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Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 2004
Undulator Fiducialization Test Results
• Fiducialization Tolerances and Procedure• Pointed Magnet Calibration• Two - Point Measurement Algorithm• Hall Probe Center Calibration Results• Summary
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20042
Fiducialization Tolerances
Fiducialization errors are small parts of alignment ones.Magnetic measurement bench will be used for LCLS undulators fiducialization.
Parameter Alignment Value Fiducialization Value Units
Horizontal location tolerance 250 30 µm Vertical location tolerance 50 10 µm
Longitudinal location tolerance 500 50 µm
* - “Magnetic Measurements and Alignment at SLAC” by R. Ruland and Z.Wolf. DOE Review, Aug. 10-12, 2004.
Table 1 *
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20043
Undulator with Pointed Magnets
Extra block of 25 cm in length is between the pointed magnet fixture and the undulator.
The block attached flat to the undulator end plate by screws.
A “tooling ball-bushing” pair is used to locate the magnets with 200µm accuracy.
Position of beam axis with respect to the fiducials p.magnet
Pointed
magnets
Tooling Balls
Tooling Balls
Undulator
Extra Block
Ball – vertical slotBall - Bushing
Granite Table
Probe
X, Y, Z Stage
Top View
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20044
Fiducialization Procedure
Calibrate the pointed magnets on a special stand. Measure magnetic center to tooling ball offset (Measure and tune the undulator.Move the Hall probe into a position which gives a desirable K value.Move the probe along the ideal beam axis to the center of the magnets attached to the undulator. Find the magnetic center of the pointed magnets (zero field point). Measure offset between the undulator axis and the magnetic center (p.magnet ). Measure the position of the pointed magnet tooling balls with respect to the undulator ones on CMM (Apply the offsets to the ideal beam axis.
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20045
Pointed Magnet Calibration
A
B
dD
Magnetic CenterY1 and Y2
Geometrical Center
between tooling balls
A and B
B
A
d
d(Y1 – Y2) / 2Da = D/2 - dDb = D/2 + d
Da
Db
Magnets are placed on a calibration fixture.Hall probe is placed at the magnetic center Y1.
Magnets are rotated 180˚. Hall probe is placed at magnetic center Y2 .d is a difference in the Hall probe positions.D is measured on CMM.
Assumption: Central point will not change its location.Question: How accurate could the magnetic center be found?
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20046
Pointed Magnet Calibration Fixture
Magnets are at 180˚Kinematics’ mount:
3 tooling balls instead of a cap.Two dowel pins instead of V – block2 flat resting pads.
Advantages: Very high surface quality On-shelf parts
Hall probe fixed on a support table.Magnets are moved by X,Y,Z stages.Reliable measurement algorithm has been implemented
216mm
X, Y, Z Stage
Aluminum Plate
Two dowel Pins
Ball restProbe
Tooling Balls
Permanent Magnet
Magnetic Core
Tooling Balls
Stainless Steel Frame
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20047
Why Magnets are not at 90˚?
Magnetic field from one pointed magnet extends far enough to interfere with one from the second. There is no zero field point.
Magnets should have smaller sizes and be set apart at a bigger distance. It involves a different design.
Don’t have a reliable algorithm to implement the 90˚ scheme.
Will continue work on this issue.
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20048
Test Measurement Set-Up
Aluminum table
X, Y, Z
Motorized
Stage
Stage Resolution:
X – 1 mm/step
Y – 1 mm/step
Z – 20 mm/step
Aluminum Bracket
Aluminum Support
Group 3 Hall Probe
Pointed magnet Fixture
7 mm
40 cm10 cm
ZXY
Difference in thermal coefficients causes in Y positioning errors: ~ 5µm / ˚C. ( Will be not a case in new Lab.) Magnets misalignment: ~ 300µm in X and ~ 150µm in Z.
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 20049
Two - Point Measurement Algorithm1. Start position is unknown. It
is randomly chosen with ± 200 µm (cube).
2. Move in Y by 1.8 mm toward the first magnet.
3. Scan in Z, then in X.4. Find maximums by
polynomial interpolation.5. Move back in Y by 1.8mm.6. Scan in Y.7. Find a minimum by linear fit.8. Repeat steps 2 – 7 for the
second magnet.9. Calculate magnetic center
position.
Advantage: Information about misalignment of the magnets.
1 1.5 2 2.5 3 3.5 4 4.5 50
5
10
15
20
25
30
35
B(Xb, Yb, Zb)A(Xa, Ya, Za)
Xo = (Xa + Xb) / 2
Yo = (Ya + Yb) / 2
Zo = (Za + Zb) / 2
N
N
0Zero field line
ZXY
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 200410
Hall Probe Center Calibration Results
Group 3 Hall Probe # 01231177Std. X = 5µm
Std. Y < 1µmZeroes in Z (Stage resolution)T ≈ 0.1 ˚C ≈ 4.5 minutes/run
0 5 10 15 20 25 30-15
-10
-5
0
5
10
15 Probe zero positioning.
Run number
Po
sit
ion
in
µm
X - direction
Y - direction
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 200411
Temperature Effect on Y Measurements
Group 3 Hall Probe # 01231177Std. X = 3.4µm
Std. Y < 1µm (Trend)
T = 1.2 ˚C Slope of 6µm / ˚C is in a good agreement with our estimation.
No temperature effect on X positioning
0 5 10 15 20-15
-10
-5
0
5
10
15
Run Number
Po
sit
ion
in
µm
X - direction
Y - direction
Trend line
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 200412
Effect of Steel Plate on Magnetic Center Location
18cm x 18cm steel plate Group 3 Hall Probe
# 01231177 Magnets at 180˚ Minimum distance -
25cm
0 5 10 15 20 25 30-20
-15
-10
-5
0
5
10
15
20
Distance from steel plate in cm
Po
sit
ion
in
µm
No Steel plate
Yurii Levashov
Undulator fiducialization test results [email protected]
Oct. 14, 200413
Summary
Fiducialization procedure is close to be finalized.Calibration fixture based on pointed magnets technique has been developed. Work on the calibration fixture will be done soon.Two-point calibration algorithm has been proposed and tested to be adequate. Magnet misalignment of ± 200 µm has not affect on results of the calibration.Accuracy of locating the pointed magnet center is:
1 µm in Y; 5 µm in X; 20 µm in Z (stage resolution).
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