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Characterization of Fast Orbit Feedback System

Explore the detailed characterization of the fast orbit feedback system at APS, focusing on BPM layout, beam stability, resolution, and upgrade plans. Learn about subsystems and performance factors, including BPM responses and limitations.

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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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