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LCLS Undulator Tuning And Fiducialization

Detailed progress report on undulator tuning, fiducialization plans, Hall probe calibrations, software checks, and field integral measurements at LCLS. Includes solutions to hall probe position problems and effects of undulator sag on trajectories.

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LCLS Undulator Tuning And Fiducialization

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  1. LCLS Undulator TuningAnd 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 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 Trajectories μm μm X Trajectory 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 Integral μm 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 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 CalibrationStudy 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 03-16-07 and 04-03-07 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 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.

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