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Breakout Session: Controls

Breakout Session: Controls. Physics Requirements and Technology Choices for LCLS Instrumentation & Controls. Accelerator Physics Driving Controls Design. Precision beams Low emittance Short bunch. Single pass Every shot different. Compatibility Other programs Old controls.

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Breakout Session: Controls

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  1. Breakout Session: Controls Physics Requirements and Technology Choices for LCLS Instrumentation & Controls

  2. Accelerator Physics Driving Controls Design • Precision beams • Low emittance • Short bunch Single pass Every shot different • Compatibility • Other programs • Old controls • Timing distribution • RF Phase control Simultaneous Single shot Read all devices PS control Process/respond in < 1/120th sec. • Feedback • Trajectory • Bunch length • Energy • Applications • Machine tuning

  3. Critical design choices for instrumentation • Power supply control and regulation • Stability and latency time for fast feedback control • Beam position monitor signal processing • Resolution, drift, calibration • Timing distribution • Precision, stability, synchronization, SLC compatibility • RF stabilization • Beam based feedback • Single-shot CSR bunch length monitors

  4. Power supply system requirements • Stability requirements • 10 ppm in the chicane bends • Response time • Low control-system latency for feedback • <1 ms • Commercial components • Reliability

  5. Digital PS controller developed by SLS • PWM digital regulation loop controls AC converter power module • PWM is a digital process already • Avoids unnecessary digital => analog => digital conversion • Only source of drift in an all digital system is ADC reference voltage • High-speed links, minimal latency • Fully developed at SLS with proven performance • Fully integrated into EPICS controls • Now adopted by several large accelerator projects, including Diamond Light Source

  6. Power supply controller system layout EPICS I O C 8 ch VME card ADCCard Power Supply DSP Controller 5MHz Optical fiber PWM signal Monitor signals DCCT load PWM AC Converter AC line

  7. Courtesy F. Jenni, PSI

  8. PSI Digital Power Supplies Master Fast Optical Link (5 MHz) DSP Controller ADC/DAC Card Optical Trigger 0..6 Slaves PWM Signal I DIO U1..4 DCCT Magnet Power Converter Courtesy A. Luedeke, PSI

  9. Enhancements to the SLS PS Design • Diamond Light Source exploits the following capabilities of the SLS system • Works with any PWM power converter • so use commercial units (OCEM, Bruker) • One controller can drive multiple, load-sharing AC converter power modules • So use multiples of standard units to customize, e.g. 4 x 25 A modules for one 100 A supply • Add an extra module to take up load if one fails • Modules are hot-swappable • Reliability, with minimal downtime from PS

  10. Beam Position Monitoring requirements

  11. Beam Position Monitors • Stripline BPMs in the injector and linac (existing) and in the LTU • Differencing large numbers • Mechanical precision • Fabrication by printing electrodes on ceramic tubes • Drift in electronics • Digital signal processing • Cavity BPMs in the undulator, LTU launch • Signal inherently zero at geometric center • C-band (inexpensive) signal needs to be mixed down in the tunnel

  12. P l/4 Stripline f Digital processing ADC x4 700 MHz Control system RF in l 500 MHz BP filter 119 MHz Clock 24th harmonic C-band cavity Mixer IF ~5 GHz Dipole mode coupler LO sync’ed to RF Stripline versus Cavity BPM Signals • noise (resolution) minimized by removing analog devices in front of ADC that cause attenuation • drift minimized by removing active devices in front of ADC

  13. Simplistic View of Digital BPMs • Is the purely digital approach the best way to go? • Must always maximize signal to noise for best resolution • So minimize any cause of attenuation: couplers, hybrids, active devices etc. • This also eliminates drift which causes offsets • Other approaches also try to do this: e.g. AM to PM conversion with a hybrid and then digitize • Might as well digitize first, eliminate the middle men, and do the conversions digitally • Ultimately left with calibrating the drift in the BPM cables, because ADCs are now very stable.

