Transcript Undulator Physics Issues

Undulator Physics Issues
Heinz-Dieter Nuhn, SLAC / LCLS
October 30, 2007
Vacuum Chamber Update
Tuning Status
First Article Quadrupole Measurements
Beam Loss Monitors
October 30, 2007
Undulator Physics Issues
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Vacuum Chamber Update
At the last FAC meeting the stainless steel chamber had been cut to produce
samples for permeability and roughness measurements of the coated surface.
The measurements were completed after the meeting with negative results:
The surface roughness of the finished chamber was much larger (2.5 times the
tolerance) than that of the untreated stainless steel samples.
The presence of the chamber significantly changed the on-axis magnetic field of the
undulator.
A particularly large modification of the effect of the phase shims was observed.
[See presentation by Z. Wolf]
The effects on the magnetic field clearly made the stainless steel chamber
unusable.
At the DOE review it was decided to slightly reduce roughness requirements
and to examine three alternatives:
Extruded Aluminum [Argonne]
Aluminum Clam Shell [SLAC]
Plain Copper Pipe [Argonne] FALL-BACK SOLUTION
In the meantime, the Extruded Aluminum chamber development proceeded to
produce a full vacuum chamber meeting all tolerances.
October 30, 2007
Undulator Physics Issues
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Tuning Results
The procedures for tuning and measuring the LCLS undulator magnets are described
in LCLS-TN-06-17
“LCLS Undulator Test Plan”
The document identifies three distinct phases:
• Rough Tuning
• Fine Tuning
• Tuning Results (Final Measurements)
During Rough Tuning, a target position (Slot number) is assigned to the undulator
based on its strength and the gap height is adjusted according to the Slot number.
During Fine Tuning, the tuning axis is determined and the magnetic fields are corrected
along that axis. In addition, the field integrals in the roll-out location are measured and
corrected, as necessary.
The Final Measurement phase begins after the tuning process is completed. Its
purpose is to document the tuning results and to provide data necessary for
understanding the behavior of the undulator during commissioning and operation.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Tuning Requirements
1. At Tuning Axis
Parameter
Target Value
Tolerance
Comment
Keff
See Table
0.015 %
Effective Undulator parameter
I1x
0 µTm
 40 µTm
First Horizontal Field Integral
I2x
0 µTm2
 50 µTm2
Second Horizontal Field Integral
I1y
0 µTm
 40 µTm
First Vertical Field Integral
I2y
0 µTm2
 50 µTm2
Second Vertical Field Integral
113 × 360º
 10º
Total Undulator Segment phase slippage
Avg core phase shake*)
0º
 10º
Average phase deviation along z for core periods
RMS core phase shake*)
0º
 10º
RMS phase deviation along z for core periods
Total Phase (over 3.656 m)*)
*) For radiation wavelength of 1.5 Å
2. At Roll-Out Position (Deviation from Background Fields)
Parameter
Target Value
Tolerance
Comment
I1x
0 µTm
 40 µTm
First Horizontal Field Integral
I2x
0 µTm2
 50 µTm2
Second Horizontal Field Integral
I1y
0 µTm
 40 µTm
First Vertical Field Integral
I2y
0 µTm2
 50 µTm2
Second Vertical Field Integral
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
ref
Tuning Status as of 10/26/2007
SN01: @ANL
SN02: Tuning and Fiducialization Complete. [01]
SN03: Tuning and Fiducialization Complete. [25]
SN04:
SN05:
SN06: On hold …
SN07: Tuning and Fiducialization Complete. [19]
SN08:
SN09:
SN10:
SN11: Tuning and Fiducialization Complete. [03]
SN12: Tuning and Fiducialization Complete. [21]
SN13: Tuning and Fiducialization Complete. [04]
SN14: Tuning and Fiducialization Complete. [09]
SN15: Tuning and Fiducialization Complete. [32]
SN16:
SN17: Tuning and Fiducialization Complete. [02]
SN18:
SN19: Tuning and Fiducialization Complete. [05]
SN20: Tuning and Fiducialization Complete. [33]
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SN21:
SN22:
SN23: On hold …
SN24: Tuning and Fiducialization Complete. [13]
SN25: Tuning and Fiducialization Complete. [10]
SN26:
SN27:
SN28:
SN29:
SN30:
SN31:
SN32: Tuning and Fiducialization Complete. [30]
SN33:
SN34:
SN35: Rough Tuning …
SN36: On hold …
SN37: Tuning and Fiducialization Complete. [18]
SN38:
SN39: Fine Tuning …
SN40:
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Keff well within Tolerance
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Phase Difference well within Tolerance
Calculated for E = 13.6 GeV
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
On-Axis Field Integrals within Tolerance
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
(Earth-Field-Corrected) Roll-Out Field Integrals Too Large
Requires Significant Steering Corrections
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
First Article Quadrupole Measurements
Two first articles of the undulator
quadrupoles have been received at
Argonne.
