1. LCLS Undulator Tuning And Fiducialization
Zack Wolf, Yurii Levashov,
Achim Weidemann, Seva Kaplounenko,
Andrew Fisher, Dave Jensen

2. Progress Since Last Lehman Review
We are in production now!
Twelve undulators have measurement results.
Eight undulators are tuned and fiducialized.
Progress Highlights
Our Hall probe and Kugler bench electrical noise problems are solved.
We wrote a test plan: LCLS-TN-06-17
We wrote a fiducialization plan: LCLS-TN-07-02
We were educated on planar Hall effects.
We checked our software results with Heinz-Dieter’s results.
Our Hall probe calibrations are stable (finally).
We started a series of Hall probe checks in a reference magnet.
Our field integral measurement system has been tested: LCLS-TN-07-03
Our production rate is approximately 1 per week, if things go well.

3. Hall Probe Noise Noise ~4 G Noise ~0.2 G The Senis probe did not work.
We are only using Sentron probes.
We own one Sentron probe and borrowed one from Isaac.
We are having two custom Sentron probes made for us.

4. Kugler Bench Noise Noise ~0.2 mV Noise ~0.03 mV
Dover bench uses linear motor driver.
Kugler bench uses chopped motor driver.
Problem solved by adding heavy filtering to the Kugler motor lines.

5. Undulator Test Plan LCLS-TN-06-17 Gives requirements
Describes equipment
Enumerates each step of tuning
Describes output data

6. Undulator Fiducialization Plan
LCLS-TN-07-02
Gives requirements
Describes equipment
Describes methods
Describes checks
Enumerates each step of fiducialization
Describes output data

7. Tuning Bench Fiducialization Checks
Reference fiducialization magnets
Optical alignment check
Optical fiducialization check

8. CMM Fiducialization Checks

9. Hall Probe Position Problem
The vertical trajectories on the
Dover bench and Kugler bench
did not agree.
The horizontal field integrals from
the Hall probe had a large y
dependence. Coil measurements
showed no such dependence.
We stumbled onto a paper Isaac
wrote in 1997!
The Sentron probes are sensitive
to planar Hall effects after all!

10. Solution To The Hall Probe Problem
Isaac’s hypothesis:
planar Hall effect
(30 microns Dover bench,
10 microns Kugler bench)
Solution:
Measure the positions of the Hall elements.
Tune the horizontal trajectory with the By probe on the midplane.
Tune the vertical trajectory with the Bx probe on the midplane.
Use only the long coil for final field integral measurements.

11. Undulator Sag Changes Hall Probe Y Position Relative To The Midplane

12. Effect Of Hall Probe Error On Trajectoriesμm
X Trajectory μm
Y Trajectory 2 12
y=+200 μm -2 -2 6
y=+100 μm -1 2
y=0 μm -2 1
y=-100 μm -6 2
y=-200 μm
-14

13. Constant Bx0 Corrects Bx To Long Coil Field Integralμm
Y Trajectory μm
Corrected Y Trajectory 12 2
y=+200 μm
Bx0=+0.52 G -2 -2 6
y=+100 μm
Bx0=+0.29 G -1 2
y=0 μm
Bx0=0.00 G -2 1
y=-100 μm
Bx0=-0.29 G -6 2
y=-200 μm
Bx0=-0.63 G
-14

14. Effect Of Undulator Sag And Hall Probe Error On K
Y (μm)
K, No Bx0 Correction
K, After Correction
ΔK (%), From Correction
+200
-0.037
+100
0.0000
-100
-0.016
-200
-0.068
Conclusion:
The trajectory curvature caused by the Hall probe error when the undulator
sags by 100 microns will change K by less than 0.016% if no correction is
applied. We do apply a correction, making the effect very small.

15. Software Checks Software bug check:
We compared our analysis results to Heinz-Dieters’.
We also compared to ANL’s software. The details
of the ANL code need to be investigated further
(average trajectory slope removed in K calculation?, …).
SN 03, Run 44
Conclusion: OK

16. Hall Probe Calibration Problem
Probe temperature?
Poor fits?
Probe offset?
Calibration magnet
non-uniformity?
Impurities in copper
probe chiller?
Calibration Change
Before and after first undulator

17. Calibration Magnet
0.25 G
Very uniform!
2.2 G
0.2 G

18. Hall Probe Calibration Study Problem
G-10
Temperature, ok
Fits, ok
Calibration magnet uniform
Copper non-magnetic
Offsets change, why?
G-10, permanent mount
Copper block
Stress on probe

19. Hall Probe Calibrations In Fixed Mount
Only
and
are used
so far.
The Hall probe is
calibrated in the
same mount it is
used in.
Starting measurements in reference magnet before set K

20. Field Integrals

21. Field Integral Checks, Fluxgate Probe
Long Coil

22. Field Integral Checks, Short Magnet
Calculated
~6%
Measured

23. Check The Magnetic Effect Of The Beam Pipe
We are helping ANL study
whether the stainless steel
beam pipe affects
the magnetic fields in the
undulators.
We are in the process of
determining whether the effect
is different at shim locations.
We will test the steel support
for the beam pipe.
Andrew Fisher

24. The Stainless Steel Beam Pipe Is Magnetic
Vertical beam pipe section with permanent magnet stuck to it.

25. Hall Probe Measurements In The Beam Pipe
Fit peaks.
Compare peaks
with and without
the beam pipe.

26. Effect Of Beam Pipe, No Shims
Measurement made with
three scans.
1) No beam pipe.
2) No beam pipe.
Use difference 2-1 to
calculate error bars.
3) With beam pipe.
Absolute value of
difference 3-2 plotted with
error bars from 2-1.
Each scan takes 8 minutes.

27. Effect Of Beam Pipe On Phase Shim
Result needs to be verified by ANL.

28. Possible Mechanical Effect?, No

29. Open Issues (Some of which we are working on)
Pole to pole variations in change from beam pipe
(effect on trajectories, phase, field integrals, …)
Need to figure out how to measure Bx
(Do our Bx shims change?)
Need to study effect on By shims
Need to study the effect of the steel beam pipe support structure
Need to correlate mu changes to field changes
Can we measure enough to know what the beam pipe does? No.

30. Aluminum Beam Pipe From Rodd Pope No absolute value. Scale same as
stainless steel
for comparison.
No Effect

31. Aluminum Beam Pipe And Phase Shim
No Effect

32. Conclusion Our noise problems are solved. We have a written test plan.
We have a written fiducialization plan.
We solved the planar Hall effect problem.
The undulator sag plus planar Hall effect does not spoil K.
We checked our software and found no bugs.
Our Hall probe calibrations are looking good now.
We check our Hall probe frequently in a reference magnet.
Our field integral measurement system is working well.
We demonstrated 1 undulator per week when there are no problems.
We are assisting in the study of the magnetic effects of the beam pipe.