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BIW06, FNAL, May 1~4, 2006

Commissioning of the FPGA-Based Transverse and Longitudinal Bunch-by-Bunch Feedback System for Taiwan Light Source Kuo-Tung Hsu on behalf of the feedback team NSRRC Hsinchu 30076, Taiwan May 2, 2006. BIW06, FNAL, May 1~4, 2006. Outline. I. Introduction II. Feedback Processor

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BIW06, FNAL, May 1~4, 2006

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  1. Commissioning of the FPGA-Based Transverse and Longitudinal Bunch-by-Bunch Feedback System for Taiwan Light Source Kuo-Tung Hsu on behalf of the feedback team NSRRC Hsinchu 30076, Taiwan May 2, 2006 BIW06, FNAL, May 1~4, 2006

  2. Outline I. Introduction II. Feedback Processor III. Transverse Feedback System IV. Longitudinal Feedback System V. Summary BIW06, FNAL, May 1~4, 2006

  3. I. Introduction • TLS is a 1.5 GeV light source. • Dedication in October 1993. • Instabilities are severe in the operation of last decade. • SRF upgrade in Dec. 2004. • Routine top-up operation is started from Oct. 2005. • FPGA-based transverse and longitudinal feedback • system are deployed in Dec. 2005 and Feb. 2006. BIW06, FNAL, May 1~4, 2006

  4. II. FPGA Based Feedback Processor • Adopted form the design of SPring-8. • Minor modification in FPGA code. • USB 2.0 interface is supported. • Up to 20 taps FIR filter is supported for transverse feedback. • Up to 50 taps FIR filter is supported for longitudinal feedback. • Up to 10 (20) decimation factor is supported. => only useful for longitudinal feedback. BIW06, FNAL, May 1~4, 2006

  5. Structure of the Feedback Processor 12 Bit 12 Bit 12 Bit 12 Bit FIFO FIFO FIFO FIFO FIR Filter* FIR Filter* FIR Filter* FIR Filter* DAC 500 MS/sec ADC 125 MS/sec FPGA: Xilinx VirtexII Pro XC2VP70-6FF1517C 4:1 MUX 12 Bit Delay FIFO DDR F/F FIR Filter* 12 Bit DDR F/F 20-tap FIR Filter 20-tap FIR Filter 12 Bit DDR F/F 50-tap FIR Filter 12 Bit 4:1 MUX Delay FIFO DDR F/F Delay Adj. 4:1 MUX 12 Bit Delay FIFO DDR F/F x2 to 249.83 MHz 499.65 MHz fRF/4 = 124.91 MHz DDR SDRAM, 128 Mega Samples X 4 PLL BIW06, FNAL, May 1~4, 2006

  6. Feedback System Environment • Linux/PC : • * Feedback Processor Linux Driver support • USB 2.0 access • * Matlab interface • Control database interface • Feedback processor register access • Captured bunch oscillation data access • Feedback filter design • Data analysis • * Control console Linux (CentOS Distribution) Control Network USB 2.0 Interface => Register access => Memory access Transverse Kicker Transverse and Longitudinal Pickup Bunch Oscillation Detector Back-end Electronic and Power Amplifiers Feedback Processor Longitudinal Kicker BIW06, FNAL, May 1~4, 2006

  7. III. Transverse Feedback System • 1995 Commissioning of the analog feedback system. • * Only vertical instability is a problem. • * Longitudinal instability is severe. • Second tuner was introduced to RF cavities to shift HOM frequency. • * Longitudinal instability is still severe. • * Transverse instability can be controlled by optimized position of the second tuner. • 2004.12 SRF put into operation. • * Both horizontal and vertical instability are strong. • * Difficult control by over compensatedchromaticity. • 2005.04 Analog transverse feedback loop is put back into service again • * Both plane instability was suppressed, however, tune dependence is strong. It is not easy to operate the machine with 0.1% flux • stability. BIW06, FNAL, May 1~4, 2006

  8. 2005.10.12 Start top-up operation @ 200 mA 2005.11.29 Commissioning of the new transverse feedback system. * To solve the sensitivity problem of tune dependence. * To provide better damping for high current operation. * Increase injection efficiency by reduce chromaticity. => High injection efficiency is essential for top-up operation. 2005.11.30 New digital transverse feedback system commissioning and put into service immediately. 2005.12 Start top-up operation at 300 mA BIW06, FNAL, May 1~4, 2006

