1. LCLS Undulator Magnetic Measurements
Zack Wolf,
Scott Anderson, Ralph Colon, Brendan Dix, Scott Jansson, Dave Jensen, Luis Juarez,
Seva Kaplounenko, Yurii Levashov,
Wei Wang, Achim Weidemann

2. Undulator Tuning, General Approach
Use ANL and DESY experience
Techniques have been developed at ANL and DESY which work very well.
We will use the best of the ANL and DESY measurement techniques as our starting point (both have been very generous in sharing with us).
We need to adapt for production measurements.

3. SLAC 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

4. MMF Under Construction
Photos courtesy of Javier Sevilla
Beneficial occupancy in March

5. Important Dates MMF Major Construction Finished Feb. 17, 2006
(Approximate)
MMF Major Construction Finished Feb. 17, 2006
MMF Beneficial Occupancy March 6, 2006
Kugler Bench Complete April 15, 2006
Kugler Bench At SLAC May 15, 2006
Kugler Bench Handover To SLAC June 15, 2006
1st Article Arrives At SLAC July 2, 2006
MMF Ready For Measurements July 28, 2006
Production Measurements Start August 29, 2006

6. Kugler Bench
On order, expected at SLAC May 15, Ready for use June 15, 2006.

7. SLAC Software Development Bench
(While we wait
on the Kugler
bench)
Bench software by Seva Kaplounenko

8. Undulator Measurement Steps ANL Bench (1 Week)
Place undulator
Mechanically align undulator to bench
Magnetically align Hall probe to undulator
Determine and use shield effect correction
Rough tuning, x & y trajectories, phase
Measure K
Perform any required large gap adjustments
Re-align, repeat rough tuning
Attach magnetic shield
Repeat rough tuning
LCLS-TN-03-7

9. Undulator Measurement Steps Kugler Bench (1 Week)
Place undulator
Mechanically align undulator to bench
Magnetically align Hall probe to undulator
Rough tuning, x & y trajectories, phase
Add phase matching shims
Adjust field integrals
Measure and tune field quality
Final tuning, x & y trajectories, phase, check I1 & I2
Glue shims in place, check tuning
Measure Bx & By in retracted position
Map K vs X, move probe to the X value which gives the specified K
Add fiducialization magnets to undulator ends, locate center of fiducialization magnets
Rough fiducialization, Faro arm
Move undulator to CMM, finish fiducialization

10. Place Undulator
Ben Poling placing the ANL prototype on the SLAC prototype bench 12/9/05.

11. Built by Gordon Bowden, Yurii Levashov, Scott Jansson
Place Undulator
SLAC CAM Movers
Bearing
Bearing
Cam
Potentiometer
Harmonic
Drive
Motor
Brake
Built by Gordon Bowden, Yurii Levashov, Scott Jansson

12. Mechanically Align to Bench
Use Capacitive Sensors
Yurii Levashov
We tested capacitive sensors in TTF undulators at DESY

13. Mechanically Align To Bench
Undulator aligned to fixed height of reference pole.

14. Mechanically Align to Bench
Previous experience from PEP II and SPEAR III
Use 6 capacitive sensors on an arm
Gives x, yaw, y, pitch, and roll
Have reference poles at each end
Calibrate sensors with micrometers

15. Magnetically Align Hall ProbeBy x By By y x
Technique
Every N’th pole, move probe vertically,
find minimum
Every N’th pole, move probe horizontally,
find midpoint between edges
Plot (x, y) vs z, fit for magnetic alignment

16. Magnetically Align Hall Probe
SLAC Measurements

17. Perform Any Large Gap Adjustments
Tapered Shim
ANL TB-48

18. Straighten X And Y Trajectories
Simultaneously measure
Bx and By (Hall)
and Bx from a coil
LCLS-TN-05-5

19. Straighten X And Y Trajectories
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
Developing software to try to automate shim placement
LCLS-TN-04-7

20. Straighten X And Y Trajectories
Measured X
Trajectory
Calculate
Shims
Modeled
X Traj
With
Calc
Shims
Measured
X Traj
After Calc
Shims
Applied
Automate Shimming, Under Development

21. Check Hall Probe Field Integrals
LCLS-TN-05-22
Long Coil
150 Turns I1 I2

22. Earth’s Field LCLS-TN-05-4 We will Tune with the tunnel orientation
Add a girder to the Kugler bench undulator supports (Joachim)
Put a mu-metal shield around the undulators (Isaac)
d) Measure the fields in the tunnel, test in the MMF

23. Poles 51 and 52 are 1% too strong.
Minimize Phase Errors
A magnet which is too strong can cause phase errors.
The trajectory is shifted, but there is no residual slope.
Correct with phase shims.
Poles 51 and 52 are 1% too strong.
LCLS-TN-04-7
Measured
Phase
Errors
Calculated
Shims
Under development

24. Minimize Phase Errors Measure By with a Hall probe
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
Developing 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

25. Phase Matching pi/2 pi pi/2 (mod 2pi)
Program provides shim information
Phase Matching Shim Data
Entrance:
Number of end poles = 5
Measured Phase At The Entrance Poles:
(Phase = 0 at the entrance cell boundary.)
Pole Number =
Phase (deg) =
Expected phase at pole number 6 = deg
Entrance phase error (from pole 6) = deg
Entrance phase match shim dimension = e+000 m
(under development)

26. Determine K vs X Sinusoidal Field Canted Poles
LCLS-TN-04-7
Analysis Program Gives K For Each X Run
K vs X
Calculated Undulator Parameters:
Keff =
Beff = T
Lambda_rad = e-010 m K X K0
K Shim Data
Measured K value =
Desired K value =
Required field change dB / B = e-002
Required gap change dgap = e-004 m
Beam x motion required dx = e-002 m
(under development)
(prototype) X0
Set the probe position to give the nominal K value.

27. Add Fiducialization Magnets
Need to relate magnetic field to tooling balls.
Yurii Levashov
Attach to undulator ends, measure offsets
LCLS-TN-05-10

28. Move to CMM, Finish Fiducialization
Want D
D1 : Magnetic Measurement
D2 : Calibration
D3 : CMM
D = D1 + D2 + D3

29. Conclusion
Our group’s next big magnetic measurement project is the LCLS.
A new magnetic measurements lab is being built.
We will use Hall probes and coils to tune the undulators.
Long coils will check the first and second field integrals.
High gradient magnets with well defined centers will be used to fiducialize the undulators.
Algorithms are being developed to automate shimming.