Transcript Introduction to the LCLS Undulators

Introduction to the LCLS Undulators
Heinz-Dieter Nuhn, SLAC / LCLS
October 14, 2004
Undulator Overview
Requirement Documents
Undulator Fields and Tapering
Cradle Components and Motion
MMF Physics Requirements
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Linac Coherent Light Source
Undulator
Near Hall
Far Hall
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Undulator Segment Prototype
LCLS Undulators October 14, 2004
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Heinz-Dieter Nuhn, SLAC / SSRL
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Undulator Requirement Documents
Index URL:
http://www-ssrl.slac.stanford.edu/lcls/requirements.html
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Summary of Nominal Undulator Parameters
Undulator Type
Magnet Material
Wiggle Plane
Gap
Period Length
Effective On-Axis Field
Standard Effective K
Range of Effective Undulator Parameter K
Accumulated Segment Phase Error Tolerance
(at any point along segment)
planar hybrid
NdFeB
horizontal
6.8
30.0 ± 0.05
1.249
3.49290 ± 0.015%
3.5000 - 3.4929 (3.4804)
10
Module Length
Number of Modules
Undulator Magnet Length
3.40
33
112.2
m
Standard Break Lengths
Nominal Total Device Length
48.2 - 48.2 - 94.9
130.954
cm
m
Quadrupole Magnet Technology
Nominal Quadrupole Magnet Length
Integrated Quadrupole Gradient
EMQ
7
3.0
cm
T
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mm
mm
T
degrees
m
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Micro Tapering V: K values
The following list contains the nominal K values
for the 33 undulator segments for the 6.8 mm gap
height:
Undulator Segment
Keff
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
3.5000
3.4998
3.4996
3.4993
3.4991
3.4989
3.4987
3.4984
3.4982
3.4980
3.4978
3.4976
3.4973
3.4971
3.4969
3.4967
3.4964
3.4962
3.4960
3.4958
3.4955
3.4953
3.4951
3.4949
3.4947
3.4944
3.4942
3.4940
3.4938
3.4935
3.4933
3.4931
3.4929
LCLS Undulators October 14, 2004
MMF Review
To compensate energy loss
from spontaneous radiation
This amount of tapering requires only a negligible
adjustment for break lengths.
After achieving goal performance, tapering beyond
saturation point is desirable. (up to 0.56% total)
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Undulator Pole Canting
Suggested by J. Pflueger, DESY
• Canting comes from wedged
spacers
• 4.5 mrad cant angle
• Gap can be adjusted by lateral
displacement of wedges
• 1 mm shift means 4.5 microns in
gap, or 8.2 Gauss
• Beff adjusted to desired value
Source: Liz Moog
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Canting the poles helps in many ways
Facilitates final setting of Beff
Remote control of position allows run-time
adjustment
Allows compensating for temperature effect on
field strength: ±1.0°C temperature error would
require ±1.2 mm lateral shift of undulator
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SourceSLAC
Liz Moog/ SSRL
Heinz-Dieter Nuhn,
[email protected]
Effective B field vs. x
See I. Vasserman’s Talk for
Prototype Measurements
Measured slope of 6.6 Gauss/mm agrees with calculations
(~ 5.7 Gauss/mm for 3 mrad cant)
Field variation allowance between segments is DB/B = 1.5x10-4, or
DB = 2 Gauss, which translates to Dx = 0.3 mm ( or 1 micron in gap)
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SourceSLAC
Liz Moog/ SSRL
Heinz-Dieter Nuhn,
[email protected]
Using Undulator Roll-Away and K Adjustment Function
Neutral; K=3.4965; Dx=+0.0 mm
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First; K=3.5000; Dx=-1.5 mm
PowerTp; K=3.4804; Dx=+7.0 mm
Last; K=3.4929; Dx=+1.5 mm
RollAway; K=0.0000; Dx=+100 mm
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Cradle Components
Cradle Components include
Undulator strongback arrangement mounted on horizontal slides
Vacuum chamber support
BPM
Quadrupole
WPM sensors
HLS sensors
(diagnostics chamber)
The undulator strongback arrangement (segment) is mountable on
and removable from the cradle with the vacuum chamber in place and
without compromising the alignment of the vacuum chamber.
Undulator strongback can be taken off the cradle for magnetic
measurements
Complete cradle assembly will be aligned on Coordinate
Measurement Machine (CMM).
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Motions of the Cradle and of Cradle Components
Remotely Controlled
Motion:
Cradle: x, y, roll
x, y motion of cradle
ends are coupled
roll motion capability is
to be used to keep roll
constant
Undulator: x
Horizontal slide stages
move undulator
strongback
independent of cradle
and vacuum chamber
Manual Adjustment:
Cradle Movers to fixed
support girder (AMP)
Quadrupole and BPM
position to cradle.
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
MMF Physics Requirements
Earth Magnetic Field Compensation
Establish environmental magnet field in MMF to be equal to the environmental field
at target location in undulator hall to better than 0.01 T. See J. Welch’s and I Vasserman’s
MMF Temperature
talks for details
Average ambient MMF temperature needs be 20.0 ± 0.1 oC to match the ambient
undulator hall temperature of 20.0 ± 0.2 oC.
Magnetic Undulator Shimming to
Reduce phase error below 10 degrees at 0.15 nm.
Reduce 1st Field Integral below ±40×10-6 Tm
Reduce 2nd Field Integral below ±50×10-6 Tm2
Definition of Standard Undulator Axis (SUSA) so that
SUSA is Parallel to Undulator Center Line
Effective K along SUSA is 3.4965 ± 0.0005
Alignment of Quadrupole on Cradle with respect to CA*.
Tolerance: 40 mm (rms).
Routine Operational Checking of Undulator Segments
*Cradle Axis (CA) is identical to
SUSA when undulator segment is
in neutral horizontal position
Remove 3 segments / month from undulator hall and replace with spares
Characterize magnetic field of removed segments and prepare for re-installation.
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
Conclusions
Requirements and Specifications are available from the LCLS WEB site.
http://ssrl.slac.stanford.edu/lcls/internals/requirements.html
The main Physics Requirements Document (PRD) outlining the
requirements for the undulator system is PRD1.4-001. The MMF
specifications are found in PRD1.4-002.
Main Physics Task to be done at the MMF are
Undulator magnetic field tuning to specifications under same surrounding
magnetic field and temperature conditions as at target location in undulator
hall.
Quadrupole and BPM alignment on cradle with respect to undulator
strongback
Characterization of undulators that have been used in operation
All undulator segments will be tuned identically.
Micro-tapering implies that every undulator core be at a slightly different K
value, which will be accomplished by horizontal positioning.
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]
End of Presentation
LCLS Undulators October 14, 2004
MMF Review
Heinz-Dieter Nuhn, SLAC / SSRL
[email protected]