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Diagnostics (WBS 1.5) Yiping Feng

Diagnostics (WBS 1.5) Yiping Feng. Motivations System Specifications System Description WBS Schedule and Costs Summary. Motivations. X-ray Free-Electron Laser (FEL) is fundamentally different from storage-ring based synchrotron sources Linac-based, single-pass, 120 Hz at LCLS

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Diagnostics (WBS 1.5) Yiping Feng

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

  2. 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

  3. 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

  4. Expected Fluctuations of LCLS FEL pulses *To be discussed in details in breakout session

  5. X-ray Diagnostics Suite

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

  7. 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

  8. 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

  9. 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;

  10. 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;

  11. 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

  12. 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

  13. 1.5 WBS

  14. Diagnostics Schedule in Primavera 3.1

  15. Diagnostics Milestones CD-1 Aug 01, 07 Conceptual Design Complete Oct 24, 07 CD-2a Dec 03, 07 CD-3a Jul 21, 08 Phase I Final Design Complete Oct 24, 07 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

  16. Diagnostics Cost Estimate

  17. 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 sciences 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

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