1. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Breakout Session: Controls Physics Requirements Overview P. Krejcik

2. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Key accelerator physics factors driving controls design Precision beams low emittance, short bunch lengths Stringent stability requirements Feedback control of orbit, charge energy and bunch length Single pass beams unlike storage ring, every pulse potentially different Precision timing requirements

3. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Key facility factors driving controls design Undulator machine protection Single pulse abort capability Compatibility with non-LCLS beams Straight through beams some months of the year Hybridize new controls with old SLC controls

4. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Design solutions for specialized diagnostics Low emittance beams require Precision wire scanners Average projected emittance Almost non-invasive diagnostic Profile monitor Single pulse full beam profile OTR screens inhibit sase operation Low energy injector beams require YAG screens Slice emittance reconstruction Transverse RF deflecting cavity with profile monitor

5. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Design solutions for specialized diagnostics Short bunch, high peak current beams require Longitudinal bunch profile measurement with sub-picosecond resolution Transverse RF deflecting cavity Electro optic bunch length measurement A non-invasive bunch length monitoring system for pulse-to pulse feedback control Spectral power detectors for CSR and CDR A detector sensitive to micro-bunch instabilities CSR spectrum

6. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Bunch length diagnostic comparison Device TypeInvasive measurement Single shot measurement Abs. or rel. measurement Timing measurement Detect  bunching RF Transverse Deflecting Cavity Yes: Steal 3 pulses No: 3 pulsesAbsoluteNo Coherent Radiation Spectral power No for CSR Yes for CTR YesRelativeNoYes Coherent Radiation Autocorrelation No for CSR Yes for CTR NoAbsolute (2 nd moment only) No Electro Optic Sampling NoYesAbsoluteYesNo Energy Wake-loss YesNoRelativeNo

7. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Feedback global requirements Description of feedback types and locations Orbit charge energy bunch length Control system response time 120 Hz single pulse data transfer, zero latency

8. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 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

9. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Antidamp Damp Gain bandwidth for different loop delays - L. Hendrickson Closed Loop Response of Orbit Feedback

10. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Beam Position Monitoring requirements

11. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Beam Position Monitoring requirements

12. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Linac type stripline BPMs LCLS range Resolution achievable with existing processor New BPM processor design challenges: large dynamic range Low noise, high gain 20 ps timing jitter limit

13. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Cavity beam position monitors in the undulator and LTU Coordinate measuring machine verification of cavity interior X-band cavity shown Dipole-mode couplers X-band cavity shown Dipole-mode couplers Raw digitizer records from beam measurements at ATF R&D at SLAC – S. Smith

14. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Assembled X-band cavity BPM Mechanical center of RF BPM well correlated to electrical center – more accurately than for stripline BPMS

15. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Preliminary beam calibration data from a C-band cavity tested at ATF cavity BPM signal versus predicted position bunch charge 1.6 nC cavity BPM signal versus predicted position bunch charge 1.6 nC plot of residual deviation from linear response << 1  m LCLS resolution requirement plot of residual deviation from linear response << 1  m LCLS resolution requirement 25  m 200 nm R&D at SLAC – S. Smith

16. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Bunch Length Measurements with the RF Transverse Deflecting Cavity   y y  Asymmetric parabola indicates incoming tilt to beam Cavity on Cavity off Cavity on - 180° Bunch length reconstruction Measure streak at 3 different phases  z = 90  m (Streak size) 2 2.4 m 30 MW

17. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Calibration scan for RF transverse deflecting cavity Beam centroid [pixels] Cavity phase [deg. S-Band] Bunch lenght calibrated in units of the wavelength of the S-band RF Further requirements for LCLS: High resolution OTR screen Wide angle, linear view optics

18. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 OTR Profile Monitor in combination with RF Transverse Deflecting Cavity Simulated digitized video image Injector DL1 beam line is shown Best resolution for slice energy spread measurement would be in adjacent spectrometer beam line.

19. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 400 GHz 1.2 mm BC1 Bunch Length Monitor CSR Power spectral density signal for bunch length feedback Spectral lines accompanying micro-bunching instability – Z. Huang. Spectral lines accompanying micro-bunching instability – Z. Huang.

20. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 4 THz BC2 Bunch length monitor spectrum BC2 bunch length feedback requires THz CSR detector Demonstrated with CTR at SPPS

21. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Dither feedback control of bunch length minimization - L. Hendrickson Dither time steps of 10 seconds Bunch length monitor response Feedback correction signal Linac phase “ping” optimum Jitter in bunch length signal over 10 seconds ~10% rms

22. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Timing system requirements Synchronization of fiducials in low-level RF with distribution of triggers in the control system 1/360 s Linac 476 MHz Main Drive Line Sector feed Fiducial detector Master Pattern Generator SLC Control System Event Generator 360 Hz Triggers 8.4 ns±10 ps 128-bit word beam codes 119 MHz 360 Hz fiducials phase locked to low level RF

23. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 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

24. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Controls Issues for Power Supplies 16 types out of a total of 55 power supplies Tightest regulation tolerance is 5*10 -5 (BC’s) transductor regulation circuit Able to use commercial supplies, with SLAC engineering effort for: AC interlocks regulator circuits control interface

25. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Controls Issues for Power Supplies A few unique power supplies: Parallel supplies for linac quads to switch between LCLS operation at low current and HEP operation at full field. Single Bunch Beam Dumper (SBBD) is a 120 Hz pulsed magnet supply Fast orbit feedback requires power supplies and corrector magnets to respond in <8 ms (120 Hz).

26. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 MPS - Beam Rate Limiting Single bunch beam dumper (SBBD) Linac beam up to the dog-leg bend in the LTU can be maintained at 120 Hz Favorable for upstream stability and feedback operation Pulsed magnet allows Single shot, 1 Hz, 10 Hz, 120 Hz down the LTU line Failure in pulsed magnet will turn off beam at gun Tune-up dump at end of LTU Max. 10 Hz to tune-up dump Stopper out will arm MPS for stopping beam with the SBBD

27. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 MPS - Beam Rate Limiting Conditions that will stop the beam at the SBBD Tune-up dump at end of LTU is out, and: Beam loss at detected by either by PLIC along the undulator chamber, or by the PIC’s between the undulator modules Invalid readings from undulator Vacuum Magnet movers BPMs Energy error in the LTU PIC’s at the collimators Launch orbit feedback failing Magnet power supplies for some key elements

28. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 end

29. Patrick Krejcik LCLS FACpkr@slac.stanford.edu April 29, 2004 Jitter determination from Electro Optic sampling ErEr Principal of temporal-spatial correlation Line image camera polarizer analyzer EO xtal  seconds, 300 pulses:  z = 530 fs ± 56 fs rms  t = 300 fs rms single pulse A. Cavalieri centroid width