1. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Breakout Session: Controls Physics Requirements and Technology Choices for LCLS Instrumentation & Controls

2. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Outline Beam position monitors Issues for the undulator cavity BPMs Issues for signal processing Power supplies and controllers Pulsed operation of DL1 for diagnostics Low level RF Source and synchronization issues Feedback and x-band regulation Bunch length monitors

3. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Cavity Beam Position Monitors Frequency choice Cavity Iris should be masked from SR Vacuum chamber dimensions for the undulator are now chosen 12 mm aperture is close to X-band cutoff Evaluating two frequency choices (Z. Li) Issues BPM location with respect to quadrupoles Resolution in combination with beam-based alignment with EM quads Signal processing 5 mm 10 mm

4. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Undulator Cavity BPM locations with respect to quadrupoles Quadrupole and BPM mounted adjacent on the undulator support cradle to ensure 1 um beam based alignment resolution Also need to keep the distance between the electron beam and the undulator segment axis to less than 70 microns rms Considering beam position measurement options at downstream end as well Train-linked undulator sections – see H.-D. Nuhn presentation Quad BPM assemblies Optional wire monitors,

5. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Cavity BPM Signal Processing X and Y cavity at each undulator plus ~1 phase reference cavity per girder High-frequency x-band signal is attenuated in a short distance Incorporate a local mixer to IF at the cavity Only a simple passive device in the tunnel Temperature stable Relatively low radiation loss environment Distribution of reference x-band oscillator signal in the tunnel Choose intermediate frequency to match into the RF front end used for stripline

6. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Digital BPM Signal Processing Use same RF front end for stripline BPMs and output from first mixer for cavity BPMs Initial desire to use a commercially produced BPM processing module (Libera) We obtained a try out Libera module Integration into the control system not proceeding fast enough, e.g. could not access raw data in the module. Present design solution Commercial VME 8 channel digitizer RF front end from discrete, commercial components

7. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Power supplies and controllers Requirements Stability of 1E-5 for bunch compressors fast response for feedback correctors Integrate with epics controls reliability Design solution digital controller/regulator developed at PSI and further developed at Diamond commercially supplied power modules

8. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Power supplies and controllers Status Test power supply delivered from PSI controlled from an epics IOC long term current stability tests into resistive load are underway

9. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 PSI Power Supply 12 hour Test <2.5E-5

10. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Pulsed operation of DL1 for diagnostics Propose to allow option of pulsing DL1 bends allow pulse stealing at ~1 Hz into the spectrometer line monitor beam profile and energy spread Potentially combine with pulsing of the transverse cavity Propose to allow option of pulsing DL1 bends allow pulse stealing at ~1 Hz into the spectrometer line monitor beam profile and energy spread Potentially combine with pulsing of the transverse cavity Laminated magnet Experience at SLAC with damping ring DRIP magnets Keep two dipoles in series Need to maintain 1E-4 stability Laminated magnet Experience at SLAC with damping ring DRIP magnets Keep two dipoles in series Need to maintain 1E-4 stability Laminate magnets now Develop pulsed supply later Laminate magnets now Develop pulsed supply later

11. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Pulsed operation of DL1 for diagnostics 1 Hz pulsed into the spectrometer line monitor beam profile monitor energy spread Investigate further if transverse cavity can be optimized for slice measurements in the spectrometer line

12. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Low Level RF Feedback and x-band regulation Question that arose last time was how to distinguish drift in the X-band system from errors in the S-band system Solution is to keep X-band regulation fixed, and compensate errors with the S-band system only See next slide Source and synchronization issues noise and stability issues in oscillator and distribution

13. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Demonstration of L1 S-band adjustment to compensate Lx errors – courtesey Juhao Wu X-band phase error of + 5 o, fixed with L1 S-band adjustment: phase +2.1°, voltage - 2.1 % X-band amplitude error of 5 %, fixed with L1 S-band adjustment: phase +0.61°, voltage 0.18 %

14. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Low Level RF Source and synchronization Present design concept: Microwave crystal oscillator phase locked to SLAC MDL – low noise in the low frequency band Gun laser oscillator mode locked to crystal oscillator – low noise in the high frequency band Under evaluation Derive the LLRF 2856 MHz from crystal oscillator or from laser optical output Distribute LLRF over copper or optional optical fiber

15. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 RF/Laser distribution proposed by Ilday et al, MIT at the SLAC Timing workshop Master laser oscillator Low noise crystal microwave oscillator Upgrade path: Fiber distribution system RF-optical synchronization module LLRF to klystron Optical-laser synchronization module Baseline Cu Coax distribution Linac MDL

16. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 RF stabilization – Ilday et al, MIT

17. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Derivation of LLRF from laser – F. Omer Ilday, MIT

18. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Synchronizing Gun and User Lasers – F. Omer Ilday, MIT

19. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Non-intercepting detector for off-axis synchrotron radiation Reflected through a port to: Spectral Power detector Single shot Autocorrelator BC1, BC2 Single-shot Bunch Length Detectors THz autocorrelator THz power detector B4 Bend Bunch Compressor Chicane CSR Vacuum port with reflecting foil

20. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 The CSR we now understand is dominated by Coherent Edge Radiation Same spectral and angular distribution characteristics as transition radiation Need to account for interference effects from adjacent magnets Experimental investigation at SPPS planned Can also learn from UCLA expt at BNL-ATF Bunch Length Monitor Issues

21. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Need practical experience in evaluating window materials Detectors (pyrometers, Golay cells, bolometers) Autocorrelator designs (mirrors, splitters, detectors) New development of single-shot autocorrelators Bunch Length Monitor Issues

22. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 End of Presentation Backup slides

23. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Power supply controller system layout IOCIOC EPICS Power Supply DSP Controller ADC Card PWM AC Converter load DCCT 8 ch VME card AC line 5MHz Optical fiber PWM signal Monitor signals

24. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 PSI Digital Power Supplies ADC/DAC Card DSP Controller DCCT 0..6 Slaves Magnet PWM Signal Fast Optical Link (5 MHz) DIO U 1..4 I Power Converter Master Optical Trigger Courtesy A. Luedeke, PSI

25. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Stripline versus Cavity BPM Signals P f 700 MHz 500 MHz BP filter ADC x4 119 MHz Clock 24 th harmonic Digital processing RF in Control system /4 Stripline Mixer LO sync’ed to RF IF noise (resolution) minimized by removing analog devices in front of ADC that cause attenuation drift minimized by removing active devices in front of ADC noise (resolution) minimized by removing analog devices in front of ADC that cause attenuation drift minimized by removing active devices in front of ADC C-band cavity Dipole mode coupler ~5 GHz

26. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 SPPS Laser Phase Noise Measurements – R. Akre 476 MHz M.O. x6 2856 MHz to linac MDL 3 km fiber ~1 km VCO Ti:Sa laser osc diode EO scope Phase detector 2856 MHz

27. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Courtesy F. Jenni, PSI

28. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 7-8, 2005 Beam based feedback will stabilize RF  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 Energy and Bunch Length Feedback Loops L0 L1 DL1 Spectr. BC1 BC2 L2L3 BSY 50B1 DL2 V rf (L0) Φ rf (L2) V rf (L1) Φ rf (L3) EEE Φ rf (L2) zz Φ rf (L1) zz E