1. Magnetic Measurements For The LCLS Undulator System
Zack Wolf, Yurii Levashov,
Achim Weidemann, Seva Kaplounenko,
Scott Jansson, Ralph Colon, Dave Jensen

2. Introduction The LCLS will consist of 33 undulator segments.
The last 1/3 of the linac is used to produce the electron beam.
Some Parameters:
Ebeam = Gev
λr = 1.5 Å
Planar permanent magnet undulators
Nd Fe B permanent magnets
λu = 30 mm
Gap = 6.8 mm
Tapered gap, 4.5 mrad
Bfirst = T, tapered, nominal field, first undulator
Kfirst = 3.5, tapered, each undulator has its own K
226 poles per segment
Each segment is 3.4 m long

3. LCLS Location
J. Galayda

4. Schedule A S O N D J F M A M J J A S O N D J F M A M J J 2006 2007
Drive-Laser Commissioning
LTU/und. Install
Drive-Laser Installed
Controls
Checkout
LTU/und.
hall “ready”
First Spont. Light A S O N D J F M A M J J A S O N D J F M A M J J
2006
2007
2008
Gun/Inj./BC1 Install
(8/21 – 2/20)
Gun/Inj./BC1 Commissioning
Inj./Linac/BC2 Commissioning
linac/BC2 Install
LTU/und. Commissioning
Dave Schultz

5. Magnetic Measurement Facility
Undulator Tuning
Magnetic Measurement Facility

6. Magnetic Measurement Facility
Floor plan divided into three functional areas
Magnetic Measurements (± 0.1º C)
Fiducialization and Assembly (± 1º C)
Storage (± 2.5º C)
Test stand lay-out is driven by requirement to match the Earth Magnetic Field conditions in lab to Undulator Hall, i.e. azimuth and gap orientation need to be identical
LCLS-TN-04-1

7. Undulator Movements In MMF
Tuning Time:
about 4 weeks
1 Week, Fine Tuning
1 Week, Rough Tuning
1 Week, Come to 20 C
<1 Week, Finish
Fiducialization
Peak Throughput:
1 undulator per week

8. MMF Temperature Achim Weidemann Time history at the
Kugler bench
In general, the system meets stability requirements

9. Rough Tuning Bench Components

10. Rough Tuning Bench Reference Pole Undulator Cam Movers
Zero Gauss Chamber
Cable Handling
Bench

11. Capacitive Sensor Alignment Performance
Undulator mechanically aligned to bench in 15 minutes
Yurii Levashov

12. Scans Begin And End In A Zero Gauss Chamber
Beginning
zero field
measurement
Ending
zero field
measurement
Senis Hall probe
Zero Offset Correction
Assume linear offset dependence on time

13. Gap Shims
Tapered Shim
ANL TB-48

14. Isaac Vasserman’s Ideas
X Trajectory Shims
Isaac Vasserman’s Ideas
ANL/APS/TB-48
ANL/APS/TB-48
Apply shims to top and bottom poles
Shims weaken By, don’t cause Bx
Can’t strengthen pole, instead place shims on next pole to reduce deflection in other direction
Developed software to automate shim placement
LCLS-TN-04-7

15. Y Trajectory Shims Yurii Levashov Bx Shim New Design
Smaller external fields
Uniform Bx field in gap
Old
Shim
Design
Inconel
Steel
Spot weld
Yurii Levashov

16. Straighten X And Y Trajectories
Measured X
Trajectory
Calculate
Shims
Modeled
X Traj
With
Calc
Shims
Measured
X Traj
After Calc
Shims
Applied
The Shimming Is Automated

17. Phase Shims Measure By with a Hall probe Calculate phase error
LCLS-TN-04-7
ANL/APS/TB-48
Measure By with a Hall probe
Calculate phase error
Calculate shims to correct error
Apply shims, repeat
Developed software to automate
shim placement
We don’t have shims to strengthen
a magnet, only weaken
Must locally reduce the gap to
increase phase shift

