1. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Physics Diagnostics / Commissioning Strategy Heinz-Dieter Nuhn, SLAC / SSRL April 29, 2004 Undulator Overview FEL Parameters Diagnostics and Commissioning Strategy Undulator Overview FEL Parameters Diagnostics and Commissioning Strategy

2. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Linac Coherent Light Source Near Hall Far Hall Undulator

3. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu

4. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Segment Prototype

5. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Type planar hybrid Magnet Material NdFeB Wiggle Planehorizontal Gap6.5mm Period Length3.0 ± 0.003cm Effective On-Axis Field1.296T Effective Undulator Parameter K3.630 ± 0.015 % Segment Phase Slippage Tolerance10degrees Module Length3.40m Number of Modules33 Undulator Magnet Length112.2m Standard Break Lengths49.6 - 49.6 - 72.3cm Total Device Length130.4m Lattice Type FODO Magnet Type permanent Nominal Magnet Length5cm QF Gradient60T/m QD Gradient-60T/m Average  Function at 1.5 Å (14.08 GeV)30m Average  Function at 15. Å (4.45 GeV)8.9m Lowest Usable Energy1.84GeV Undulator Type planar hybrid Magnet Material NdFeB Wiggle Planehorizontal Gap6.5mm Period Length3.0 ± 0.003cm Effective On-Axis Field1.296T Effective Undulator Parameter K3.630 ± 0.015 % Segment Phase Slippage Tolerance10degrees Module Length3.40m Number of Modules33 Undulator Magnet Length112.2m Standard Break Lengths49.6 - 49.6 - 72.3cm Total Device Length130.4m Lattice Type FODO Magnet Type permanent Nominal Magnet Length5cm QF Gradient60T/m QD Gradient-60T/m Average  Function at 1.5 Å (14.08 GeV)30m Average  Function at 15. Å (4.45 GeV)8.9m Lowest Usable Energy1.84GeV Summary of Nominal Undulator Parameters

6. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Beam Based Alignment Tolerances (Paul Emma)

7. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu FEL Simulations Parameter Range Wavelength Charge 15 Å1.5 Å 0.2 nC 1.0 nC strong wakefields losses due to spon. rad. deep saturation Operation Space Energy14.1 GeV4.4 GeV Current3.4 kA Charge0.2 - 1 nC Slice Emittance1.2 mm mrad Slice Energy Spread0.01 %0.025 % Undulator Period3 cm Undulator Parameter3.63  -function 18 m7.5 m Wavelength1.5 Å15 Å Lowering the charge reduces bunch length, current and emittance ParmelaParmelaElegantElegantGenesisGenesisspace-charge compression, wakes, CSR, … SASE FEL with wakes Start-To-End Simulations:

8. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Expected Performance Low charge cases are modeled in PARMELA after the GTF results and then imported into ELEGANT/GENESIS for the transport through the LCLS beam line. The simulations includes: Space charge in the gun Emittance compensation Wakefield and CSR effects Optimized beam transport (Jitter) Spontaneous Undulator Radiation All cases reach saturation

9. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Risk Assessment: Undulator Length Saturation predicted 40 m before undulator end Space for Undulator Extension Available if needed. Saturation predicted 40 m before undulator end Space for Undulator Extension Available if needed. Length of Undulator Hall175 m Length of Undulator130 m Length of Undulator Hall175 m Length of Undulator130 m Available Undulator Length Extendable Undulator Length Nominal Working Point 1.7 mm mrad 1.2 mm mrad

10. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Diagnostics and Commissioning Workshop LCLS Diagnostics and Commissioning Workshop Dates January 19-20, 2004 Location UCLA, Los Angeles, USA http://ssrl.slac.stanford.edu/lcls/undulator/meetings/2004-01-19_diagnostics_comissioning/ Workshop Website http://www-ssrl.slac.stanford.edu/lcls/technotes/lcls-tn-04-2.pdf http://www.slac.stanford.edu/pubs/slacreports/slac-r-715.html Workshop Report

11. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Goals End-Of-Construction Goal Defined by DOE to close-off construction project (CD-4) One of the first Commissioning Milestones Commissioning Goal Get LCLS ready for operation End-Of-Construction Goal Defined by DOE to close-off construction project (CD-4) One of the first Commissioning Milestones Commissioning Goal Get LCLS ready for operation

12. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu FEL Commissioning Scope Commissioning of the FEL Undulator with Beam Prerequisites Undulator, Diagnostics, Shielding, Beam Dump etc. in Place Commissioning Without Beam for all Components Complete Main Commissioning Tasks Characterization of Electron Beam Up-Stream of Undulator Establishment of a Good Beam Trajectory Through Undulator to Beam- Dump Characterization of Spontaneous Radiation Establishment of SASE Gain Characterization of FEL Radiation Scope Commissioning of the FEL Undulator with Beam Prerequisites Undulator, Diagnostics, Shielding, Beam Dump etc. in Place Commissioning Without Beam for all Components Complete Main Commissioning Tasks Characterization of Electron Beam Up-Stream of Undulator Establishment of a Good Beam Trajectory Through Undulator to Beam- Dump Characterization of Spontaneous Radiation Establishment of SASE Gain Characterization of FEL Radiation Low Charge, Single Shot Low Charge, 10 Hz 10 Hz

13. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Issues Undulator Radiation Protection Measurements of FEL Radiation vs. Z Radiation Power Damage to Inter Undulator X-Ray Diagnostics End-of-Undulator Diagnostics Beam Based Detection of Gain Reducing Errors Using Spontaneous Radiation Using FEL Gain Curve Numerical Simulation Support for Detector Development and Commissioning Undulator Radiation Protection Measurements of FEL Radiation vs. Z Radiation Power Damage to Inter Undulator X-Ray Diagnostics End-of-Undulator Diagnostics Beam Based Detection of Gain Reducing Errors Using Spontaneous Radiation Using FEL Gain Curve Numerical Simulation Support for Detector Development and Commissioning

14. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu  /2  /2 x1x1x1x1 x2x2x2x2 x3x3x3x3 phase-1 phase-2 phase-1 again halo e  beam mm  3 mm 2 mm  2 mm Two-Phase, Two-Plane Collimation, 1½ Times undulator beam pipe 5 mm  2.5 mm edge scattering (also collimation in y and energy – see next slides) Courtesy of P. Emma Undulator Undulator Radiation Protection

15. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu E1E1E1E1 E2E2E2E2 x1x1x1x1 y1y1y1y1 x2x2x2x2 y2y2y2y2 x3x3x3x3 y3y3y3y3 LCLS Collimation Proposal (2 energy, 3 x, and 3 y adjustable collimators) muon shieldin g undulato r x 3 & y 3 optional? Courtesy of P. Emma

16. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu 2 nd -order tracking with all collimators closed and big halo  2.5 mm 2-phase, 2-plane, and energy collimation in 2 nd -order well shadowed in x, y, and E ?- CY 3 -? CX 3  2.0- CY 2 -  2.0 CX 2  2.0- CY 1 -  2.0 CX 1 -  5.0 CE 2 -  5.0 CE 1  y mm  x mm Coll.  x,y = 4000  m,  E /E = 10% (uniform) Courtesy of P. Emma

17. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Trajectory through undulator at 14 GeV after 3 passes of BBA procedure. Trajectory After BBA Convergence 2-  m BPM resolution 50-  m initial BPM & quad offsets  1-  m mover backlash 14-7-4.5 GeV   204° 2-  m BPM resolution 50-  m initial BPM & quad offsets  1-  m mover backlash 14-7-4.5 GeV   204° + Quadrupole positions positions o BPM readback e  trajectory e  trajectory Courtesy of P. Emma

18. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu BPM read-backs through undulator at 14 GeV (top) and 4.5 GeV (bottom) after rough steering, but before the BBA procedure. The energy is changed and the launch is re- established. Trajectory changes are expected at the 500-  m level. 500  m Verify BBA Convergence by noting orbit change from 14 to 4.5 GeV Before BBA procedure 14.1 GeV 4.5 GeV drop energy, reset launch, note change Courtesy of P. Emma

19. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu BPM read-backs through undulator (note scale change) at 14 GeV (top) and 4.5 GeV (bottom) after three rounds of the BBA procedure, where trajectory changes with energy are expected at the 20-  m level. 20  m Verifying BBA Convergence After BBA procedure drop energy, reset launch, note change 14.1 GeV 4.5 GeV Courtesy of P. Emma

20. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu G = 110 T/m Track 100 times with: DL2 BPM rms res. = 10  m DL2 BPM rms misa. = 200  m DL2 Quad rms misa. = 200  m Undulator Quad rms misa. = 100  m Correct und-launch, then open stopper-2 for one beam shot… Just 11 of 100 trajectories exceed  2.5 mm within undulator None exceed  3.5 mm First beam shot through undulator? Courtesy of P. Emma

21. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Desirable measurements as function of position along undulator : Intensity (LG, Saturation) Spectral Distribution Bunching Desirable measurements as function of position along undulator : Intensity (LG, Saturation) Spectral Distribution Bunching FEL Gain Measurement Undulator Regime Exponential Gain Regime Saturation 1 % of X-Ray Pulse Electron Bunch Micro-Bunching

22. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Dose / Power Considerations Fluence to Melt Energy Density Reduction of a Reflector Be will melt at normal incidence at E < 3 KeV near undulator exit. Using Be as a grazing incidence reflector may gain x 10 in tolerance. Courtesy of R. Bionta

23. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu End-of-Undulator Commissioning Diagnostics Measurements Total energy Pulse length Photon energy spectra Spatial coherence Spatial shape and centroid Divergence Measurements Total energy Pulse length Photon energy spectra Spatial coherence Spatial shape and centroid Divergence

24. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Fast close valve Slit A PPS 13' Muon shield Gas Attenuator Solid Attenuator Slit B PPS 4' Muon shield Windowless Ion Chamber Direct Imager Indirect Imager Spectrometer, Total Energy PPS Access Shaft Access Shaft Courtesy of R. Bionta

25. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Measurement of SASE Gain along the undulator Direct: Detectors in the Breaks between Undulator Segments. No good solution for x-ray detector in existence, yet. Alternative: Characterize x-ray beam at single station down stream of undulator after gain is turned off at a selectable point along undulator by introduction of orbit distortion. (Initial studies by Z. Huang) removal of undulator segments (Changed Design) opening of gap if undulator is variable gap device. (Changed Design) Direct: Detectors in the Breaks between Undulator Segments. No good solution for x-ray detector in existence, yet. Alternative: Characterize x-ray beam at single station down stream of undulator after gain is turned off at a selectable point along undulator by introduction of orbit distortion. (Initial studies by Z. Huang) removal of undulator segments (Changed Design) opening of gap if undulator is variable gap device. (Changed Design)

26. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Measurement of SASE Gain with end-of-undulator diagnostics GENESIS Simulations by Z. Huang

27. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Spontaneous vs. FEL Radiation-1- Figure by S. Reiche

28. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Spontaneous vs. FEL Radiation -2- Figure by S. Reiche

29. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Startup at 15 Å with highly degraded e  beam quality FEL gain highly likely in initial commissioning stages – can check out undulator, characterize e  beam, and boot-strap up to shorter wavelengths.

30. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Spontaneous vs. FEL Radiation -3- Figure by S. Reiche

31. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Workshop Recommendations No Intra-Undulator-Segment X-Ray Diagnostics in Baseline Design Instead: End-of-Undulator X-Ray Diagnostics CCD Camera (9 mm Pixel Resolution, 1024 x 1024 Area) Spectrometer Trajectory Distortion Method to Characterize FEL Radiation vs. z Investigation of Spontaneous Radiation as Diagnostics Tools Code Development to Support Commissioning Areas for Follow-Up R&D Study of Spectral and Spatial Distribution of Spontaneous Radiation Diagnostics Prototyping Microbunching Measurement No Intra-Undulator-Segment X-Ray Diagnostics in Baseline Design Instead: End-of-Undulator X-Ray Diagnostics CCD Camera (9 mm Pixel Resolution, 1024 x 1024 Area) Spectrometer Trajectory Distortion Method to Characterize FEL Radiation vs. z Investigation of Spontaneous Radiation as Diagnostics Tools Code Development to Support Commissioning Areas for Follow-Up R&D Study of Spectral and Spatial Distribution of Spontaneous Radiation Diagnostics Prototyping Microbunching Measurement

32. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Draft Commissioning Schedule

33. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Conclusions Requirements for LCLS undulator are well established LCLS undulator performance requirements are well understood Risks have been assessed and undulator specifications address the risk Commissioning plan is under development Requirements for LCLS undulator are well established LCLS undulator performance requirements are well understood Risks have been assessed and undulator specifications address the risk Commissioning plan is under development

34. Undulator Physics April 29, 2004 Heinz-Dieter Nuhn, SLAC / SSRL Facility Advisory Committee Meeting Nuhn@slac.stanford.edu End of Presentation