Diagnostics (WBS 1.5) Yiping Feng

1. Diagnostics(WBS 1.5)Yiping Feng • System Specifications • System Description • Technical Challenges • WBS • Schedule and Costs • Summary

2. Expected Fluctuations of LCLS FEL pulses *Discussed in Breakout Summary Session

3. X-ray Diagnostics Suite

4. System Specifications Technically more challenging * Must have high damage threshold

5. Quantities of Diagnostics Diagnostics Station Standardized and Modularized

6. XPP CXI XCS Placement of Diagnostics XPP (EO in LTU) CXI XCS

7. Detailed Placement in XPP

8. Pop-In Intensity Monitor (WBS 1.5.3) • Coarse alignment of X-ray optics • monochromators, mirrors, lens, etc. • strategically placed in close proximity to optic • Detection technique • Pulse operation not photon counting • Sensor type • Si Diode (used successfully at SPPS) • CVD Diamond stages FEL Destructive; Retractable; Moderate dynamic range 104; Relative accuracy < 10-2; Per-pulse operation at 120 Hz; Si Diode

9. Pop-In Position/Profile Monitor (WBS 1.5.2) • Coarse alignment of X-ray optics (beam finder) • Optical imaging of fluorescence from a scintillating screen • Positions in x, y • 2D intensity profile • Attenuation of beam may be required to avoid saturation • Two modes of operation: low and high resolutions stages CCD Camera Mirror Destructive; Retractable; At 50 mm resolution 25x25 mm2 field of view; At 10 mm resolution 5x5 mm2 field of view; FEL YAG Screen

10. a a a Diagnostic needs: Ultrafast Measurement of Atomic Displacement – an example N=12463 • Precise normalization of incident intensity to 0.1% • Critical to XPP experiments: small changes in diffraction intensity need to be resolved • Relative timing btw e-bunch & EOS-probe laser pulse - Inferring timing btw X-ray pulse & experimental probe laser D. M. Fritz et al., Science315, 633 (2007)

11. In-Situ Intensity/Position Monitor (WBS 1.5.4) Quad-sensor • Precise normalization of incident intensity to 0.1% • Critical to XPP experiments where small change in diffraction intensity need to be resolved, i.e. Bi coherent phonon decay after photo-excitation • Detection technique • Compton back scattering from Be thin foil (up to 108photons w/ 1012 in incident beam) • Precise beam position calibration w/ use of array of sensors to < 5 mm • Commercial fluorescence monitor using similar design provides equal resolution but not viable due to damage considerations • CVD diamond design more complex in fabrication FEL Be thin foil Transmissive (> 98% w/ 100 mm Be @ 8 keV); High dynamic range 106; Relative accuracy < 10-3 Position resolution < 5 mm; Per-pulse operation at 120 Hz;

12. In-Situ Intensity/Position Monitor Si Diode Used at SPPS 2 mm Single photon 10^4 range 400 mm thick Pulse Detection Circuitry

13. Laser/FEL Timing Master Clock RF Distribution Network Electron Gun Accelerating Elements Experimental Pump Laser • Sources of short-term jitter • E-beam phase to RF phase jitter • Electron beam energy jitter + dispersive electron optics • End station laser phase to RF Phase locking jitter • Short-term timing resolution ~ 1 ps • Long-term jitter • Length of RF cable thermal variation Timing jitter reduces the visibility of experimental effects

14. Electro-Optic Sampling Device (WBS 1.5.6) • Relative timing btw e-bunch & EOS-probe laser pulse • Inferring timing btw X-ray pulse & experimental probe laser • Based on (linear) Pockels effect • birefringence in strong E-field exerted by relativistic e-bunch in proximity • 1-D Spatial encoding of timing for detection using CCD • Single shot measurement • EOS technique proven at SPPS • 20 fs timing determination • 200 fs resolution for e-bunch length • Challenges • Long distance btw EOS location (LTU) & experiments (NEH) • 120 Hz operation requires real-time processing of EOS data EOS crystal Probe-laser footprint Non-intrusive to e-beam; Non-destructive; Per-pulse operation at 120 Hz;

15. Hub Stabilized Fiber Optic LLRF Distribution Network (< 10 fs) Developed by LBNL fiber link LTU NEH Sector 20 Gun Laser Electro-optic Sampling Laser Pump-probe Laser Enhanced Laser/FEL Timing @ LCLS • Electro-optic Sampling • Enhanced Temporal Resolution (~ 100 fs) • Limited by our ability to phase lock the lasers to the RF backbone • Limited by Intra-bunch SASE jitter

