zachary wolf lcls undulator [email protected] october 30, 2007 1 lcls undulator tuning...
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Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20071
LCLS Undulator TuningAnd Fiducialization
Zack Wolf, Yurii Levashov,
Achim Weidemann, Seva Kaplounenko,
Scott Jansson, Ralph Colon,
Dave Jensen, Scott Anderson
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20072
Progress Since Last FAC
ProgressWe 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.
ChallengesNow 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.
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20073
Hall Probe Calibrations In Fixed Mount
Measurements are made in a reference magnet beforethe final data set is taken.
The Hall probe iscalibrated in the same mount it isused in.
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20074
Reference Undulator, Reference Magnet
within spec
temperature?need more studies
taken during referenceundulator measurements
change probemount
(4 undulators tuned,will re-measure)
Y. Levashov
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20075
SchedulePresent Status:15 undulators tuned and fiducialized2 in fine tuning1 in rough tuning2 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 fiducialized1 tuned
We are 2 to 4 weeks behind schedule (which is 6 months ahead of installation).
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20076
Actions To Help The ScheduleProblemsRough tuning is taking a long timeDifficult to set K to a specified value (can no longer just re-assign slots)Need to replace bad boltsNeed 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) SolutionsNew gap shimming standMeasure size of removed shim and size of replacement shimUse capacitive sensors for rapid feedbackKugler bench assists with rough tuning when requiredCoordinate technicians time better (start shimming at 7am)Set K and do phase shimming in one step
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20077
Phase Relative To A Reference WaveIs Used To Set Gap And Do Phase Shimming
measurementrequires alignment ofundulator andprobe
need phasematching shim,not a problem
problem
problem
problem
after an iteration
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20078
Gap Shim, Capacitive Sensor Feedback
check gapshimming withcapacitivesensors
fast,doesn’trequire muchalignment
errorerror
error
shims werereplaced atthe error locations
the removedshims wereundersize,the replacedshims wereoversize
can catch these problems much quicker now
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 20079
Installed New Gap Adjustment Stand
tuning cancontinuewhile thetechniciansadjust the gap
can use CMMfor feedbackon gapadjustment
the Kuglerbench was usedfor rough tuningwhen required
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200710
Beampipe Magnetic Effect Study
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200711
Undulator Mounting Tests
MMF Tunnel
kinematic mount:well defined,repeatable
flat on flat:over-constrained, however, thereis compliance in aluminum feetand in the stages, and undulator (?)
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200712
Undulator FootUsed For Mounting And Positioning
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200713
Issue Under Test
Ideal Error inslot for foot
Correction
Entrance end Exit end
Move axisto correctheight by
adjusting foot
Twists undulator?,distorts foot?
Tooling ball gives axis y position
1 mradroll tolerance,twist is smaller
twist is not the issue
Axis at wrongheight
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200714
Tests Of Mounting Method Differences
0.03 mrad,negligible
negligible difference in twist of two undulators tested so farwill check on all undulators
The undulatorappears tosit the sameway on flatfeet as on thekinematicmount.
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200715
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
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200716
Undulator Quadrupole Fiducialization Plan
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200717
Undulator Quadrupole FiducializationSystem Commissioning
Repeatable
flip magnet,center position doesn’t changeno bias from Earth’s field
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200718
Undulator Quadrupole Measurements
Scott Andersonwill do the fiducialization
Andrew Fisherwill do the strength
and harmonics measurements
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200719
Leftovers From Last FACHall 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 Isaacwrote in 1997!
The Sentron probes are sensitiveto planar Hall effects after all!
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200720
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)
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200721
Undulator Sag Changes Hall Probe Y Position Relative To The Midplane
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200722
Effect Of Hall Probe Error On Trajectories
y=+200 μm
y=+100 μm
y=0 μm
y=-100 μm
y=-200 μm
2
-2
μm μm
-2
12
-1
6
-2
2
1
-6
2
-14
X Trajectory Y Trajectory
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200723
Constant Bx0 Corrects Bx To Long Coil Field Integral
y=+200 μm
y=+100 μm
y=0 μm
y=-100 μm
y=-200 μm
μm
-2
12
-1
6
-2
2
1
-6
2
-14
Y Trajectory Corrected Y Trajectory2
-2
μm
Bx0=+0.52 G
Bx0=+0.29 G
Bx0=0.00 G
Bx0=-0.29 G
Bx0=-0.63 G
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200724
Effect Of Undulator Sag And Hall Probe Error On K
Y (μm) K, No Bx0 Correction K, After CorrectionΔK (%), From
Correction
+200 3.491564 3.490271 -0.037
+100 3.488016 3.487728 -0.0083
0 3.486728 3.486728 0.0000
-100 3.487804 3.487244 -0.016
-200 3.491692 3.489325 -0.068
Conclusion:The trajectory curvature caused by the Hall probe error when the undulatorsags by 100 microns will change K by less than 0.016% if no correction isapplied. We do apply a correction, making the effect much smaller.
Zachary Wolf
LCLS Undulator Tuning [email protected]
October 30, 200725
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.