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Introduction Heinz-Dieter Nuhn, SLAC / LCLS November 14, 2005

Introduction Heinz-Dieter Nuhn, SLAC / LCLS November 14, 2005. Need for Beam Based Undulator K Measurements Review of Beam Based K Measurement Discussions LCLS Undulator Diagnostics Baseline Components LCLS FEL Commissioning Milestones Workshop Objective and Agenda Charge to the Workshop.

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Introduction Heinz-Dieter Nuhn, SLAC / LCLS November 14, 2005

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  1. IntroductionHeinz-Dieter Nuhn, SLAC / LCLSNovember 14, 2005 • Need for Beam Based Undulator K Measurements • Review of Beam Based K Measurement Discussions • LCLS Undulator Diagnostics Baseline Components • LCLS FEL Commissioning Milestones • Workshop Objective and Agenda • Charge to the Workshop 1

  2. Far Hall Undulator Near Hall Linac Coherent Light Source 2

  3. 3

  4. Summary of Nominal Undulator Parameters Undulator Type planar hybrid Magnet Material NdFeB Wiggle Plane horizontal Gap 6.8 mm Period Length 30.0± 0.05 mm Effective On-Axis Field 1.249 T Standard Effective K 3.500 ± 0.015% Range of Effective Undulator Parameter K 3.500 - 3.493 (3.480) Accumulated Segment Phase Error Tolerance 10 degrees(at any point along segment) Module Length 3.40 m Number of Modules 33 Undulator Magnet Length 112.2 m Standard Break Lengths 48.2 - 48.2 - 94.9 cm Nominal Total Device Length 130.954 m Quadrupole Magnet Technology EMQ Nominal Quadrupole Magnet Length 7 cm Integrated Quadrupole Gradient 3.0 T 4

  5. Undulator Segment Prototype 5

  6. Undulator Pole Canting Canting comes from wedged spacers 4.5 mrad cant angle Gap can be adjusted by lateral displacement of wedges 1 mm shift means 4.5 microns in gap, or 8.2 Gauss Beff adjusted to desired value 6

  7. Using Undulator Roll-Away and K Adjustment Function • Horizontal position of undulator segment can be remotely controlled correct Keff on beam axis • This adjustment range goes from fraction of a percent to a complete field turn-off. Neutral; K=3.5000; Dx=+0.0 mm PowerTp; K=3.4804; Dx=+8.5 mm Beam Axis SpontTp; K=3.4929; Dx=+3.0 mm RollAway; K=0.0000; Dx=+100 mm 7

  8. Measurement of Spontaneous Radiation Using Rollout Undulator Segments can be removed by remote control from the end of the undulator. They will not effect radiation produced by earlier segments. 8

  9. Insufficient Knowledge of Actual K Seen by Electrons Effects Influencing Keff • Undulator Segment Tuning • Undulator Temperature • Transverse Segment Position • Segment Fiducialization and Alignment • Electron Beam Trajectory • Environmental Field in Undulator Hall • Radiation Damage See Tolerance Budget on next Slide Need for Beam Based Undulator K Measurements 9