16. Length-Stabilized Fiber Network

17. Hartmann Wave-front Sensor (WBS 1.5.5) • Characterization of wave-front of focused X-ray FEL is a challenge • Critical to CXI experiments if atomic resolution is ultimately to be achieved • Common scanning or direct imaging techniques made at focus not viable due to FEL high peak power • Hartmann Wave-front Sensor technique is viable • Measurement made far from focus • Focal point determination calculated from radius of curvature measurement • Wave-front distortion obtained by back-propagation of diffracted wave-front determined at mask plane • Commercial Hartmann wave-front for long wavelength • Successful in optical applications (adaptive optics, etc.) • For X-ray applications, X-EUV sensor for energy up to 4 keV • Needs modification for higher energies and 120 Hz operation

18. Hartmann Wave-front Sensor (con’t) • Challenges • Working at 8 keV • Tighter technical specs at shorter wavelength • Mask must allow ray-optics approximation • New 8 keV version being developed & tested now • Mask materials must be compatible with FEL application • 120 Hz operation will require customization • Imaging sensor readout rate not sufficient • Use pixelated detector capable of 120 Hz operation • Integrate with Controls/Data systems Divergent wavefront Algorithm Image obtained from Imagine Optics, Ltd

19. Hartmann Wavefront Sensor Hartmann Plate 2D Detector Focusing Optic Focal Plane W FEL Beam w0 f D L *Requires a defocusing optic

20. Diffractive Wavefront Reconstruction • The oversampled diffraction pattern of the focus is measured. • The focal spot is iteratively reconstructed by propagating the wave from the optic to the focus and then to the detector plane. • The constraints are applied at the optic and detector planes. Attenuator 2D Detector Focal Plane Focusing Optic W FEL Beam w0 f L

21. Diffractive Imaging Nature Physics Vol 2. p101

22. 1.5 WBS

23. Diagnostics Schedule in Primavera 3.1

24. Diagnostics Milestones CD-1 Aug 01, 07 Conceptual Design Complete Oct 24, 07 CD-2a Dec 03, 07 CD-3a Jul 21, 08 EOS monitor complete Oct 20, 08 Pop-in position/profiler 1st article Nov 25, 08 In-situ intensity/position 1st article Jan 21, 09 Pop-in intensity 1st article Apr 15, 09 Phase I Installation Complete Aug 21, 09 CD-4a Feb 08, 10

25. Diagnostics Cost Estimate

26. 1.5 Level 3 Costs (M$)

27. WBS 1.5 - Diagnostics • Cost estimate at level 3 by fiscal year –

28. Summary • Concepts of all diagnostic devices are well developed • Frequent design discussions amongst LUSI and LCLS scientists • EOS device was successfully deployed at SPPS • 1st articles will help LCLS commissioning/operation and early science on LUSI instruments • LUSI EOS will aid LCLS e-beam diagnostics • LUSI BPM could aid LCLS e-beam fast feedback system • Ready to proceed with baseline cost and schedule development

30. FEL Source Propagation A diffraction limited Gaussian source is assumed

31. CVD Diamond BPM CVD Diamond BPM

32. Motivations • X-ray Free-Electron Laser (FEL) is fundamentally different from storage-ring based synchrotron sources • Linac-based, single-pass, 120 Hz at LCLS • Feedback is limited by low repetition rate • Each macro electron bunch is different in timing, length, density, energy (velocity), orbit, etc. • X-ray amplification process based on self-seeding SASE* • Lasing starts from a random electron density distribution • Each X-ray pulse consists of a random time sequence of spikes of varying degrees of saturation • X-ray FEL exhibits inherent Intensity, spatial, temporal, and spectral fluctuations on pulse by pulse basis *Self Amplification of Spontaneous Emission

33. Goals • X-ray diagnostics are required to measure these fluctuations since they can’t be eliminated • Integral parts of Instruments • Timing & intensity measurements for XPP experiments • Wave-front characterization for CXI experiments • Measurements made on pulse-by-pulse basis • Requiring real-time processing by controls and data system • Commonalities in needs & specs • Standardized and used for all applicable instruments • Modularized for greater flexibility of deployment and placement • Critical diagnostics must be performed and data made available on pulse-by-pulse basis

34. a a a Ultrafast Measurement of Atomic Displacement N=12463 x n(t),x(t) f • Relative timing btw e-bunch & EOS-probe laser pulse • Inferring timing btw X-ray pulse & experimental probe laser

35. Electro-Optic Sampling EO Crystal

36. Spatial Encoding time integrated intensity polarizing beamsplitter time; space time integrated intensity Arrival time and duration of bunch is encoded on profile of laser beam

37. Non-sequential Sampling 100 consecutive shots Single shot, Lorentzian fit

38. Non-sequential Sampling