1. Physics Performance Details Heinz-Dieter Nuhn, SLAC / SSRL March 3, 2004
Undulator Overview
FEL Performance Assessment
Recent Undulator Parameter Changes
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

2. Linac Coherent Light Source
Undulator
Near Hall
Far Hall
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

3. LCLS Undulator Schematic (Regular Section)
3,400
496
723 mm
UNDULATOR
11,915 mm
Weak Horizontal Steering Coil
Total Lattice Length
131,120 mm
Weak Vertical Steering Coil
Total Device Length
130,397 mm
Beam Position Monitor
Wire/OTR Region
Quadrupoles
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

4. Undulator Performance Requirements
Parameter
Symbol
Target
(Nom.)
Units
Tolerance
(critical)
Effective Undulator Parameter K
3.630
±0.015 %
Average Gap Height g
6.5 mm
Average Period Length lu
30.00
±0.03
Wiggle Plane
horizontal —
Trajectory Straightness Tolerance Dx 2
Segment Phase Slippage Tolerance Df 10
degrees
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

5. Tolerance Analysis: RON
R. Dejus, N. Vinokurov
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

6. Trajectory Straightness Requirement
Preserve transverse overlap between beam and radiation
=> Tolerance for betatron amplitude < 8 mm (beam radius dep.)
Avoid longitudinal phase slippage between beam and radiation
=> Tolerance for rms phase shake 10 degrees per module
=> Equivalent tolerance for rms electron beam straightness 2 mm
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

7. Beam Based Alignment Tolerances (Paul Emma)2
100
100
0.04 4
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

8. Summary of Nominal Undulator Parameters
Undulator Type planar hybrid
Magnet Material NdFeB
Wiggle Plane horizontal
Gap 6.5 mm
Period Length 3.0 cm
Effective On-Axis Field T K
Module Length 3.40 m
Number of Modules 33
Undulator Magnet Length m
Break Length cm
Total Device Length m
Lattice Type FODO
Magnet Type permanent
Nominal Magnet Length 5 cm
QF Gradient 60 T/m
QD Gradient -60 T/m
Average b Function at 1.5 Å (14.09 GeV) 30 m
Average b Function at 15. Å (4.46 GeV) 8.9 m
Lowest Usable Energy 1.84 GeV
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

9. LCLS Operating Points for 1 nC Bunch Charge (New)
LCLS Operating Point at 1.5 Å
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

10. LCLS Operating Points for 1 nC Bunch Charge (New)
LCLS Operating Point at 15 Å
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

11. Vacuum Chamber Wakefields
b=2.5 mm copper surface ls=20 microns, hrms=100 nm
g_eff=12.3 mm, l_module=3.5 m
Predicted LCLS Current Profile
mean
rms
Energy Change
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

12. Relative Wakefield Contributions
keV/m
mean
rms
b=2.5 mm RS
100.0%
copper surface GS
5.0%
8.4%
ls=50 microns, hrms=100 nm SM
0.0000
0.0% GO
6.2529
10.7%
2.8%
g_eff=12.3 mm, Lmodule=3.5 m
Total
115.7%
102.2%
77.733
19.5%
35.0%
ls=20 microns, hrms=100 nm
0.5117
0.1%
0.2%
130.3%
112.8%
Resistive
Surface Roughness
Geometric
Resistive
Surface Roughness
Geometric
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

13. Longitudinal Aspect Ratios for Surface Roughness Wakefields
Relative Contribution of Roughness Wakefield is small for Aspect Ratios > 200
Threshold for Noticeable Contribution is Describable by Aspect Ratio
Constant rms
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

14. Workshop on Undulator Parameters
LCLS Undulator Parameter Workshop
Chaired by
Heinz-Dieter Nuhn (SLAC)
Workshop Recommendations
Set Undulator Period
Reduction of maximum available linac energy
Undulator gap height increase
Longer break distances
Weaker FODO lattice
Dates
October 24, 2003
Location
APS, Argonne, USA
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

15. Undulator Review LCLS Undulator Review
Chaired by
Review Recommendations related to K adjustments
Canted Undulator Poles instead of Comb Device
Kem Robinson (LBNL)
Dates
November 13, 2003
Location
APS, Argonne, USA
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

16. Diagnostics and Commissioning Workshop
LCLS Diagnostics and Commissioning Workshop
Workshop Recommendations
No X-Ray Diagnostics in break sections
Use X-Ray Diagnostics Down Stream of Undulator
Use trajectory distortion method to characterize FEL radiation vs. z.
Investigate Use of Spontaneous Radiation to Characterize Undulator Performance
Commissioning Steps
Spontaneous Radiation Characterization
15 Angstrom FEL Characterization
Shorter Wavelength FEL Characterization
Chaired by
Heinz-Dieter Nuhn (SLAC)
Dates
January 19-20, 2004
Location
UCLA, Los Angeles, USA
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

17. Measurement of SASE Gain along the undulator
GENESIS Simulations by Z. Huang
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

18. Spontaneous vs. FEL Radiation -1-
Figure by S. Reiche
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

19. Spontaneous vs. FEL Radiation -2-
Figure by S. Reiche
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

20. Spontaneous vs. FEL Radiation -3-
Figure by S. Reiche
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

21. Baseline Parameter Choices
Minimal Performance Configuration
Canted poles with fixed offset for setting K in the MMF only
BPMs and quads fixed to the undulator strongback
No remote K adjustment
No roll away undulators
5 degrees of freedom remote motion control for the Quadrupole-Undulator-BPM unit
Horizontal gap
Permanent magnet quadrupoles
Hydrostatic Leveling System (HLS), Wire position monitor (WPS)
Possible enhancement (design revisions)
Remotely controlled K adjustment, preferably without requiring undulator motion.
Roll-away capability
Electromagnetic quads or coils on permanent magnet quads to measure the beam position relative to the quadrupole center
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

22. 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
Small parameter adjustments are being made as the undulator design goes into greater detail and commissioning procedures are being worked out.
Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL

23. End of Presentation Undulator Systems Review, March 3 - 4, 2004
Heinz-Dieter Nuhn, SLAC / SSRL