  9. Block Diagram of the New Transverse Feedback System Feedback Processor D 4 ns A B # 1, 5, 9, .. 197 156 MHz LPF 2 ns ADC 20tapFIR ch 1 C D 20 dB # 3, 7, 11, .. 199 ch 3 20tapFIR ADC # B DACs 933 MHz LPF LNA 4 ns Divider # 2, 6, 10, .. 198 46 dB ADC 20tapFIR ch 2 20 dB # 4, 8, 12, .. 200 Clock/4 = 124.913 MHz ch 4 # B ADC 20tapFIR Divider 2 Vp-p X 4 # A 124.913 MHz Clock/4 = 124.913 MHz Clock FPGA LVDS BBF Clock Generator Transverse Kicker 250 W fRF 499.654 MHz 20 dB 53 dB B 20 dB AR 250A250 20 dB D 20 dB 53 dB 10 KHz ~ 250 MHz BIW06, FNAL, May 1~4, 2006

  10. Layout of pickup & kicker R3 R2 R4 Location bx(m)by(m)nxny hx(m) R5 BPM1 11.3 5.4 4.876 3.018 0.033 R5 Kicker 4.5 2.7 5.572 3.232 0.397 Target Working Point (nx, ny) = (7.312, 4.168) Tunability Dn ~ 0.05 C = 120 m Trev = 400.2 ns Frev = 2.49827 MHz 80 nsec Feedback Electronics R5BPM1 (B - D) 150 nsec R5 R1 R6 Kicker (B - D) BIW06, FNAL, May 1~4, 2006

  11. Response of the Prototype FIR Filter Parameters of the Transverse Feedback System Target Tune Feedback Loop Tunability Working tune bandwidth (change in arbitrary way) nx: 716 kHz ~ 822 kHz (7.285 ~ 7.328) => dn > 0.04 ny: 400 kHz ~ 480 kHz (4.16 ~ 4.192) => dn > 0.03 Negative chromaticity Nominal setting (SF, SD) = (151 Amp, 124 Amp) => (SF, SD) = (121 Amp, 114 Amp) => Beam is still stable => (SF, SD) = (100 Amp, 100 Amp) => Beam is still stable However, beam loss suddenly when turn off the feedback loop BIW06, FNAL, May 1~4, 2006

  12. Beam spectrum observation – Feedback OFF and ON Beam spectrum observation (without longitudinal feedback) Feedback OFF Feedback ON BIW06, FNAL, May 1~4, 2006

  13. Snapshot of Synchrotron Radiation Beam Profile (w/o Longitudinal Feedback) Grow/Damp test results @ 300 mA Horizontal Loop Open Vertical Horizontal Vertical Modal Spectrum Loop Closed BIW06, FNAL, May 1~4, 2006

  14. Current Status of the Transverse Feedback System • Stable operation have been achieved in users shift. • Better than 10-3photon flux stability can be achieved routinely. • Various feedback filters will be tested in a short-term to probe the possibility to improve system performance. • Improve various components form operation point of views are under way. BIW06, FNAL, May 1~4, 2006

  15. IV. Longitudinal Feedback System • Longitudinal instability is serve during last decade operation of TLS. • Optimized the second tuner position and RF gap voltage modulation is the tools to deal this instability with the cost of large energy oscillation. • After SRF upgrade • Strength of the longitudinal is weaker than before. • Mode pattern are much simple. • Longitudinal feedback system are used to lift the residue instabilities. • 2006.01 New longitudinal kicker installed. • 2006.02.06 Longitudinal feedback system commissioning. BIW06, FNAL, May 1~4, 2006

  16. Adaptation of the SLS Longitudinal Kicker to the TLS LFB System • Modified from the DAΦNE and BESSY kickers (four ridged waveguide damper; nose cone) • Center frequency @ 1375 MHz, BW > 250 MHz • Highest shunt impedance ~ 1500 Ω • A few higher order modes are trapped in the structure and are damped by a hybrid TE/TM coupler • Successful operation of the SLS longitudinal kicker • Easy adaptation to the TLS storage ring with minor modifications (nearly rectangular 28 x 88 mm beam pipe elliptical, 38 x 80 mm beam pipe) • Variation of group delay across the operation bandwidth found (~ 600 ps) • Symmetrical excitation to minimize transverse kick due to field non-uniformity Summary of Measured Longitudinal Kicker Performance BIW06, FNAL, May 1~4, 2006

