Transcript Undulator Prototype Status

Undulator Prototype
Status and Plans
Marion M. White APS-ASD
Argonne National Laboratory
Office of Science
U.S. Department of Energy
A U.S. Department of Energy
Office of Science Laboratory
Operated by The University of Chicago
Outline – Prototype Undulator Status
• Design Challenges
• Mechanical Design Features
• Performance
• Improvements
• Canted Pole Undulator Measurements
• Plans
• Summary
2
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Undulator Design Parameters
Parameter
Specified Value
Undulator Type
Magnet Material
Planar Hybrid
NdFeB
Pole Material
Vanadium Permendur
Pole Gap (Min. Allowance) 6 mm
Period Length
30 mm
Effective Magnetic Field
1.296 Tesla
Effective K Value
3.63
Undulator Segment Length 3.40 m
Nr. of Undulator Segments 33
3
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
LCLS – Familiar Design Challenges
Between APS insertion devices and the LEUTL FEL,
the APS team has a lot of undulator experience with:
• High-quality undulator magnetic fields
• Magnetic tuning for phase errors and trajectory
•
•
•
Pioneering
Science and
Technology
straightness
Variable and fixed gaps
Phasing undulator ends
Magnetic design
- NdFeB magnets
- Vanadium permendur poles
- 30-mm period
- K=3.63 so Beff=1.296 T
4
Office of Science
U.S. Department
of Energy
Magnetic Design
Standard undulator design considerations:
• Maximize the field
• Don’t demagnetize the magnets
• Don’t oversaturate the poles
5
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Magnetic Design (2)
Prevent Radiation Damage
- Chose a new grade of magnet with higher
coercivity (N39SH) for the prototype
- Attention to minimizing the demagnetizing field
- Design goal to be as restrictive as usual on the
demagnetizing field, maybe even at the cost of
higher pole saturation, then use the high Hc
magnets
6
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
New Challenges – Uniformity and Stability
Achieving a field-strength uniformity of 1.5 x 10-4
along the undulator line is a challenge
-
Gap change of 1.4 microns
Vertical shift ~ 50 microns
Temperature coefficient of the magnet is 0.1%/°C
Thermal expansion
And there may be a desire to taper in the future
7
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Outline – Prototype Undulator Status
•
Design Challenges
• Mechanical Design Features
• Performance
• Design Improvements
• Canted Pole Measurements
• Plans
• Summary
8
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Complete Undulator Module
Quadrupole
Rails
Magnet Assembly
CAM Movers
BPM
Cradle
9
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Mechanical Design
10
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Mechanical Design Features
1. Housing is made from a forged Ti bar
2. Ti was preferred over other materials
because:
•
Nonmagnetic
•
Low thermal expansion
•
Long-term stability
•
Rigidity to density ratio for minimal
deflection
3. Al baseplate provides partial thermal
compensation
4. Open on one side for magnetic
measurement access and shimming
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
11
Titanium Strongback
12
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Mechanical design features, cont.
Shims and push-pull
screws adjust the gap.
Magnets are clamped
from only one side.
Magnetic side shims.
Steel bars approach side
of pole. Correction up to
~3% in field.
13
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Pole clamping
Poles have titanium wings, and
are clamped on both sides
14
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Pole simplification now under consideration
Eliminate the wings
and screw the pole
in from the bottom.
Still being refined;
will be used in a
segment of the
prototype and
reviewed.
15
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
End-phase adjusters in the prototype
•Piezo translators on end sections
allowed gap & field strength
adjustment
•Over the last seven periods only
•Adjusted phasing between
undulators
•Can relax the requirement for
constant Beff between undulators to
7x10-4
•Travel range 100 micron each jaw
(200 microns in total gap). 100
microns corresponds to 29°.
