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

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 = 13.64 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 = 1.249 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

LCLS Location J. Galayda

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

Magnetic Measurement Facility Undulator Tuning Magnetic Measurement Facility

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

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

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

Rough Tuning Bench Components

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

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

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

Gap Shims Tapered Shim ANL TB-48

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

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

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

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

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

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

Fine Tuning Bench Components

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

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

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

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

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 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

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

Fiducialization

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

Schedule Robert Ruland

Quadrupole Fiducialization System LCLS-TN-05-11

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

Detector Signal vs Quad Position

Pitch and Yaw Measurements

Quadrupole Fiducialization Schematic System Overview Wire Vibration Sensor Wire Finder

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.