  10. Segment Detuning Sub-Budget 10

  11. Discussions of Beam Based K Measurements Based on Spontaneous Undulator Radiation • January 2004 Z. Huang • Sven Reiche • September 2004: LCLS Diagnostics and Commissioning Workshop • High-Resolution Effective K Measurements Using Spontaneous Undulator Radiation, Bingxin Yang http://www-ssrl.slac.stanford.edu/lcls/workshops/2004-09-22_diag_comm/bxyang_CommWorkshop200409.ppt • October 2004: LCLS Week • Undulator / FEL Diagnostics, Bingxin Yang https://www-ssrl.slac.stanford.edu/lcls/fac/talks_oct2004/Yang_FAC200410.ppt • January 2005: LCLS FEL Physics Meeting • Simulation Results for 200-pC ("chargito") SASE performance with AC Wake, Jim Welch http://www-ssrl.slac.stanford.edu/lcls/internals/felphysics/2005-01-18/k_meas_talk.ppt • April 2005 ICFA Commissioning Workshop at Zeuthen (Work Package 6) • Measurement of Undulator Segment K_effective using Spontaneous Radiation in the Near Hall of the LCLS, Jim Welchhttp://adweb.desy.de/mpy/ICFA2005_Commissioning/Talks(PDF)/April%2021%20(Thursday)/WP6_1/Welch_Undulator%20Commissioning.pdf • High resolution undulator measurements using angle-integrated spontaneous spectra, Bingxin Yanghttp://adweb.desy.de/mpy/ICFA2005_Commissioning/Talks(PDF)/April%2021%20(Thursday)/WP6_2/Yang_High%20Resolution%20Undulator%20measurements.pdf • July 2005 LCLS Week: • K-Measurement Strategies discussion presented by Jim Welch and Bingxin Yang • October 2005 FAC Meeting • X-Ray Diagnostic, Richard Biontahttp://ssrl.slac.stanford.edu/lcls/fac/talks_oct_2005/bionta_xtod_diagnostics_fac.ppt 11

  12. Review of Existing LCLS Baseline Diagnostics Diagnostics presently being developed to Characterize Electron Beam and X-Ray Properties include • Electron Beam Diagnostics in the Linac-To-Undulator (LTU) Beamline • Electron Beam and X-Ray Diagnostics in the Undulator • Electron Beam Diagnostics after the Undulator (Dump Line) • X-Ray Diagnostics in the Front End Enclosure (FEE) 12

  13. LTU Electron Beam Diagnostics Control of Electron Beam Properties before Entrance into the Undulator 13

  14. LTU abort dump 1 OTR  slice-(e, b, g) OTR  slice E-spread (0.02%) 4 wires  e, b, g (+ collimators) 2 BPMs  energy jitter x1 x2 relative energy centroid resolution: 0.003% (5-mm BPMs) 14 Courtesy of Paul Emma

  15. X-Ray Beam Diagnostics Control of Electron Beam Trajectory inside the Undulator 15

  16. Short Break Section Components Beam Finder Wire RF Cavity BPM Undulator Segment Quadrupole Cherenkov Detector Undulator Segment 16 Courtesy of Dean Walters

  17. Long Break Section Components Beam Finder Wire Diagnostics Tank RF Cavity BPM Undulator Segment Quadrupole Cherenkov Detector Undulator Segment 17 Courtesy of Dean Walters

  18. After Undulator Electron Beam Diagnostics Electron Beam Diagnostics after Undulator 18

  19. Dump-Line 1 OTR  energy-spread (0.001%) 1 BPM  energy-jitter (0.003%) 19 Courtesy of Paul Emma

  20. Diagnostics in the Front End Enclosure Measurement of X-Ray Beam Properties in FEE 20

  21. FEE Layout Slit Diagnostics Package Be Mirrors 2 & 3 Solid Attenuator Collimator 1 Fast close valve Gas Attenuator Ion Chamber SiC Mirror 1 Ion Chamber Diagnostics Package SiC Mirror 2 21 Courtesy of Richard Bionta

  22. Desired Spontaneous Measurements 22 Courtesy of Richard Bionta

  23. FEE Cartoon Start of Experimental Hutches 5 mm diameter collimators Windowless Ion Chamber DiagnosticPackage Spectrometer / Indirect Imager mirror Solid Attenuator High-Energy Slit Total Energy Calorimeter e- WFOV Direct Imager Gas Attenuator FEL Offset mirror system Spectrometer camera Windowless Ion Chamber Muon Shield 23 Courtesy of Richard Bionta