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
16
Eccentric cam movers
Each cam is driven by a separate motor
Adjustable in both transverse directions & in roll, pitch, & yaw
17
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Outline – Prototype Undulator Status
•
•
Design Challenges
Mechanical Design Features
• Performance
• Design Improvements
• Canted Pole Measurements
• Plans
• Summary
18
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Assembly - Magnet Sorting
Single Magnets
Matched Pairs
Magnets were sorted by strength (Total Moment), then the
strongest and the weakest were matched together.
Very important – saved lots of time since we found we
could use this vendor’s measurements “as is” for sorting;
not all vendors routinely make these measurements.
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
19
Assembly - pole sorting
After magnet sorting, the main contributor to field errors
was pole height variation.
Tall and short poles were paired, and RMS deviation in gap
was reduced from 6.3 to 2.4 microns
But this pairing
neglected the
contribution of the Al
base plate thickness,
and variation due to
the attachment to the
Ti. Final gap variation
was ±50 microns.
After sorting:
Note – Put tighter tolerances on the Al baseplate for production
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
20
Magnetic Tuning
Nonetheless, the device met the trajectory straightness
requirement (±2 micron) without tuning.
After tuning, the wiggle-averaged trajectory was within a
range of about 0.5 microns.
21
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Phase Error Tuning
The calculated spontaneous emission amplitude needed
tuning to raise it from 93% to over 99% of ideal.
(The rms phase error decreased from 11.2° to 6.5°.)
22
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Temperature Dependence
Care must be taken in the measurements to allow the
undulator sufficient thermal equilibration time
Also need to correct for temperature dependence of the Hall
probe: (DBeff/Beff)/DT = -5.5 x 10-4 /°C
23
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Outline – Prototype Undulator Status
• Design Challenges
• Mechanical Design Features
• Performance
• Post-Prototype Design Improvements
• Canted Pole Measurements
• Plans
• Summary
24
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Post-prototype Considerations
•
End phase adjustments
- Piezos long-term stability for this application is untested
•
Adjustment to final gap has not yet been done, but can
do this with the cant anyway.
•
Assume temperature dependence is handled by the
conventional facilities specifications.
25
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Radiation Damage – Post-prototype
•
•
•
•
Had considered using SmCo magnets
- Better radiation resistance
- Smaller decrease in strength with temperature rise
- But overall weaker strength and more brittle
- Ruled out based on schedule – no time for R&D.
Instead, take advantage of APS radiation exposure and
damage experience at the APS.
Provide dose limit guidance and information to SLAC to
be used as input into the undulator protection system.
Do not operate LCLS under conditions likely to
result in damage to the undulators.
26
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Post-prototype, cont.
•
•
•
A comb shunt for adjusting the field strength was proposed
Initial tests look promising, but added design complexity;
(remote capability - considerable added design complexity)
Also a possibility for end phase correction only
27
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Outline – Prototype Undulator Status
• Design Challenges
• Mechanical Design Features
• Performance
• Post-Prototype Design Improvements
• Canted Pole Measurements
• Plans
• Summary
28
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Canting The Gap
•
A scheme ( thanks to J. Pflueger) of canting the poles so
that field strength varies with lateral (horizontal) position
was very promising.
•
A test section was “canted” and measured with excellent
results. Canting was adopted into the baseline.
29
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Canted Cross-section (exaggerated)
LCLS
Undulator
CrossSection with
Wedged
Shims
30
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Effective Magnetic Field
• Measured slope of 6.6 Gauss/mm agrees with calculations
•
(~ 5.7 Gauss/mm for 3 mrad cant).
Alignment accuracy needed for DB/B ~ 1.5x10-4 ~ 2 Gauss -> 0.3 mm
31
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
RMS Phase Error
•
•
No significant dependency on X
An RMS phase error of ~ 6.5 degree is an upper limit for
near-perfect (~100%) performance.
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
32
Horizontal Trajectory (averaged over period
length) at 14.1 GeV
•
•
Trajectory vs. X well behaved and well within the tolerance
requirement of 2 mm maximum walk-off from a straight line.
Operational range is ±1.2 mm for ±1.0°C temperature
compensation.
