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LCLS Undulator Magnetic MeasurementsPowerPoint Presentation

LCLS Undulator Magnetic Measurements

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### LCLS UndulatorMagnetic Measurements

Zack Wolf,

Scott Anderson, Ralph Colon, Brendan Dix, Scott Jansson, Dave Jensen, Luis Juarez,

Seva Kaplounenko, Yurii Levashov,

Wei Wang, Achim Weidemann

Undulator Tuning, General Approach

- Use ANL and DESY experience
- Techniques have been developed at ANL and DESY which work very well.
- We will use the best of the ANL and DESY measurement techniques as our starting point (both have been very generous in sharing with us).

- We need to adapt for production measurements.

SLAC 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

Important Dates

(Approximate)

MMF Major Construction Finished Feb. 17, 2006

MMF Beneficial Occupancy March 6, 2006

Kugler Bench Complete April 15, 2006

Kugler Bench At SLAC May 15, 2006

Kugler Bench Handover To SLAC June 15, 2006

1st Article Arrives At SLAC July 2, 2006

MMF Ready For Measurements July 28, 2006

Production Measurements Start August 29, 2006

Undulator Measurement Benches

Goal: Move probes along a very straight line through the undulator.

ANL Bench

DESY Bench

LCLS-TN-03-7

Kugler Bench

On order, expected at SLAC May 15, 2006. Ready for use June 15, 2006.

SLAC Software Development Bench

(While we wait

on the Kugler

bench)

Bench software by Seva Kaplounenko

Undulator Measurement Steps

- Place undulator
- Mechanically align undulator to bench
- Magnetically align Hall probe to undulator
- Perform any required large gap adjustments and re-align
- Straighten the X and Y trajectories
- Minimize phase errors
- Perform phase matching
- Determine K vs X, move probe to the X value which gives the specified K
- Add fiducialization magnets to undulator ends, locate center of fiducialization magnets
- Move undulator to CMM, finish fiducialization

LCLS-TN-03-7

1) Place Undulator

Ben Poling placing the ANL prototype on the SLAC prototype bench 12/9/05.

Place Undulator

Bearing

SLAC CAM Movers

Cam

Potentiometer

Bearing

Harmonic

Drive

Motor

Brake

Built by Gordon Bowden, Yurii Levashov, Scott Jansson

2) Mechanically Align to Bench

Use Capacitive Sensors

Yurii Levashov

We tested capacitive sensors in TTF undulators at DESY

2) Mechanically Align To Bench

Undulator aligned to fixed height of reference pole.

2) Mechanically Align to Bench

Previous experience from PEP II and SPEAR III

- Use 6 capacitive sensors on an arm
- Gives x, yaw, y, pitch, and roll
- Have reference poles at each end
- Calibrate sensors with micrometers

By

By

y

x

3) Magnetically Align Hall Probey

x

- Technique
- Every N’th pole, move probe vertically,
find minimum

- Every N’th pole, move probe horizontally,
find midpoint between edges

- Plot (x, y) vs z, fit for magnetic alignment

- Every N’th pole, move probe vertically,

3) Magnetically Align Hall Probe

SLAC Measurements

5) Straighten X And Y Trajectories

Simultaneously measure

Bx and By (Hall)

and Bx from a coil

LCLS-TN-05-5

5) Straighten X And Y Trajectories

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
- Developing software to try to automate shim placement

LCLS-TN-04-7

5) Straighten X And Y Trajectories

Measured

X

Trajectory

Calculate

Shims

Modeled

X Traj

With

Calc

Shims

Measured

X Traj

After Calc

Shims

Applied

Automate Shimming, Under Development

5) Earth’s Field

LCLS-TN-05-4

- We will either
- Measure the field integrals and shim in the tunnel
- Put a mu-metal shield around the undulators (Isaac Vasserman)

6) Minimize Phase Errors

- A magnet which is too strong can cause phase errors.
- The trajectory is shifted, but there is no residual slope.
- Correct with phase shims.

Poles 51 and 52 are 1% too strong.

LCLS-TN-04-7

Measured

Phase

Errors

Calculated

Shims

Under development

6) Minimize Phase Errors

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
- Developing 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

7) Phase Matching

pi

pi/2

pi/2

(mod 2pi)

Program provides shim information

Phase Matching Shim Data

Entrance:

Number of end poles = 5

Measured Phase At The Entrance Poles:

(Phase = 0 at the entrance cell boundary.)

Pole Number = 1 2 3 4 5 6

Phase (deg) = 393.80 436.28 624.41 811.05 986.83 1157.97

Expected phase at pole number 6 = 1170.00 deg

Entrance phase error (from pole 6) = -12.03 deg

Entrance phase match shim dimension = 0.0000e+000 m

(under development)

K0

K

X

8) Determine K vs XSinusoidal Field

Canted Poles

LCLS-TN-04-7

Analysis Program Gives K For Each X Run

K vs X

Calculated Undulator Parameters:

Keff = 3.627747

Beff = 1.295076 T

Lambda_rad = 1.595811e-010 m

K Shim Data

Measured K value = 3.627747

Desired K value = 3.500000

Required field change dB / B = -3.6499e-002

Required gap change dgap = 2.1330e-004 m

Beam x motion required dx = 4.7401e-002 m

(under development)

(prototype)

X0

Set the probe position to give the nominal K value.

9) Add Fiducialization Magnets

Need to relate magnetic field to tooling balls.

Yurii Levashov

Attach to undulator ends, measure offsets

LCLS-TN-05-10

10) Move to CMM, Finish Fiducialization

Want D

D1 : Magnetic Measurement

D2 : Calibration

D3 : CMM

D = D1 + D2 + D3

Conclusion

- Our group’s next big magnetic measurement project is the LCLS.
- A new magnetic measurements lab is being built.
- We will use Hall probes and coils to tune the undulators.
- Long coils will check the first and second field integrals.
- High gradient magnets with well defined centers will be used to fiducialize the undulators.
- Algorithms are being developed to automate shimming.

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