Transcript Undulator Fiducialization Test Results

Undulator Fiducialization Test Results
Fiducialization Tolerances and Procedure
Pointed Magnet Calibration
Two - Point Measurement Algorithm
Hall Probe Center Calibration Results
Summary
Oct. 14, 2004
Undulator fiducialization test results
Yurii Levashov
[email protected]
Fiducialization Tolerances
Table 1 *
Parameter
Alignment Value
Fiducialization Value
Units
Horizontal location tolerance
250
30
Vertical location tolerance
50
10
µm
Longitudinal location tolerance
500
50
µm
µm
Fiducialization errors are small parts of alignment ones.
Magnetic measurement bench will be used for LCLS undulators
fiducialization.
* - “Magnetic Measurements and Alignment at SLAC” by R. Ruland and Z.Wolf. DOE Review, Aug. 10-12, 2004.
Oct. 14, 2004
Undulator fiducialization test results
2
Yurii Levashov
[email protected]
Undulator with Pointed Magnets
D2
Tooling Balls
D0
Undulator
D1
Pointed
magnets
Tooling Balls
Ball – vertical slot
Ball - Bushing
Extra Block
Top View
Probe
X, Y, Z Stage
Granite Table
Oct. 14, 2004
Undulator fiducialization test results
3
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
D0= Dp.magnet + D1+ D2
Yurii Levashov
[email protected]
Fiducialization Procedure
Calibrate the pointed magnets on a special stand. Measure
magnetic center to tooling ball offset (D1).
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 (Dp.magnet ).
Measure the position of the pointed magnet tooling balls
with respect to the undulator ones on CMM (D2).
Apply the offsets to the ideal beam axis.
Oct. 14, 2004
Undulator fiducialization test results
4
Yurii Levashov
[email protected]
Pointed Magnet Calibration
B
A
Magnetic Center
Y1 and Y2
D
Db
d
2d
B
Geometrical Center
between tooling balls
A and B
d = (Y1 – Y2) / 2
Da = D/2 - d
Db = D/2 + d
Da
A
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 .
2d 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?
Oct. 14, 2004
Undulator fiducialization test results
5
Yurii Levashov
[email protected]
Pointed Magnet Calibration Fixture
Tooling Balls
Permanent Magnet
216mm
Magnetic Core
Stainless Steel Frame
Ball rest
Probe
Two dowel Pins
Tooling Balls
Aluminum Plate
Magnets are at 180˚
Kinematics’ mount:
3 tooling balls instead of
a cap.
Two dowel pins instead of
V – block
2 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
X, Y, Z Stage
Oct. 14, 2004
Undulator fiducialization test results
6
Yurii Levashov
[email protected]
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.
Oct. 14, 2004
Undulator fiducialization test results
7
Yurii Levashov
[email protected]
Test Measurement Set-Up
Aluminum Bracket
Pointed magnet Fixture
Group 3 Hall Probe
X, Y, Z
Motorized
Stage
7 mm
Aluminum Support
10 cm
Stage Resolution:
X – 1 mm/step
Y – 1 mm/step
Z – 20 mm/step
Y X
40 cm
Z
Aluminum table
Difference in thermal coefficients causes in Y positioning errors:
( Will be not a case in new Lab.)
Magnets misalignment: ~ 300µm in X and ~ 150µm in Z.
Oct. 14, 2004
Undulator fiducialization test results
8
~ 5µm / ˚C.
Yurii Levashov
[email protected]
Two - Point Measurement Algorithm
N
1.
2.
3.
4.
Zero field line
0
A(Xa, Ya, Za)
35
Y X

30

25

B(Xb, Yb, Zb)
Z
Xo = (Xa + Xb) / 2
Yo = (Ya + Yb) / 2
Zo = (Za + Zb) / 2


20


15


10
9.
5
0
1
1.5
2
2.5
3
3.5
4
4.5
5.
6.
7.
8.
5
Start position is unknown. It
is randomly chosen with
± 200 µm (cube).
Move in Y by 1.8 mm
toward the first magnet.
Scan in Z, then in X.
Find maximums by
polynomial interpolation.
Move back in Y by 1.8mm.
Scan in Y.
Find a minimum by linear fit.
Repeat steps 2 – 7 for the
second magnet.
Calculate magnetic center
position.
N
Advantage: Information about misalignment of the magnets.
Oct. 14, 2004
Undulator fiducialization test results
9
Yurii Levashov
[email protected]
Hall Probe
Center Calibration Results
Probe zero positioning.
15
10
Group 3 Hall
Probe # 01231177
Std. X = 5µm
Std. Y < 1µm
Zeroes in Z (Stage
resolution)
DT ≈ 0.1 ˚C
≈ 4.5 minutes/run
Position in µm
5
0
-5
-10
X - dire ction
Y - dire ction
-15
0
5
10
15
Run number
Oct. 14, 2004
Undulator fiducialization test results
20
25
10
30
Yurii Levashov
[email protected]
Temperature Effect on Y Measurements
15
Group 3 Hall Probe
# 01231177
Std. X = 3.4µm
Std. Y < 1µm (Trend)
DT = 1.2 ˚C
Slope of 6µm / ˚C is
in a good agreement
with our estimation.
No temperature
effect on X
positioning
10
Position in µm
5
0
-5
X - direction
Y - direction
Trend line
-10
-15
0
5
10
Run Number
Oct. 14, 2004
Undulator fiducialization test results
15
11
20
Yurii Levashov
[email protected]
Effect of Steel Plate on Magnetic Center Location
20
15
Position in µm
10
5
18cm x 18cm steel plate
Group 3 Hall Probe
# 01231177
Magnets at 180˚
Minimum distance 25cm
0
-5
-10
-15
No Steel plate
-20
0
5
10
15
20
Distance from steel plate in cm
Oct. 14, 2004
Undulator fiducialization test results
12
25
30
Yurii Levashov
[email protected]
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).
Oct. 14, 2004
Undulator fiducialization test results
13
Yurii Levashov
[email protected]