18. Rough Tuning Test Plan Achim Weidemann 1) Place undulator
Use kinematic mount
2) Mechanically align to test stand
Optical alignment check, use capacitive sensors and cam movers
3) Magnetically align Hall probe to undulator
Move Hall probe in x and y to magnetic center
4) Rough tuning
Tune x and y trajectories, anticipate magnetic shield
5) Adjust gap
Measure K, adjust gap to set K to required value for that undulator
6) Check alignment
Alignment may have changed from gap adjustment
7) Rough tuning
Anticipate magnetic shield
8) Add magnetic shield
9) Check tuning

19. Each Undulator Has Its Own K Value
From Heinz-Dieter Nuhn

20. Fine Tuning Bench Components

21. Fine Tuning Bench Undulator With Magnetic Shield Cable Handling
Cam Movers
Kugler Bench
Steel Girder
And Stands

22. Kugler Bench Performance
Measurements by Georg Gassner
X Y straightness spec: < 14 μm
Pitch and yaw spec: < 4.2 μrad
Specs met in long block region

23. Coils For Fine Tuning Bench
Bx, By One Undulator Period Long Coils
Short Coil Zero Gauss Chamber I1 I2
Field Integral Coil
Dave Jensen

24. Fine Tuning Test Plan Yurii Levashov 1) Place undulator
Use kinematic mount, use steel girder and stands, shield on
2) Mechanically align to test stand
Optical alignment check, use capacitive sensors and cam movers
3) Magnetically align Hall probe to undulator
Move Hall probe in x and y to magnetic center
4) Determine the tuning axis
Move in x to where K has the required value
5) Tuning
Tune x and y trajectories, phase
6) Add phase matching shims
7) Adjust field integrals
Use long coil, I1 and I2 for both Bx and By
8) Adjust field uniformity
Add quadrupole and sextupole shims as necessary
9) Final checks before gluing shims
Check x and y trajectory, phase, phase matching, field integrals, uniformity

25. Fine Tuning Test Plan (cont.)
10) Glue shims in place
Remove y trajectory, quadrupole, sextupole, and phase shims,
apply glue, replace
11) Check the gap
Make sure no parts of a shim protrude into the gap
12) Check for errors while gluing shims
Check x and y trajectories, phase, I1 and I2 of Bx and By, uniformity
13) Map Bx and By in the retracted position
14) Final results data set
Measure Bx and By at x = -6, -5, …, 6 mm, y = -0.2, -0.08, , 0.2 mm,
calculate field integrals vs z, 65 scans
15) Find the x position, y=0, where K has the required value
16) Add fiducialization magnets to both ends
Measure offsets from beam axis to the center of the fiducialization magnets
17) Rough fiducialization using alignment equipment
18) Measure roll on flats at each undulator end
19) Move undulator to CMM, finish fiducialization

26. Fiducialization, Determine K vs X
Set the probe position to give the nominal K value.

27. Fiducialization

28. Hall Probe Calibration
Water NMR
HP3458
Chiller
For probe
temperature
Magnet
Metrolab
NMR
Seva Kaplounenko

29. Schedule
Robert Ruland

30. Quadrupole Fiducialization System
LCLS-TN-05-11

31. Quadrupole Fiducialization Vibrating Wire Technique
Move wire until the vibration stops:
Quadrupole Center
Force On Wire
A. Temnykh, NIM A 399 (1997) 185.

32. Detector Signal vs Quad Position

33. Pitch and Yaw Measurements

34. Quadrupole Fiducialization
Schematic
System Overview
Wire Vibration Sensor
Wire Finder

35. Conclusion
MMF construction is complete, temperature stability and set point accuracy
requirements have been met
The rough tuning bench is complete
The Hall probe calibration system is complete
The fine tuning bench has all components complete. A stage is being
repaired for the long coil system. Afterward, the bench will be complete.
The software is complete. Some automation work and improvements
are still being done.
Mechanical alignment takes about 15 minutes.
The fine tuning bench construction meets all specifications.
The expected throughput is one undulator per week. Each undulator,
however, spends about 4 weeks in the MMF.
One reference undulator gets re-measured every fourth undulator.
We have begun production undulator tuning.