After initial checks on both magnets
at Argonne one was sent to SLAC,
the other was kept at Argonne for
more detailed magnetic
measurements.
The SLAC measurements have been carried out by Scott
Anderson from the Metrology group.
Some of those results are presented on the following
slides.
Photo Mark Jaski
October 30, 2007
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Undulator Quad Tasks
Vibrating Wire cam mover fixture checked out with Undulator Quad. 
Fiducialize on CMM. 
Measure thermal constants for Quad  and Trim  coils.
Measure Integrated Gradient of Quad and H-Trim with Stretched Wire
System. 
Calibrate Radial Coil using Stretched Wire data. 
Measure Integrated Gradient and Harmonics at specified currents
using Radial Coil. 
Measure magnetic center shifts for Quad  & Trim currents and
magnet splitting using Radial Coil. 
Fiducialize the quad to the Magnetic Center using Vibrating Wire.
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Courtesy ofNuhn,
ScottSLAC
Anderson
Heinz-Dieter
/ LCLS
[email protected]
Quadrupole Temperature Rise Test at 4 A
Data at 4 A
Mirror plates on.
Ambient = 21.5 ˚C
5 Hours
∆T Upper Coil = 6.2 ˚C
∆T Lower Coil = 5.6 ˚C
∆T Outer Steel = 3.4 ˚C
∆T Base = 1 ˚C
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Heinz-Dieter Nuhn, SLAC / LCLS
Courtesy of Scott Anderson
[email protected]
Quadrupole Temperature Rise Test at 6 A
Data at 6 A
Mirror plates on.
Ambient = 21.5 ˚C
14 hours
∆T Upper Coil = 14 ˚C
∆T Lower Coil = 13 ˚C
∆T Outer Steel = 8 ˚C
∆T Base = 3 ˚C
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Heinz-Dieter Nuhn, SLAC / LCLS
Courtesy of Scott Anderson
[email protected]
Quadrupole Temperature Rise Profile Estimates
Main Operating Points
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Quadrupole Heating Concerns
The quadrupole steel temperature is elevated by about 78 ˚C at regular operating current of 4.5 A.
Indirect heating of adjacent component are being
investigated:
Quadrupole Stand
Temperature increase is less than 2 ˚C. Stand expansion will raise
quadrupole position. This can be taken into account during alignment.
BPM
Temperature increase of less than 0.5 ˚C has been measured. While a
temperature change of that amplitude is a concern, a constant
temperature shift is acceptable.
Undulator
Temperature change is still under investigation.
Possibility of temperature gradient along undulator is a concern.
Undulator heating from sources other than the quadrupole (undergirder racks) is being reduced through air flow guiding.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Stretched Wire Measurements
Quad
GL = 3.9671 ± 0.0028 T at 6.00521 ± 0.00002 A
GL/I = 0.6606 ± 0.0005 T/A
H-trim
BL/I = 677.9 ± 4.7 µTm/A
Good Agreement with
requested value of 4 T.
