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Characterization of Fast Orbit Feedback System

Characterization of Fast Orbit Feedback System. Om Singh, APS, ANL NSLS-2 Beam Stability Workshop BNL, April 18-20, 2007. Outline. Bpm & Magnet Layout – One SR Sector AC Beam Stability Goals & Present Performance Orbit Feedback Sub-systems Resolution & Responses

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Characterization of Fast Orbit Feedback System

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  1. Characterization ofFast Orbit Feedback System Om Singh, APS, ANL NSLS-2 Beam Stability Workshop BNL, April 18-20, 2007

  2. Outline • Bpm & Magnet Layout – One SR Sector • AC Beam Stability • Goals & Present Performance • Orbit Feedback Sub-systems • Resolution & Responses • Digital Process Rate & Orbit Correction Configuration • Summary & Upgrade Plans • Photo

  3. One Sector of the Advanced Photon Source Storage Ring 27.6 Meters Number of sectors = 40 Circumference = 1104 m Transverse Tunes νx= 36.2, vy = 19.27 Energy = 7 GeV Beam Current = 102 mA RF Frequency = 352.194 MHz Revolution Frequency = 271.554 KHz Harmonic number = 1296

  4. Beta Functions

  5. Beam Position Monitors and Dipole Magnets One Sector - Cartoon • X-Ray Beam Position Monitors • Photo -emission sensory blades • Excellent thermal insulation • and vibration damping • Beam Position Measurement BW up to Tens of KHz Sector N Elliptical Chamber PUEs ID Chamber PUEs ID Device • Monopulse BPM – turn by turn (AM/PM) • Up to 8000 turn-by-turn samples • of beam history - @ ~ 271 KHz • Averages to 50 Hz, 2 Hz, 0.03 Hz BW Bending Magnet Slow Correction Magnet Fast Correction Magnet • Narrowband (Switching) BPM • Small Bunch Pattern & Intensity Dependence (vs Mp bpm) • High Reliability and easy maintainability • Beam Position Measurements BW up to ~ 5KHz

  6. AC Beam Stability Goals • SR Emittance εe= 3.1 nm; coupling = 0.8% • Presently σx = 280 μm; σy = 10 μm; σ’x = 12 μrad; σ’y = 3 μrad • Beam stability goal and present performance • Stability goal* (AC)  5% of the APS beam size/ divergence Goal / Present Performance x, y (μm rms ) x’, y’ (μrad rms ) Goal (0.017 – 200 Hz)  14.0, 0.5 0.60, 0.22** Present (0.017 – 200 Hz)  6.0, 2.0 0.26, 0.34 Broadcast (0.017 – 30 Hz)  0.8, 0.6 *G. Decker presented to 2005 DOE-BES Review at APS ** Includes photon divergence contribution, 7th harmonics, APS undulator A

  7. AC Stability @ ID’s Sources 4 um Correction BW 1.5 um

  8. AC Pointing Stability @ ID’s Sources 220 nrad Spec * G. Decker – DOE-BES Review 2005

  9. 20 Double Sector Processors 1 Master Processor 1 IOC Processor (Datapool) Reflective Memory Network Global 1.5 KHz Processing Architecture

  10. Orbit Feedback - Subsystems Subsystems & Performance Limiting Factors 1. BPM/ Corrector - Resolution 2. BPM/ Corrector - Responses 3. DSP Processing Power - Process Rate & Orbit Correction Configuration

  11. Beam Motion @ ID Source vs Bpm Resolution (Noise) 30 Hz Band 30 Hz Band Cumul RMS 30 Hz band (H & V) Beam Motion = 0.8 & 0.6 micron RfBpm Noise = 0.3 & 0.35 micron  Faster digitization should lower noise floor XBpm Noise = 0.04 & 0.04 micron  Low noise level, but so far only in DC orbit feedback Digitizer Noise = 0.01 & 0.01 micron