  17. Parameters of the Longitudinal Feedback System Response of the Prototype FIR Filter BIW06, FNAL, May 1~4, 2006

  18. Layout of pickup & kicker R3 ns ~ 0.0136 C = 120 m Trev = 400.2 ns frev = 2.49827 MHz fs = frev/4 = 625 kHz R2 R4 Feedback Electronics Beam Position Monitor (Energy Oscillation Detector) Power Amplifier R5BPM4 (A+B+C+D) R1 R5 Longitudinal Kicker (Energy Correct Kick) Longitudinal Kicker R6 BIW06, FNAL, May 1~4, 2006

  19. 30 dB 20 dB Block Diagram of the Longitudinal Bunch-by-Bunch Feedback System I-Tech’s RF Front-End Buffer and Delay Module S # 1, 5, 9, .. 197 A B ADC 50tapFIR 8 ns # 2, 6, 10, .. 198 D C X 3 ADC 50tapFIR DAC 6 ns 499.654 MHz # 3, 7, 11, .. 199 ADC 50tapFIR 4 ns # 4, 8, 12, .. 200 Clock/4 = 124.913 MHz ADC 50tapFIR X 4 2 ns Clock/4 = 124.913 MHz Clock FPGA 124.913 MHz LVDS BBF Clock Generator 499.654 MHz 200 W SSB Or QPSK Modulator 53 dB Longitudinal Kicker Milmega AS0814-250R 0.8 GHz ~ 1.4 GHz 1500 MHz (SSB) or 1375 MHz (QPSK) BIW06, FNAL, May 1~4, 2006

  20. SSB Modulator Beam Spectrum QPSK Modulator Sirenza STQ-2016 700-2500 MHz Direct Quadrature Modulator Phase Shifter MiniCircuits Amplifier 499.654 MHz RF Output Frequency Multiplier I Shut-down control Q Excitation On/Off Control AD8131 Differential Amplifier PULSAR QE-14-442 90o Hybrids (2~250 MHz) Monitor 0o Correction Signal USB or LSB Selection 90o BIW06, FNAL, May 1~4, 2006

  21. Temporal Behavior of Longitudinal Instability Build-up Loop Open 40 msec Longitudinal Instability Signal Loop Open 100 msec BIW06, FNAL, May 1~4, 2006

  22. Beam Phase and Beam Spectrum with Feedback Loop Open and Closed Beam Spectrum (Open-Loop vs. Closed-Loop) Filling Pattern Beam Phase w/o LFB Beam Phase w LFB 62.5 MHz peak is due to filling pattern with 16 nsec periodicity 2nd harmonic of 62.5 MHz Beam Spectrum Details w/o and w LFB BIW06, FNAL, May 1~4, 2006

  23. Longitudinal Grow/Damp Experiments @ 250 mA BIW06, FNAL, May 1~4, 2006

  24. Snapshot of the Synchrotron Radiation Beam Profile Streak Camera Observation One Turn Loop Open Loop Open Loop Open Loop Open One Turn Loop Closed Loop Closed -> Open -> Closed One Turn Loop Closed BIW06, FNAL, May 1~4, 2006

  25. Current Status of the Longitudinal Feedback System • Stable operation have been achieved in users shift. • Increase the beam brilliance at the results. • Various feedback filters will be try to improve system performance. • Improve aspect form operation point of views are same as transverse feedback system. BIW06, FNAL, May 1~4, 2006

  26. V. Summary • Two major upgraded have been completed recently for the TLS. • - SRF cavity • - Top-up operation • Transverse feedback system upgrade from analog to digital system in late 2005. • Longitudinal feedback system commissioning successful in early 2006. • Both the transverse and longitudinal feedback loop adopt the same feedback processor - SPring-8 designed feedback processor. • Modified SLS longitudinal kicker is used. • SLAC analysis code is adopted for transient signal analysis. • Both systems put into service immediately after commissioning. • Improved the system performance and functionality is on going. BIW06, FNAL, May 1~4, 2006

  27. Acknowledgements Many peoples contributed to this project directly or indirectly. Thanks for their help. T. Nakamura, K. Kobayashi (JASRI/SPring-8) M. Dehler (SLS/PSI) M. Tobiyama (KEKB) J. Fox, D. Teytelman, S. Prabhakar(SLAC) J. Seebek (SSRL), G. Strover, J. Byrd (LBNL) Thank You for Your Attention ! BIW06, FNAL, May 1~4, 2006

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