Photo Scott Anderson
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Radial Coil
Calibrated with Stretched wire.
Measures Integrated Gradient and Harmonics.
Measures relative changes in magnetic center to less than a micron.
Photo Scott Anderson
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Quadruple Harmonics Analysis
Harmonic amplitudes negligible
Slight Coil Misalignment
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Center Shift vs. Quadrupole Current
Y Center Shift vs. Current
X Center Shift vs. Current
October 30, 2007
Undulator Physics Issues
Main Operating Areas
±0.9 A × ±2.5 µm
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Center Shift vs. Corrector Current
Quadrupole Corrector Test
Procedure:
1)With Corrector Currents
set to 0 A, demagnetize
quadrupole with main coil.
Large Size Corrector Current Loop
Medium Size Corrector Current Loop
Rotation due to coil misalignment
Hysteresis effects much smaller than expected
2)Set main coils to
operating value of 4.5 A.
3)Set correctors to initial
values:
0.0 A / 0.0 A for lrge loop
0.5 A/ 0.5 A for med loop
4)Move corrector currents
to corners of square and
back to initial value and
measure magnetic center
at each stop.
Correctors perform very
well.
They would be very useful
during commissioning and
operation.
But, presently no budget for
power supplies!
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Additional Quadrupole Test
Quadrupole Split Test
X Center shift = 1.27 ± 0.75 µm
Y Center shift = -1.43 ± 0.27 µm
Effect of Mirror Plates on Integrated Gradient
Mirror Plates Installed: GL = 3.9671 ± 0.0028 T
Mirror Plates Removed: GL = 3.9857 ± 0.0028 T
Ratio Remove/Installed: 1.0047 ± 0.0007
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Beam Loss Monitors (BLMs)
Radiation protection of the permanent magnet
blocks is very important.
Funds are limited and efforts need to be focused
to minimize costs.
A Physics Requirement Document, PRD 1.4-005
has been completed, defining the minimum
requirements for the Beam Loss Monitors.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Beam Loss Monitor Area Coverage
Main purpose of BLM is the
protection of undulator magnet
blocks.
Less damage expected when
segments are rolled-out.
Radiation is expected to peak in
beam direction.
One BLM will be positioned in front
of each segment.
Its active area will cover the full
horizontal width of the magnet
blocks
The BLM will be moved with the
segment to keep the active BLM
area at a fixed relation to the
magnet blocks.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
BLM Purpose
The BLM will be used for two purposes
A: Inhibit bunches following an “above-threshold” radiation event.
B: Keep track of the accumulated exposure of the magnets in each
undulator.
Purpose A is of highest priority. It will be integrated into the
Machine Protection System (MPS) and requires only
limited dynamic range from the detectors.
Purpose B is desirable for understanding long-term magnet
damage in combination with the undulator exchange
program but requires a large dynamic range for the
radiation detectors (order 106) and much more
sophisticated diagnostics hard and software.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Additional Loss Monitors
Other Radiation Monitoring Devices
Dosimeters
Located at each undulator. Routinely replaced and evaluated.
Segmented Long Ion Chambers
Investigated
(Quartz)-Fibers
Investigated
Non-Radiative Loss Detectors
Pair of Charge Monitors (Toroids)
One upstream and one downstream of the undulator line
Used in comparator arrangement to detect losses of a few percent
Electron Beam Position Monitors (BPMs)
Continuously calculate trajectory and detect out-of-range situations
Quadrupole Positions and Corrector Power Supply Readbacks
Use deviation from setpoints
Estimate accumulated kicks to backup calculations based on BPMs.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Summary
Finally got a working design for the undulator
vacuum chamber.
Tuning of the first fifteen undulators complete.
Results are very encouraging.
A first article quadrupole has been tested and
found to meet expected performance.
The Beam Loss Monitor PRD has been
completed. Monitor design is under way.
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
End of Presentation
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Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]