1. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 1 LCLS Undulator Tuning And Fiducialization Zack Wolf, Yurii Levashov, Achim Weidemann, Seva Kaplounenko, Scott Jansson, Ralph Colon, Dave Jensen, Scott Anderson

2. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 2 Progress Since Last FAC Progress We have 15 undulators tuned and fiducialized. The MMF temperature control is working well. The reference undulator measurements repeat within spec. The Hall probe calibrations are stable. The Hall probe reference magnet measurements are stable. A study of the stainless steel beam pipe and steel support was made. A study of undulator mounting effects is under way. The undulator quadrupole fiducialization system was commissioned. Challenges Now we need to set K to a specified value. Can’t re-assign slot number. Bad bolts. Machining accuracy of tapered shims. The rough tuning is taking longer than expected. New air compressor still not installed.

3. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 3 Hall Probe Calibrations In Fixed Mount Measurements are made in a reference magnet before the final data set is taken. The Hall probe is calibrated in the same mount it is used in.

4. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 4 Reference Undulator, Reference Magnet within spec temperature? need more studies taken during reference undulator measurements change probe mount (4 undulators tuned, will re-measure) Y. Levashov

5. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 5 Schedule Present Status: 15 undulators tuned and fiducialized 2 in fine tuning 1 in rough tuning 2 deferred for major re-work (bad end magnets, large sag might hit beam pipe) (minor problems like bad bolts or requiring gap shim replacement are fixed as we go) Present Schedule: 17 tuned and fiducialized 1 tuned We are 2 to 4 weeks behind schedule (which is 6 months ahead of installation).

6. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 6 Actions To Help The Schedule Problems Rough tuning is taking a long time Difficult to set K to a specified value (can no longer just re-assign slots) Need to replace bad bolts Need to replace many gap shims (±50 micron strongback tolerance, ±20 micron shim range) Problems with large tapered shim dimension deviations (need to measure shim removed and measure shim replaced) Need to set gap to 4 microns (!) for beam axis to be within ±1 mm of magnetic center (±2 mm good field region) Solutions New gap shimming stand Measure size of removed shim and size of replacement shim Use capacitive sensors for rapid feedback Kugler bench assists with rough tuning when required Coordinate technicians time better (start shimming at 7am) Set K and do phase shimming in one step

7. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 7 Phase Relative To A Reference Wave Is Used To Set Gap And Do Phase Shimming measurement requires alignment of undulator and probe need phase matching shim, not a problem problem after an iteration

8. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 8 Gap Shim, Capacitive Sensor Feedback check gap shimming with capacitive sensors fast, doesn’t require much alignment error shims were replaced at the error locations the removed shims were undersize, the replaced shims were oversize can catch these problems much quicker now

9. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 9 Installed New Gap Adjustment Stand tuning can continue while the technicians adjust the gap can use CMM for feedback on gap adjustment the Kugler bench was used for rough tuning when required

10. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 10 Beampipe Magnetic Effect Study

11. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 11 Undulator Mounting Tests MMFTunnel kinematic mount: well defined, repeatable flat on flat: over-constrained, however, there is compliance in aluminum feet and in the stages, and undulator (?)

12. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 12 Undulator Foot Used For Mounting And Positioning

13. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 13 Issue Under Test Ideal Error in slot for foot Correction Entrance endExit end Move axis to correct height by adjusting foot Twists undulator?, distorts foot? Tooling ball gives axis y position 1 mrad roll tolerance, twist is smaller twist is not the issue Axis at wrong height

14. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 14 Tests Of Mounting Method Differences 0.03 mrad, negligible negligible difference in twist of two undulators tested so far will check on all undulators The undulator appears to sit the same way on flat feet as on the kinematic mount.

15. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 15 To-Do List When we are done with production fix undulators with severe problems (we need to buy more tapered shims) study temperature dependence of K re-measure first five undulators study further undulator handling requirements Other Projects girder alignment plan build quadrupole coils for gun solenoids

16. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 16 Undulator Quadrupole Fiducialization Plan

17. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 17 Undulator Quadrupole Fiducialization System Commissioning Repeatable flip magnet, center position doesn’t change no bias from Earth’s field

18. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 18 Undulator Quadrupole Measurements Scott Anderson will do the fiducialization Andrew Fisher will do the strength and harmonics measurements

19. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 19 Leftovers From Last FAC Hall Probe Position Problem 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!

20. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 20 Solution To The Hall Probe Problem Isaac’s hypothesis: planar Hall effect 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. (30 microns Dover bench, 10 microns Kugler bench)

21. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 21 Undulator Sag Changes Hall Probe Y Position Relative To The Midplane

22. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 22 Effect Of Hall Probe Error On Trajectories y=+200 μm y=+100 μm y=0 μm y=-100 μm y=-200 μm 2 -2 μmμmμmμm 12 6 -2 2 1 -6 2 -14 X TrajectoryY Trajectory

23. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 23 Constant B x0 Corrects B x To Long Coil Field Integral y=+200 μm y=+100 μm y=0 μm y=-100 μm y=-200 μm μmμm -2 12 6 -2 2 1 -6 2 -14 Y TrajectoryCorrected Y Trajectory 2 -2 μmμm B x0 =+0.52 G B x0 =+0.29 G B x0 =0.00 G B x0 =-0.29 G B x0 =-0.63 G

24. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 24 Effect Of Undulator Sag And Hall Probe Error On K Y (μm)K, No B x0 CorrectionK, After Correction ΔK (%), From Correction +2003.4915643.490271-0.037 +1003.4880163.487728-0.0083 03.486728 0.0000 -1003.4878043.487244-0.016 -2003.4916923.489325-0.068 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 much smaller.

25. Zachary Wolf LCLS Undulator Tuningwolf@slac.stanford.edu October 30, 2007 25 Conclusion Production undulator tuning is underway. The lab and equipment are performing well. (But we still need the new air compressor installed.) 15 undulators are tuned and fiducialized. Hall probe calibrations are now stable. Reference undulator measurements are within spec. Reference magnet measurements are stable. The magnetic effect of a stainless steel beam pipe was studied. We are checking that the way the undulator is mounted will not change the fiducialization, and twist can be compensated by a pitch adjustment. We have a quadrupole fiducialization plan. The quadrupole fiducialization system was commissioned. After production, we will fix undulators and continue studies.