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
33
Fringe Fields at X=65 and 100 mm
•
Fringe fields with new shims are close to earth field
for X=100 mm. (Earth field contribution to trajectory
shift has to be corrected.)
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
34
Fine adjustment of effective magnetic field
(Isaac’s field-tuning procedure )
1. Select spacers with thickness step ~ 15 µm to set the
effective field in the range of ±30 Gauss (1 µm in gap
corresponds to ~ 2 Gauss in field).
2. Set spacer horizontal position to adjust the effective field to
~ ±6 Gauss (spacers are wedged with 3 mm/mm cant)
3. Set horizontal position of the undulator as a whole so the
effective field is in the range ±2 Gauss (DB/B ~ ±1.5x10-4)
(This step saves time and provides better accuracy)
4. The undulator horizontal position could be remotely
controlled during operation to compensate for in-tunnel
temperature variations (motion of ±1.2 mm for ±1°C
needed). Such option is available, if quadrupoles are
separated from undulator sections.
35
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Magnetic needles for alignment
• Only one needle is required for alignment in the X direction
• One more needle has to be added at Y=0 for alignment in the Y
direction
Pioneering
Science and
Technology
36
Office of Science
U.S. Department
of Energy
Outline – Prototype Undulator Status
• Design Challenges
• Mechanical Design Features
• Performance
• Post-Prototype Design Improvements
• Canted Pole Measurements
• Plans
•
Summary
37
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Scope and Plans – Undulator Systems
• 33 Precision magnetic arrays with canted poles
• 33 Support/alignment systems including:
•
•
- Cradle that supports the undulator, BPM, and
quadrupole magnet.
- Precision CAM movers and motors enabling
positioning, alignment, and adjustment of the cradle.
- Rail system to move the undulator, facilitating manual
retraction of an undulator out of the beamline and
precision reproducible re-insertion.
7 Spare Undulator Modules
1 Undulator Transport Device for Installation
38
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Plan – Undulators (1)
•
•
To meet schedule and funding profiles, and to ensure
that the Undulator Systems are complete by July
2007, we plan to procure the following long-lead items
as early as possible in FY05:
- Precision-machined titanium strongbacks
- NdFeB Magnet blocks
- Vanadium Permendur Magnet poles
The same APS undulator experts, who were relied
upon for design, construction, and assessment of the
prototype, will finalize procurement packages for the
LL items, in accordance with our Advance
Procurement Plans [APP].
39
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Scope – Quadrupole Magnet Systems
•
33 Quadrupole Magnet Systems - installed
- Permanent Magnet Quadrupole
- Support with Precision Translator [settable to 5 um;
readout to 1um]
•
5 Spare Magnet Systems
•
Separate steering is not included
40
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Summary
•
•
•
•
•
A full-scale prototype undulator was constructed and
tested at APS, and met LCLS performance goals.
A subsequent design improvement, that of introducing a 3mrad cant in the pole gap, was implemented using wedged
spacers between the aluminum base plates and the titanium
core. It was successfully tested and the concept was adopted
in the baseline.
A disadvantage of the canted-pole design is the necessity to
provide a separate support for vacuum chamber
Magnetic measurements show good agreement with
calculated change of the effective magnetic field versus X
(horizontal motion).
No significant change of the RMS phase error versus X was
41
measured.
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy
Current Status
• Significant effort has been devoted to planning, resulting in a detailed
•
•
•
•
undulator construction schedule that is integrated with the BPM,
quadrupole and vacuum chamber construction and testing. The
undulator schedule and the magnet measurement schedule are mostly
integrated, and are consistent with completion of undulator systems in
July 2007.
A skeleton installation schedule exists; details are being added and
integration with the rest of the schedule is ongoing.
Schedule refinement is ongoing.
Costs were estimated by in-house experts with relevant experience and
were based on vendor quotes and previous experience. Cost scrubbing
will continue.
The greatest schedule risks come from:
- Design changes
- Delayed funding
42
Pioneering
Science and
Technology
Office of Science
U.S. Department
of Energy