  14. Linac stripline BPMs • Need to replace old BPM electronics • Commercially available processing units look promising • Beam testing of module (on order) can begin soon http://www.i-tech.si

  15. Analysis of Test Signals in the “Libera” module – S. Smith • Measured signal to noise ratio implies resolution of 7 mm in a 10 mm radius BPM • Identified fixable artifacts in data processing

  16. Pros and Cons of the Libera concept • Complete, integrated commercial package which comes close to requirements • RF processing, digitization, calibration, control software and feedback DSP all in one box • Makes it hard for us get inside and tweak it • Access to fast signals for feedback systems • Difficult to provide timestamps and interrupts in their O/S • Might be better to separate out the functions into different modules

  17. Fabricating a Digital BPM processor out of commercially available modules – Till Straumann • RF filter, local oscillator and mixer stage • VME based ADC board • e.g. Joerger, Echotek handle 8 channels • IOC • Calculates signal amplitude & beam position, tmit. • interfaces to EPICS, • procedures for calibration, • process feedback algorithm

  18. Signal losses in long BPM cables versus placing electronics in the tunnel • We are choosing a high frequency component of the BPM signal to maximize amplitude • But this is rapidly attenuated in long cable runs • Can down-convert next to the BPM with a local oscillator and a mixer • Unacceptable to put electronics in the linac tunnel, • pay for better cables • But may be acceptable to put down-converter electronics in the undulator and LTU tunnels • Highest resolution required there

  19. Timing system requirements • Synchronization of fiducials in low-level RF with distribution of triggers in the control system 360 Hz fiducials phase locked to low level RF 1/360 s Linac 476 MHz Main Drive Line Sector feed Fiducial detector SLC Control System 119 MHz Event Generator 360 Hz Triggers 8.4 ns±10 ps Master Pattern Generator 128-bit word beam codes

  20. 8.4 ns 16 bit word 8.4 ns 8.4 ns Digital distribution of SLAC timing • Technology developed at SLS • Commercialized, refined, adopted at Diamond 10 GBit ethernet hardware but not ethernet protocol. Event generator EVG VME module RF master oscillator 476 MHz MDL Divide by 4 Fiducial detector Clock 119 MHz FPGA fiber Event receiver EVR VME module Fan out 8 ch Triggers 3 ps stability fiber Optional vernier module

  21. 3 Levels in the Timing System • “coarse” triggers at 360 Hz with 8.4 ns delay step size and 10 ps jitter • Gated data acquisition (BPMs) • Pulsed devices (klystrons) • Phase lock of the low-level RF 0.05 S-band (50 fs) phase stability • Timing measurement of the pump-probe laser w.r.t. electron beam in the undulator 10 fs resolution

  22. X- X-band LCLS Machine Stability Tolerance Budget From P. Emma: RMS tolerance budget for <12% rms peak-current jitter or <0.1% rms final e− energy jitter. All tolerances are rms levels and the voltage and phase tolerances per klystron for L2 and L3 are Nk larger, assuming uncorrelated errors, where Nk is the number of klystrons per linac. 125 fs tolerance on X-band system

  23. E E E Φrf(L2) Φrf(L3) Vrf(L1) DL1 sz Φrf(L1) sz E Φrf(L2) Vrf(L0) DL1 Spectr. BSY 50B1 BC2 BC1 DL2 L1 L2 L3 L0 Energy and Bunch Length Feedback Loops • Beam based feedback will stabilize RF F,A • Against drift and jitter up to ~10 Hz • But no diagnostic to distinguish drift of X-band • Linearization, higher-harmonic RF has the tightest tolerance • No unique beam measurement

  24. CSR Single-shot Bunch Length Detector • Off-axis synchrotron radiation • Reflected through a port to: • Fixed BW detector • Autocorrelator • Prototype at SPPS THz power detector Bunch Compressor Chicane THz autocorrelator B4 Bend CSR Vacuum port with reflecting foil

  25. End of presentation! Additional backup material follows

  26. Linac type stripline BPMs • New BPM processor design challenges: • large dynamic range • Low noise, high gain • 20 ps timing jitter limit Resolution achievable with existing processor LCLS range

  27. Cavity beam position monitors for the undulator and LTU R&D at SLAC – S. Smith Coordinate measuring machine verification of cavity interior • X-band cavity shown • Dipole-mode couplers • X-band cavity shown • Dipole-mode couplers NLC studies of cavity BPMs, S. Smith et al

  28. C-band beam tests of the cavity BPM – S. Smith cavity BPM signal versus predicted position at bunch charge 1.6 nC 25 mm • Raw digitizer records from beam measurements at ATF 200 nm • plot of residual deviation from linear response • << 1 mm LCLS resolution requirement • C-band chosen for compatibility with wireless communications technology

