1. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Undulator Specifications Heinz-Dieter Nuhn, SLAC / SSRL November 14, 2003 Undulator Overview FEL Performance Assessment Recent Undulator Parameter Changes Undulator Overview FEL Performance Assessment Recent Undulator Parameter Changes

2. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Linac Coherent Light Source Near Hall Far Hall Undulator

3. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL UNDULATOR 3,410406 11,905 mm Horizontal Steering Coil Vertical Steering Coil Beam Position Monitor 863 mm X-Ray Diagnostics Quadrupoles LCLS Undulator Schematic (Regular Section) 130,092 mmTotal Length

4. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL SASE FEL theory well developed and verified by simulations FEL radiation starts from noise in spontaneous radiation Transverse radiation electric field modulates the energy and bunches the electrons within an optical wavelength Exponential build-up of radiation along undulator length SASE FELs Undulator Regime Exponential Gain Regime Saturation 1 % of X-Ray Pulse Electron Bunch Micro-Bunching

5. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL 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 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 ParmelaParmelaElegantElegant Genesis / Ginger space-charge compression, wakes, CSR, … SASE FEL with wakes Start-To-End Simulations:

6. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Workshop on Start-To-End Simulations Beam Dynamics Mini Workshop Future Light Sources Start-To-End Simulations for SASE FELs (S2E 2003) Chaired by John Galayda (SLAC) and Joerg Rossbach (DESY) Dates August 18 – 22, 2003 Location DESY-Zeuthen, Berlin, Germany

7. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Comparison of GINGER/GENESIS results for 1-nC LCLS “0-order” Case Observations: GENESIS shows very slightly longer gain length, later saturation but higher power GINGER shows stronger post-saturation power oscillation (more deeply trapped particles?) Method for choosing best K was slightly different for both codes

8. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL GINGER/GENESIS results for “0-order” 200-pC case Observations: Again, GENESIS shows slightly longer gain length, 10-m later saturation but 15% higher power Again, GINGER shows deeper post- saturation power oscillation Little sensitivity (2 m, 7%) in GINGER results to 8X particle number increase Possible reasons for differences:   bugs   slight differences in initial e-beam properties (e.g. mismatch)   grid effects (e.g. outer boundary)   ???

9. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL 1-nC LCLS: “1st-order” envelope reconstruction: max P(z) vs. slice time 100 GW Some quick observations: Power suppressed in regions with high energy spread [-90:-70 fs] GENESIS shows ~2-3X greater power than GINGER for no-wake cases For runs including wake fields, GINGER shows somewhat more peak power for the main body (but more localized in time) Beam centroid wander may be important – better modeled by GENESIS GINGER GENESIS

10. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Tolerance Analysis: RON R. Dejus, N. Vinokurov Tolerance Analysis: RON R. Dejus, N. Vinokurov

11. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Undulator Performance Requirements (as of May 2003) Undulator Performance Requirements (as of May 2003) ParameterSymbolTarget(Nom.)UnitsTolerance (critical) Effective Undulator Parameter K3.711 ±0.015 % Average Gap Height g6.0mm+0.006 Average Period Length u30.00mm±0.03 Wiggle Plane horizontal— RMS Trajectory Straightness Tolerance xxxx2 mmmm— RMS Segment Phase Shake Tolerance 10degrees— 3.6350 6.5

12. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Trajectory Straightness Requirement Preserve transverse overlap between beam and radiation => Tolerance for betatron amplitude Tolerance for betatron amplitude < 8  m (beam radius dep.) Avoid longitudinal phase shake between beam and radiation => Tolerance for rms phase shake 10 degrees per module => Equivalent tolerance for rms electron beam straightness 2  m Preserve transverse overlap between beam and radiation => Tolerance for betatron amplitude Tolerance for betatron amplitude < 8  m (beam radius dep.) Avoid longitudinal phase shake between beam and radiation => Tolerance for rms phase shake 10 degrees per module => Equivalent tolerance for rms electron beam straightness 2  m

13. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Workshop on Undulator Parameters LCLS Undulator Parameter Workshop Chaired by Heinz-Dieter Nuhn (SLAC) Dates November 24, 2003 Location APS, Argonne, USA

14. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Workshop Focus Set Undulator Period Reduction of maximum available linac energy Undulator gap height increase Longer break distances Weaker FODO lattice Set Undulator Period Reduction of maximum available linac energy Undulator gap height increase Longer break distances Weaker FODO lattice

15. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Halbach formula for hybrid undulator is used to estimate relation between gap/period and on-axis field Measured prototype field 5.3% larger than estimated Halbach formula for hybrid undulator is used to estimate relation between gap/period and on-axis field Measured prototype field 5.3% larger than estimated Adjusting Estimate of On-Axis Undulator Field

16. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Undulator Period Present undulator period length of 3 cm is near optimum for shortest gain length Change of undulator period length would require more man-power and time than available before next review Undulator period length will be kept at u = 3.0 cm Present undulator period length of 3 cm is near optimum for shortest gain length Change of undulator period length would require more man-power and time than available before next review Undulator period length will be kept at u = 3.0 cm

17. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Maximum Available Linac Energy 14.35 GeV has been nominal energy to reach 1.5 Å Loss of available linac energy due to Reduction of available linac sections (incl. Injector relocation) Off-crest acceleration New maximum energy set to 14.1 GeV to restore operational overhead Requires change in K value 14.35 GeV has been nominal energy to reach 1.5 Å Loss of available linac energy due to Reduction of available linac sections (incl. Injector relocation) Off-crest acceleration New maximum energy set to 14.1 GeV to restore operational overhead Requires change in K value

18. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Undulator Gap Selection Undulator gap height changes still possible Present gap height: 6 mm Gap height corrected for measured field: 6.35 mm Parameter correction for reduced maximum energy Larger gap gives access to short wavelength 1.0 Å Undulator gap height changes still possible Present gap height: 6 mm Gap height corrected for measured field: 6.35 mm Parameter correction for reduced maximum energy Larger gap gives access to short wavelength 1.0 Å New Parameters RejectedRejected More Room for Vacuum Chamber

19. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Undulator Large Gap / Low K Proposal Proposed Undulator Length Emittance Goal Safety Overhead Emittance Achieved Based on Chosen Parameters

20. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL New Break Lengths Separations between undulator modules (breaks) designed to produce slippage by integer number of optical wavelength. Break increments for adding slippage of 1 optical wavelength is  L B = u (1+K 2 /2).  L B =23.7 cm (old); 22.8 cm (new) Present design uses break pattern 1-1-2 which corresponds to the lengths sequence 18.7 cm – 18.7 cm – 42.1 cm 18.7 cm gives not enough space for quads, BPMs, etc. Length needed > 30 cm 42.1 cm gives not enough space for x-ray diagnostics Length needed > 70 cm New break pattern 2-2-4 corresponding to length sequence 40.6 cm – 40.6 cm – 86.3 cm Separations between undulator modules (breaks) designed to produce slippage by integer number of optical wavelength. Break increments for adding slippage of 1 optical wavelength is  L B = u (1+K 2 /2).  L B =23.7 cm (old); 22.8 cm (new) Present design uses break pattern 1-1-2 which corresponds to the lengths sequence 18.7 cm – 18.7 cm – 42.1 cm 18.7 cm gives not enough space for quads, BPMs, etc. Length needed > 30 cm 42.1 cm gives not enough space for x-ray diagnostics Length needed > 70 cm New break pattern 2-2-4 corresponding to length sequence 40.6 cm – 40.6 cm – 86.3 cm

21. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Weaker FODO Lattice FODO Lattice had been designed for =18 m at 1.5 Å Required gradient of 106-107 T/m for 5 cm long quads New gradient set to 60 T/m to Increase Saturation Power Relax Beam-Based Alignment Tolerances Saturation length only slightly increased Average beta function at 1.5 Å is now =30 m Focusing and defocusing magnets will be identical FODO Lattice had been designed for =18 m at 1.5 Å Required gradient of 106-107 T/m for 5 cm long quads New gradient set to 60 T/m to Increase Saturation Power Relax Beam-Based Alignment Tolerances Saturation length only slightly increased Average beta function at 1.5 Å is now =30 m Focusing and defocusing magnets will be identical

22. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Optimum  -Function at Short Wavelength Optimum Beta-Function New Beta-Function 14.1 GeV

23. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (Old) LCLS Operating Point at 1.5 Å LCLS Operating Point at 15 Å

24. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (New) LCLS Operating Point at 1.5 Å Operating Point

25. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (New) LCLS Operating Point at 15 Å Operating Point

26. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Beam Based Alignment Tolerances (Paul Emma) 0.04 0 4444 100 100 2

27. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL OLDNEW Undulator Typeplanar hybrid planar hybrid Magnet MaterialNdFeB NdFeB Wiggle Planehorizontalhorizontal Gap66.5mm Period Length3.03.0cm Peak On-Axis Field1.3251.298T K3.7112.635 Module Length3.413.41m Number of Modules3333 Undulator Magnet Length112.5112.5m Break Length18.7-18.7-42.140.6-40.6-86.3cm Total Device Length121.8130.2m OLDNEW Undulator Typeplanar hybrid planar hybrid Magnet MaterialNdFeB NdFeB Wiggle Planehorizontalhorizontal Gap66.5mm Period Length3.03.0cm Peak On-Axis Field1.3251.298T K3.7112.635 Module Length3.413.41m Number of Modules3333 Undulator Magnet Length112.5112.5m Break Length18.7-18.7-42.140.6-40.6-86.3cm Total Device Length121.8130.2m Summary of Nominal Undulator Design Changes

28. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL OLDNEW Lattice TypeFODO FODO Magnet Typepermanent permanent Nominal Magnet Length55cm QF Gradient10760T/m QD Gradient-106-60T/m Average  Function at 1.5 Å18.030m Lowest Usable Energy3.171.84GeV OLDNEW Lattice TypeFODO FODO Magnet Typepermanent permanent Nominal Magnet Length55cm QF Gradient10760T/m QD Gradient-106-60T/m Average  Function at 1.5 Å18.030m Lowest Usable Energy3.171.84GeV Summary of Nominal Focusing Lattice Changes

29. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Summary of Electron Beam Parameters At 15 ÅOLDNEW Electron Beam Energy 4.45 4.46GeV  88808722 7.3 8.9m rms beam radius35 34  m At 15 ÅOLDNEW Electron Beam Energy 4.45 4.46GeV  88808722 7.3 8.9m rms beam radius35 34  m At 1.5 ÅOLDNEW Electron Beam Energy14.35 14.09GeV  28082 27580 18.030.0m rms beam radius3635  m At 1.5 ÅOLDNEW Electron Beam Energy14.35 14.09GeV  28082 27580 18.030.0m rms beam radius3635  m

30. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL ConclusionsConclusions Requirements for LCLS undulator are well established LCLS undulator performance requirements are well understood Risks have been assessed and undulator specifications address the risk New parameter values have been chosen Increase in undulator gap, reduction in maximum electron beam energy, longer break length, and reduced quadrupole gradients Benefits are more room for vacuum chamber more energy safety margin more space for diagnostics components between undulator modules increase of accessible wavelength range Requirements for LCLS undulator are well established LCLS undulator performance requirements are well understood Risks have been assessed and undulator specifications address the risk New parameter values have been chosen Increase in undulator gap, reduction in maximum electron beam energy, longer break length, and reduced quadrupole gradients Benefits are more room for vacuum chamber more energy safety margin more space for diagnostics components between undulator modules increase of accessible wavelength range

31. Undulator Specifications Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRL End of Presentation