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SLS D igital B eam P osition M onitoring S ystem

SLS D igital B eam P osition M onitoring S ystem. Care-N3-ABE Networking Workshop June 2004. System overview System elements Run modes Problems and solutions? Future developements. Outlines. BPMs in SLS Accelerators - linac / linac to booster transfer line: 6 BPMs

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SLS D igital B eam P osition M onitoring S ystem

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  1. SLS Digital Beam Position Monitoring System Care-N3-ABE Networking Workshop June 2004 • System overview • System elements • Run modes • Problems and solutions? • Future developements Outlines

  2. BPMs in SLS Accelerators - linac / linac to booster transfer line: 6 BPMs - booster: 54 BPMs - tune BPM in booster: 1 BPM - booster to storage ring transfer line: 3 BPMs - storage ring: 72 BPMs - tune BPM in storage ring: 1 BPM Total Number of BPMs: 137 BPMs Strategy Use one type of BPM electronics for all sections of the machine Digital BPM System with reprogrammable digital down converters

  3. Development • Collaboration between • ELETTRA (Trieste, Italy) • SLS • R. Uršič (Consultant) • Concept • 4 channel system • modular system (VME technology ) • - RF front end • (down conversion to IF) • - Quad Digital Receiver • (digital down conversion to base band) • - Digital Signal Processing (position calculation) • pilot signal in all four channels • → calibration of electronics by individual gain settings

  4. June 1998: Concept and proposal. October 1998: Start evaluation of commercials digital receiver systems and in parallel start developement studies for a custom solution. January 1999: Decision for custom developement. July 1999: First prototype works @ Elettra, proof of principle. June 2000: SLS linac & transfer lines commissioning with DBPM serie 1.0. August 2000: SLS booster commissionning with DPBM serie 1.1. December 2000: SLS Storage ring commissionning with DBPM serie 1.2. No significant hardware changes made since january 2001 !!! Development Milestones

  5. Hardware modularity Quad Digital Receiver DSP RF Frontend

  6. Turn by Turn / pulsed mode / tune mode Positions of 8192 turns available after trigger event from timing system, batch processing done by DSP. Closed orbit / feedback mode DDC samples available at DDC output rate, real time position processing done by DSP. Position average and RMS calculation for operators display and archiving. Ramp mode(booster mode) Similar to turn by turn mode, with reduced data rate (higher decimation) in order to provide beam position through-out the acceleration cycle. Operating modes

  7. Resolution gain ranges (80% filling pattern)

  8. Stability long term stability measurement in technical gallery (with RF signal generator): <2 mm *) <2.5 mm *) *) hall temperature (technical gallery) regulated < ±1 ºC (spec)

  9. Stability (2): Lab Measurements • due to hot summer 2003: “relaxed” setting in cooling • system • air conditioning system • in lab shows a strong 2 ºC • swing now • “small” temperature • reservoir in lab compared • to technical gallery hall upgrade plans: measure air temperature at BPM crates and correct for systematic temperature effects

  10. Beam Current Dependency • top-up operation minimal influence • of beam current • dependency • orbit correction only for Ibeam > 20 mA

  11. Booster Ramp Booster current: ~5 mA Booster current: ~0.5 mA Intensity horizontal position vertical position injection booster extr. injection

  12. Numerical Controlled Oscillator Frequency Tracking • main RF frequency changes • (→ orbit correction) • fixed LO frequencies in RF front ends • (DBPM1) • DBPM closed orbit mode → 200 Hz passband bandwidth track main RF frequency on DBPM by reprogramming the digital receivers (automated in EPICS control system)

  13. Local Oscillator Frequency drifts in RF Front Ends • drift of LO freq. • correlated with • techn. gallery air • temperature • small passband • bandwidth of BPM • in closed orbit mode • require weekly • measurements of • LO frequencies DBPM system will profit from planned cooling system upgrades

  14. Systematic Effects Sector Layout: • slow feedback on X-BPM changes reference for fast orbit feedback • photon beam position kept constant with asymmetric bump • observation: • slow drift related to temperature changes of DBPM RF front end • 40-50 min period due to filling pattern dependence of DBPM

  15. Systematic Effects (cont’d) • implementation of filling pattern feedback compensates • 40-50 min period • remaining: temperature dependence of RF front end upgrade plans: temperature calibration with lookup tables

  16. DBPM was available on time. System fulfills the specifications System flexibility contributed to the success of the SLS commissioning Excellent orbit reproducibility Availability of the DBPM system is vital for the SLS operation Systematic effects in the order of the system resolution , mainly due to the analog part of the system (RF – Frontend) Still plenty of room for improvements Higher ADC resolution Local oscillator frequency tracking Temperature compensation by software Conclusion

  17. The future … • VPC Generic PMC carrier Board.

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