  12. BPM / Fast Corrector – Responses BPM Response One pole low pass filter @ 2KHz Fast Corrector Response One pole low pass filter @ 1.5 KHz Delay ζ = 0.2 ms BPM & Fast Corrector Combined Phase Contribution @ 100 Hz = 15o @ 200 Hz = 27 @ 300 Hz = 45 @ 400 Hz = 57 @ 500 Hz = 70

  13. Orbit Feedback - Limitations • Digital Signal Processor - • Present hardware allows to process up to 1.5 KHz sample rate – limits orbit correction BW to 50-90 Hz • Up to 4 Bpms per sector are included due to processing time constraint • Study in progress to include Xbpms • Corrector • Only one corrector (A3) available with fast response – limits orbit correction • A second fast corrector is required for optimal orbit correction – simulation shows further noise reduction by ~ 2.5 RFBpms XBpms Fast  Corrector

  14. Optimized Overall O. L. Responses (Vert) – 1.5 KHz vs 15 KHz • Optimized parameters @ 1.5 KHz s.r. • Digital Process Rate = 1.5 KHz • Digitization Phase = (f/fs) * (360deg) • Regulator • 1 HPF @ 0.07 Hz • 1 LPF @ 25 Hz • Gain = 4 • Orbit Correction Bandwidth • 100 Hz o o Unit gain line • Optimized Parameters @ 15 KHz s.r. • Digital Process Rate = 15.0 KHz • Digitization Phase= (f/fs) * (360deg) • Regulator • 1 HPF @ 0.105 Hz • 1 LPF @ 75 Hz • Gain = 6 • Orbit Correction Bandwidth • 400 Hz

  15. Summary – Stability Goals, Status & Plans • AC Beam Stability • (0.017 – 200 Hz) • Horizontal beam stability goals are met • Vertical beam stability requires a factor • of ~ 4 improvement • Proposed Upgrade Plans • Add 2nd fast corrector per sector - simulation shows noise reduction factor is 2.5 • Increase process rate ten-fold > 15 KHz - AC obit correction BW to 400 Hz • Improve RfBpm noise floor – increase digitization rate • Include Xbpms in fast orbit feedback

  16. Bpm/ Corrector In-Use Status – Orbit Feedback R F B P M s Xbpms Vertical Horizontal Fast Corr  Configuration Layout – L. Erwin

  17. Photo

  18. In Tunnel BPM Hardware (Rf Bpms) Elliptical Chamber Buttons & Matching Networks Small Gap Chamber Buttons Filter & Comparator Photo – M. Hahne

  19. In Tunnel BPM Hardware (Xbpms) Xbpm Main Assembly X-Y Translation Stages Mounting Stand Xbpm Blades Assembly * Deming Shu -APS

  20. Outside Tunnel Hardware BPM Front-End Electronics and Processors – Two Sectors X-ray BPMs Interface RF Bpms & Processors  Patch Panel Narrowband RFbpms   Pre-Amps  16 Bits ADCs FDBK Processors  AM/PM RFBpms  Filters &Controls BPM IOC Photos by M. Hahne

  21. Acknowledgement To All APS members for contribution to support ongoing Beam Stability work

  22. BPM Hardware Development Highlight • RF Bpms • Mpbpm data acquisition* upgrade in progress, using fast 88 MHz A/D and FPGA technology; can provide bunch by bunch position data • Evaluation of yet another kind BPM in progress from Instrumentation Technology (Libera) – ALL digital bpm with direct sampling of each button RF signals. Two units are in hand & evaluation with beam to follow • Photoemission type - Xbpm • BM Xbpm – extremely reliable; used in DC Orbit control routinely • ID Xbpm – “Decker distortion” has been completed redirecting unwanted stray radiations away from ID radiations. Provides beam measurement to sub-micron level at fix gap. When gap varies, photon beam measurement held to tens of microns with feedforward algorithm • Xbpm – hard X-ray type Bpm under development; to resolve to sub-micron level even with ID gap change; has potential for beamline alignment gold standard

  23. (G. Decker)

  24. * * G. Rosenbaum & G. Decker

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