1. Undulator Physics Diagnostics / Commissioning Strategy Heinz-Dieter Nuhn, SLAC / SSRL August 11, 2004
Undulator Overview
FEL Parameters
Diagnostics and Commissioning Strategy

2. Linac Coherent Light Source
Undulator
Near Hall
Far Hall

4. Undulator Segment Prototype

5. Workshops and Meetings
Undulator Parameter Workshop
October 24, 2003, Argonne
URL:
Undulator Review
November 14, 2003, Argonne
URL:
Undulator Diagnostics and Commissioning Workshop
January 19-20, 2004, UCLA
URL:
Report:
Undulator Systems Review
March 3-4, 2004, Argonne
URL:
Undulator Physics and Engineering Meeting
June 28-29, 2004, Argonne
URL:
Undulator Meeting
July 23, 2004, Argonne
URL:
LCLS Diagnostics and Commissioning Workshop
September 22-23, 2004, SLAC
URL:

6. Undulator Design Changes Since May 2003
Canting of Undulator Poles
Remote Undulator Roll-Away and K Adjustment Function
Increase in Undulator Gap
Reduction in Maximum Beam Energy
Reduction in Quadrupole Gradient
Increase in Beta Function
Increase in Break Section Length

7. Amplitudes of Undulator Parameter Changes
May 2003 August 2004
Undulator Type planar hybrid
Magnet Material NdFeB
Wiggle Plane horizontal
Gap mm
Gap Canting Angle mrad
Period Length ± 0.1 mm
Effective On-Axis Field T
Effective Undulator Parameter K ± 0.015% ± 0.015%
Module Length m
Number of Modules 33
Undulator Magnet Length m
Standard Break Lengths cm
Total Device Length m
Lattice Type FODO
Integrated QF Gradient T/m
Integrated QD Gradient T/m
Average b Function at 1.5 Å m
Average b Function at 15. Å m

8. Performance Impact of Changes (1.5 Å)
May 2003 August Change
Electron Beam Energy GeV -5.0 %
Emittance nm rad +5.2 %
Avg. Electron Beam Radius µm %
Avg. Electron Beam Divergence µrad %
Peak Beam Power TW -5.0 %
FEL Parameter (3D) %
Power Gain Length (3D) m +3.6 %
Saturation Length (w/o Breaks) m +4.9 %
Saturation Length (w/ Breaks) m %
Peak Saturation Power GW +2.5 %*
Coherent Photons per Pulse 1.4× × %*
Peak Brightness 1.5× ×1033 ** +2.5 %*
Average Brightness 4.6× ×1022 ** +2.5 %*
Peak Spont. Power per Pulse GW %
*Increase due to 3D effects (reduction in diffraction due to beam radius increase)
** [Ph./s/mm2/mr2/.1%]

9. Undulator Specification Documents
Controlled Specification Documents support Inter-Laboratory Communications
Global Requirements Document (GRD)
GRD (
Physics Requirements Documents (PRDs)
PRD General Undulator System Requirements (
PRD Magnetic Measurement Facility Requirements (
PRD Beam Based Alignments System Requirements (
PRD LCLS Beam Position Measurement System Requirements (
Engineering Specification Documents (ESDs)
ESD Undulator Segment Specifications
ESD Undulator Segment Support Specifications
ESD Quadrupole Magnet Specifications
ESD Diagnostics System Specifications
ESD Wire Position Monitor System Specifications
ESD Hydrostatic Leveling System Specification
ESD Vacuum System Specifications
ESD Controls Specifications
Interface Control Documents (ICDs)
ICD Undulator Mechanical Interfaces
Process of generating these documents is on-going.

10. FEL Commissioning Workshop 1/19-20/04
Scope
Commissioning of the FEL Undulator with Beam
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
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

11. Workshop 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

12. Undulator Radiation Protection
Two-Phase, Two-Plane Collimation, 1½ Times
p/2
~p/2
3 mm
edge scattering
2.5 mm
2 mm
halo
e- beam
undulator beam pipe x1 x2 x3
phase-1 again
phase-1
phase-2
(also collimation in y and energy – see next slides)

13. E1 E2 x1 y1 x2 y2 x3 y3
LCLS Collimation Proposal (2 energy, 3 x, and 3 y adjustable collimators)
muon shielding
undulator
x3 & y optional?

14. well shadowed in x, y, and E
2nd-order tracking with all collimators closed and big halo
2.5 mm
2-phase, 2-plane, and energy collimation in 2nd-order
well shadowed in x, y, and E ? -
CY3
CX3
2.0
CY2
CX2
CY1
CX1
5.0
CE2
CE1 Dy mm Dx
Coll.
gex,y = 4000 mm,
sE/E = 10% (uniform)

15. First beam shot through undulator?
Track 100 times with:
DL2 BPM rms res. = 10 mm
DL2 BPM rms misa. = 200 mm
DL2 Quad rms misa. = 200 mm
Undulator Quad rms misa. = 100 mm
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
G = 110 T/m
First beam shot through undulator?

16. FEL Gain Measurement
Desirable measurements as function of position along undulator :
Intensity (LG, Saturation)
Spectral Distribution
Bunching
Saturation
Exponential Gain Regime
Undulator Regime
1 % of X-Ray Pulse
Electron Bunch Micro-Bunching

17. 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.

18. End-of-Undulator Commissioning Diagnostics
Measurements
Total energy
Pulse length
Photon energy spectra
Spatial coherence
Spatial shape and centroid
Divergence

19. 4'
Muon
shield
PPS
Access
Shaft
PPS
Spectrometer,
Total Energy
Solid
Attenuator
Access
Shaft
Direct Imager
Indirect Imager
Slit A
Slit B
Windowless
Ion
Chamber
PPS
Gas Attenuator
13'
Muon
shield
Fast
close
valve

20. 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: End-Of-Undulator Diagnostics
Turn-Off Gain at Selectable Point Along Undulator by
Introduction of orbit distortion
Removal of undulator segments (New roll-away option)
Characterize x-ray beam at single station down stream of undulator

21. Measurement of SASE Gain with end-of-undulator diagnostics
GENESIS Simulations by Z. Huang

22. Spontaneous vs. FEL Radiation -1-

23. Spontaneous vs. FEL Radiation -2-

24. Workshop Recommendations
No Intra-Undulator-Segment X-Ray Diagnostics in Baseline Design
Instead: End-of-Undulator X-Ray Diagnostics to Characterize FEL Radiation vs. z
Trajectory Distortion Method
Roll-Away Undulator Segments Function
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

25. Requirements for LCLS undulator are well established
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
Detailed commissioning strategy is being developed. Startup Test Plan exists.
PRD LCLS Start-Up Test Plan (

26. End of Presentation