse resolution 25 microns rms at 0.5E11 (vertical) Beam Excitation studies, stable beam Develop excitation system with synchronized oscillators Use 20 - 1000 MHz amplifier array, with 200 MHz bandwidth kicker Study internal modes, look for dynamics change as currents increase

50 100 400 300 200 100 100 200 300 400 500

Vertical displacement of bunch 119

slice SUM / DIFF signals (a.u) 50 100 1 0.8 0.6 0.4 0.2 0.2 0.4 0.6 0.8 1 slice Vertical displacement (a.u) SUM DIFF

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