  24. Redundant Commissioning Instrumentation 24 Courtesy of Richard Bionta

  25. LCLS FEL Commissioning Milestones MS3BO_040: Front End Beneficial Occupancy (9/5/2007) MS3BO_030: Undulator Facility Beneficial Occupancy (12/3/2007) MS3_XT040: Solid Attenuator Installation Complete (12/14/2007) MS3_XT045: Gas Attenuator Installation Complete (12/14/2007) MS3_XT080: Start Front End Enclosure Commissioning (3/4/2008) MS3_LN015: Start Linac-to-Undulator (LTU) Commissioning (5/12/2008) MS3_XT066: Start Near Experimental Hall Checkout (6/12/2008) MS3_UN020: Undulator System Installation Complete (7/18/2008) MS3_UN025: Start Undulator Commissioning (1st Light) (7/24/2008) Diagnostics needed around July 2008 25

  26. Workshop Objective • Define a strategy for using spontaneous undulator radiation to measure the K value of every individual LCLS Undulator Segment after installation in the Undulator Hall. • To reach the objective, the physics and technologies necessary need to be identified. Workshop discussions will include • Usable spectral features of spontaneous radiation • Strategies for beam-based K measurements • Specifications for suitable instruments • Scheduling issues • Three Work Packages have been defined and assigned to three different groups. Work described by these Work Packages has been carried out in preparation of the workshop and will be presented and discussed at the workshop. 26

  27. Workshop Agenda 27

  28. Work Package 1: Angle Integrated Measurement • Group: B. Yang, R. Dejus • Task: Examine robustness of angle-integrated measurements of undulator spectrum. Consider effects of errors in beam alignment, undulator magnet structure, straightness of vacuum pipe, alignment of spectrometer, etc. Consider effects of location of undulator segment being tested. Determine what are realistic values for the precision with which the value of K can be determined for an undulator segment at the beginning, middle, and end of the undulator. This task explores the use of the high-energy edge of the fundamental spectral peak (the third harmonic may also be considered) of a single undulator to measure its K parameter. The measuring spectrometer will be located in the LCLS FEE, roughly 100 m downstream from the final undulator segment. Realistic values for the angular acceptance of the measurement (limited by beam-pipe apertures, or apertures at the measuring point) should be considered. 28

  29. Work Package 2: Pinhole Measurement • Group: J. Welch, R. Bionta, S. Reiche • Task: Examine robustness of pinhole measurements of undulator spectrum. Consider effects of errors in beam alignment, undulator magnet structure, straightness of vacuum pipe, alignment of pinhole and spectrometer, etc. Consider effects of location of undulator segment being tested. Determine what are realistic values for the precision with which the value of K can be determined for an undulator segment at the beginning, middle, and end of the undulator. This task explores the use of the fundamental spectral peak (the third harmonic may also be considered) of a single undulator, as seen through a small angular aperture, to measure its K parameter. The measuring spectrometer will be located in the LCLS FEE, roughly 100 m downstream from the final undulator segment. Realistic values for the angular acceptance of the measurement should be determined, and the effects of misalignment of the aperture or undulator axis should be carefully considered. 29

  30. Work Package 3: Single-Shot Spectral Measurement • Group: J. Hastings, et al. • Task: Assume that a single shot spectral measurement is needed for an LCLS spontaneous undulator pulse. What are the best options for doing the measurement? What spectral resolution can be obtained using these methods? What are the effects of beam jitter, spectrometer misalignment, etc? This task explores the design and performance of x-ray spectrometers capable of providing centroid or edge position with high resolution, on a single-shot of radiation from a single LCLS undulator. The spectrometer will most likely be located in the LCLS FEE, about 100 m downstream from the final undulator segment. 30

  31. Workshop Charge Characterize the spectral features of spontaneous synchrotron radiation that are usable for beam-based K-measurements. Identify the most appropriate strategy for beam-based K-measurements. Specify suitable instruments for the identified beam-based K-measurement strategy. List expected performance parameters such as resolution of K measurement as function of beam charge, and segment location as well as expected tolerances to trajectory and energy jitter. List any open questions regarding the feasibility of the most appropriate strategy. List the R&D activities, if any, needed before the design of a measurement system can be completed and manufacturing/procurement can start. 31

  32. End of Presentation 32

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