  29. Jitter in the laser timing effects Electro optic bunch timing measurement Pump-probe timing for the users Enhancement schemes using short pulse lasers Synchronization of the Laser timing

  30. SPPS Laser Phase Noise Measurements – R. Akre 476 MHz M.O. fiber ~1 km MDL 3 km Ti:Sa laser osc EO VCO diode 2856 MHz x6 Phase detector 2856 MHz to linac scope

  31. Single-Shot Bunch length scan <300 fs Timing Jitter 170 fs rms Electro-Optical Sampling at SPPS – A. Cavalieri et al. EO crystal Line image camera Pol. Laser pulse analyzer polarizer Er Electron bunch

  32. Closed Loop Response of Orbit Feedback Antidamp Damp Gain bandwidth for different loop delays - L. Hendrickson

  33. Control of Digital Power Supplies Andreas Lüdeke Swiss Light Source / PSI 20 May 2003 EPICS Collaboration Meeting

  34. PSI Digital Power Supplies Andreas Lüdeke Master Fast Optical Link (5 MHz) DSP Controller ADC/DAC Card Optical Trigger 0..6 Slaves PWM Signal I DIO U1..4 DCCT Magnet Power Converter

  35. Why use Digital Power Supplies? Andreas Lüdeke • Single source of drifts: ADC voltage reference • All PS at the SLS proved to have excellent stability • Flexibility of the power supplies • Regulation loop can be adapted to load • Easy to add new power supply features on DSP • Good reproducibility, reliability • PWM is digital, modern DCCT will be digital • Why not?

  36. Hardware Overview Andreas Lüdeke • Parallel fast access • (10k frames per sec) • IOC  IP • DSP  IP • … Power Supply Controller VME Trans.Mod. T.Mod Orbit DSP IP IP IP IP Linux PC Consoles IOC Carrier EVR Timing

  37. Power Supply Hardware Andreas Lüdeke • DSP Controller Card • Euro card size • Shark DSP • Shark links on backplane • ADC/DAC card • 2 ADC, 16 Bit, 50 kHz • 4 ADC, 12 Bit • 2 DAC for debugging

  38. Fast and precise ADC Andreas Lüdeke UADC [V] 10 µV 1 ppm 20th Bit Umax 4.7895 4.7894 - 10 µV + 20 µV 4.7893 1 kHz Filter 600 µV 4.7892 - 10 µV - 40 µV 4.7891 4.789 Umin 4.7889 4.7888 0 200 400 600 800 1000 1200 1400 1600 1800 2000 33 min t [s]

  39. VME Hardware Andreas Lüdeke • Industry Pack Carrier • VME64x 4 slot boards • “off-the-shelf”: • Greenspring • Vipc664 • Hytec 8002 Industry Pack Module for 2 power supplies VME64x Transition module for 8 power supplies

  40. DSP Software Andreas Lüdeke • Local intelligence: • 50 kHz pulse width modulation loop • Sophisticated alarms, like change in load resistance • Triggered current waveform (DSP ramp) • Scaleable, arbitrary waveform • 16000 times 80 µsec steps  > 1 second waveform • The same DSP program for all PS • Locally stored parameter settings for each PS

  41. EPICS device/driver Andreas Lüdeke • Carrier board independent by use of drvIpac • Read and write 256 power supply registers • DSP waveform and program downloads • Softramps: synchronised current waveforms • Arbitrary clock rate (<1kHz) for 8000 setpoints • Synchronised by timing system • Diagnostic records • Statistics of optical fibre link and IP failures

  42. EPICS database Andreas Lüdeke • One template for 500 power supplies • Each power supply supports • Download and save of DSP programs, parameter sets, DSP ID • current waveform: download, scaling, offset, length, … • reading max. and min. current from PS • reading actual magnet resistance from controller • ... • Magnet cycling configurable for each PS • Detailed fault diagnostic for PS, link and driver

  43. Software Management Andreas Lüdeke • DSP software is documented by Excel sheets • Script transforms sheets into a C include file • Easy upgrade of the driver for new PS functions • Identical DSP and EPICS software for all PS • Configuration by parameter set

  44. Outlook Andreas Lüdeke • PSI type digital PS are “en vogue” • Each manufacturer can get a PSI licence • Diamond will use exclusively digital PS for magnets • Soleil is evaluating the PSI digital PS • Industry Pack module can be used on CPCI • Driver source can be reused for Tango • Customized DSP programs • For specific application • To drive several PS with one DSP card

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