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Feedback on Nanosecond Timescales (FONT) - Review of Feedback Prototype Tests at ATF(KEK)

Feedback on Nanosecond Timescales (FONT) - Review of Feedback Prototype Tests at ATF(KEK). Glenn Christian John Adams Institute, Oxford for FONT collaboration. ILC IP Feedback system - concept.

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Feedback on Nanosecond Timescales (FONT) - Review of Feedback Prototype Tests at ATF(KEK)

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  1. Feedback on Nanosecond Timescales (FONT)- Review of Feedback Prototype Tests at ATF(KEK) Glenn Christian John Adams Institute, Oxford for FONT collaboration

  2. ILC IP Feedback system - concept • Fast beam-based feedback system essential for the ILC interaction point to compensate for relative beam misalignment. • Measure vertical position of outgoing beam and hence beam-beam kick angle • Use fast amplifier and kicker to correct vertical position of beam incoming to IR • Delay loop necessary to maintain the correction for subsequent bunches in the train Last line of defence against relative beam misalignment Glenn Christian - LC-ABD 24/09/07

  3. Previous Feedback Prototypes • Originally FONT technology demonstrator for ultra-fast feedback, driven by challenge of ‘warm’ machine (192 x 1.4 ns) • very low latency system (analogue only) • FONT@NLCTA – 2001-4, 65 MeV beam, 170 ns train length, 87 ps bunch spacing • FONT1 – latency 67 ns • FONT2 – latency 54 ns • FONT3@ATF - 2004-5, 1.3 GeV beam, 56 ns train length, 2.8 ns bunch spacing • take advantage of ~ GeV beam (1 micron @ 1GeV -> 1 nm @ 1TeV) • latency aim: 20 ns (observe two and a bit periods), 23 ns achieved Glenn Christian - LC-ABD 24/09/07

  4. FONT1,2,3: Summary 67 ns 54 ns 23 ns Glenn Christian - LC-ABD 24/09/07

  5. Current/Future Feedback Prototypes • ‘Cold’-machine bunch parameters allow digital signal processing techniques: • support implementation of algorithms for greater luminosity recovery • easier inter-connectivity of processors – angle feedback? • integration of other systems – upstream feedbacks, feed-forward, lumi-monitor etc. • FONT4@ATF 2005-present, 1-bunch/3-train mode, ~140ns - ~154 ns bunch spacing • demonstrator for digital feedback system with ILC-like bunch spacing • Latency target: < bunch spacing (~140 ns) • Later, • ATF2 – aim to stabilise third bunch @ micron level • (FONT5 ?) 20 – 60 bunches @ 150 – 300 ns spacing (future extraction scheme) Glenn Christian - LC-ABD 24/09/07

  6. FONT4 system overview Witness BPMs Feedback BPM BPM 13 BPM 12 BPM 11 KICKER BEAM Analog FE Analog FE Analog FE AMP ∑ Digital processor ∆ clks, triggers Machine timing system Scopes DAQ LO I/O, digital DAQ Glenn Christian - LC-ABD 24/09/07

  7. Analogue BPM processor Output pulse width c. 5 ns old new Resolution c. 3-5 um Latency c. 10 ns Tested @ ATF November 2006 Glenn Christian - LC-ABD 24/09/07

  8. Digital Board JTAG port PROM Xilinx Virtex4 FPGA 40 MHz oscillator GP I/O Header Analog Devices ADC/DACs (14-bit) RS232 serial port 2 x Analog Output channels (differential or single-ended) 4 x General-purpose digital outputs 2 x Analog Input channels (single-ended) 3 x external clock/trigger inputs Glenn Christian - LC-ABD 24/09/07

  9. Kicker Drive Amplifier New design for “universal” FONT amplifier Designed to have flexibility to meet future requirements Design for 10 us operation with 40 ns settling time to 90%, rep rate up to 10 Hz Output current up to +/- 30 A (kicker shorted), +/- 15 A (50-ohm termination) Manufactured by TMD Technologies Two units delivered 1 December 2006 Tested at ATF Dec 2006 Glenn Christian - LC-ABD 24/09/07

  10. FONT4 installation at ATF (May 2007) Amplifier FEATHER Kicker BPM processor board Glenn Christian - LC-ABD 24/09/07

  11. Recent tests at ATF (May 2007) • Objectives: • Demonstrate closed-loop feedback with full version of firmware • Demonstrate acceptable latency • Optimise feedback gain • Two versions of firmware: • Without charge normalisation • Gain set in software and given as a virtual-input to FPGA in real-time • 5 clock cycles @357 MHz (expected latency ~140 ns) • With real-time charge normalisation • Used a partial reconfiguration technique to recompute LUTs to optimise gain setting • 8 clock cycles @357 MHz (expected latency ~148 ns) • Evaluate the effect of normalisation Glenn Christian - LC-ABD 24/09/07

  12. Latency without charge normalisation (154ns bunch spacing) ~15 ns slack to 90% of full kick Latency ~140 ns Glenn Christian - LC-ABD 24/09/07

  13. Feedback results – no real-time charge normalisation(average over 11 pulses) Glenn Christian - LC-ABD 24/09/07

  14. Feedback results with charge normalisation (average over 11 pulses) Glenn Christian - LC-ABD 24/09/07

  15. Further Development - FONT4 • FONT4 so far concerned with solving technical challenges in getting the closed-loop feedback working. Now, concentrate on quality measurements • Reduce the processor resolution – FOM for system, system resolution • Limited by phase jitter in LO (~ 5 degrees) • Reduce the sensitivity to the LO jitter by balancing the signal levels and better matching of input lengths to the analogue processor – tune the difference signal to zero in the working region of the system • Understand statistical nature of the jitter – correlations? • Requires an integrated, online DAQ system to acquire large data sets and analyse the data in real-time • Step towards making the feedback system ‘turn-key’ at ATF2 Glenn Christian - LC-ABD 24/09/07

  16. Further Developments – ATF2 • Goals/Plans for ATF2: • Resolution 1 micron or less • Need to investigate methods to further improve processor resolution • Defining BPM and kicker locations in beamline and simulate feedback performance • Position and angle feedback in both planes (x,x’,y,y’)? • For position feedback only, could use existing FONT4 processor, but for angle feedback latency increased by physical distance between BPMs, as well as extra clock cycles needed in the processing • New digital board design – two channel, faster ADCs, Virtex-5 FPGA with RocketIO (fast digital interconnects) • Feed-forward and constant-energy extraction (Kalinin) • Same kickers as feedback • Hardware tests at ATF Glenn Christian - LC-ABD 24/09/07

  17. Summary • Completed FONT3 analogue feedback – achieved latency 23 ns • Developed FONT4 digital feedback system • New hardware developed and tested at ATF – analogue and digital processors, amplifier • Demonstrated closed loop feedback at ATF with 3 bunches ~150ns spacing with digital feedback processor • Optimised gain with and without real-time charge normalisation in the system • System latency ~140ns (~148ns with real-time Q-normalisation) • Ongoing programme to further develop system and prepare to employ system at ATF2 Glenn Christian - LC-ABD 24/09/07

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