Physics Requirements
Heinz-Dieter Nuhn, SLAC / LCLS
October 20, 2005
System Component Description
Tolerance Budget based on Genesis Simulations
Requirements and Procedures
Physics Requirements – October 20, 2005
1
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Linac Coherent Light Source
Undulator
Near Hall
Far Hall
Physics Requirements – October 20, 2005
2
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Physics Requirements – October 20, 2005
3
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Summary of Nominal Undulator Parameters
Undulator Type
Magnet Material
Wiggle Plane
Gap
Period Length
Effective On-Axis Field
Range of Effective Undulator Parameter K
Tolerance for K
Accumulated Segment Phase Error Tolerance
(at any point along segment)
planar hybrid
NdFeB
horizontal
6.8
30.0±0.05
1.249
3.500 - 3.493 (3.480)
± 0.015%
± 10
Segment Length
Number of Segments
Undulator Magnetic Length
3.40
33
112.2
m
Standard Break Lengths
Nominal Total Device Length
47.0 - 47.0 - 89.8
131.52
cm
m
Quadrupole Magnet Technology
Nominal Quadrupole Magnet Length
Integrated Quadrupole Gradient
EMQ
7
3.0
cm
T
Physics Requirements – October 20, 2005
4
Internal LCLS Undulator Alignment and Motion Review
mm
mm
T
degrees
m
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Undulator Segment Prototype
Physics Requirements – October 20, 2005
5
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Short Break Section Components
Beam Finder Wire
RF Cavity BPM
Undulator Segment
Quadrupole
Physics Requirements – October 20, 2005
6
Internal LCLS Undulator Alignment and Motion Review
Cherenkov Detector
Undulator Segment
Heinz-Dieter Nuhn, SLAC / LCLS
Courtesy of Dean Walters
Nuhn@slac.stanford.edu
Long Break Section Components
Beam Finder Wire
Diagnostics Tank
RF Cavity BPM
Undulator Segment
Quadrupole
Physics Requirements – October 20, 2005
7
Internal LCLS Undulator Alignment and Motion Review
Cherenkov Detector
Undulator Segment
Heinz-Dieter Nuhn, SLAC / LCLS
Courtesy of Dean Walters
Nuhn@slac.stanford.edu
Requirement Documents
Doc Type
Number
Title
GRD
1.1-001
Global Requirement Document
http://ssrl.slac.stanford.edu/lcls/prd/1.1-001-r1.pdf
PRD
1.1-002
LCLS Start-Up Test Plan
http://ssrl.slac.stanford.edu/lcls/prd/1.1-002-r0.pdf
PRD
1.1-003
Conventional Alignment System Requirements
http://ssrl.slac.stanford.edu/lcls/prd/1.1-003-r1.pdf
PRD
1.4-001
General Undulator System Requirements
http://ssrl.slac.stanford.edu/lcls/prd/1.4-001-r3.pdf
PRD
1.4-002
Magnetic Measurement Facility Requirements
http://ssrl.slac.stanford.edu/lcls/prd/1.4-002-r0.pdf
PRD
1.4-003
Undulator Beam Based Alignment System Requirements
http://ssrl.slac.stanford.edu/lcls/prd/1.4-003-r2.pdf
PRD
1.4-004
Undulator Beam Finder Wire
http://ssrl.slac.stanford.edu/lcls/prd/1.4-004-r0.pdf
ESD
1.4-104
Wire Position Monitor System Specifications
ESD
1.4-105
Hydrostatic Leveling System Specifications
http://ssrl.slac.stanford.edu/lcls/prd/1.4-105-r0.pdf
Heinz-Dieter Nuhn, SLAC / LCLS
Physics Requirements – October
20, 2005
8
Nuhn@slac.stanford.edu
Internal LCLS Undulator Alignment and Motion Review
LCLS Undulator Tolerance Budget Analysis
Based On Time Dependent SASE Simulations in 2 Phases
Simulation Code: Genesis 1.3
Simulate Individual Error Sources
Combine Results into Error Budget
Physics Requirements – October 20, 2005
9
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Parameters for Tolerance Study
The following 8 errors are considered:
Beta-Function Mismatch,
Launch Position Error,
Module Detuning,
Module Offset in x,
Module Offset in y,
Quadrupole Gradient Error,
Transverse Quadrupole Offset,
Break Length Error.
The ‘observed’ parameter is the average of the FEL power
at 90 m (around saturation) and 130 m (undulator exit)
Physics Requirements – October 20, 2005
10
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I - Individual Study
Time-dependent runs with increasing error source (uniform
distribution) and different error seeds. Gauss fit to obtain
rms-dependence.
2
Pi  P0 e

xi
2 i2
Pi  P0 e i
i  x 2
1
 2
2
Detailed Analysis Description
Physics Requirements – October 20, 2005
11
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 1b: Optics Mismatch
Simulation and fit results of Optics
Mismatch analysis. The larger
amplitude data occur at the 114-mpoint, the smaller amplitude data at the
80-m-point. 1
xi   
2
  0  2 0  0 
Transformation from negative
exponential to Gaussian:
  1  x2
m2  2 2
  m2 / 2
Optics Mismatch (Gauss Fit)
Physics Requirements – October 20, 2005
12
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
080 m
0.58
114 m
0.71
Average
0.64
z < 1.41
Unit
Heinz-Dieter
Nuhn,
SLAC / LCLS
Z. Huang
Simulations
Nuhn@slac.stanford.edu
Comparison of z vs. /0
1
    0  2 0   0 
2
+
-
1- value
Physics Requirements – October 20, 2005
13
Internal LCLS Undulator Alignment and Motion Review
Simplifies at waist location:
0  0
1   0 
   
2  0  
or, resolved for 

2

z

z
1
 
 0 
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 2: Transverse Beam Offset
Simulation and fit results of
Transverse Beam Offset (Launch
Error) analysis. The larger amplitude
data occur at the 130-m-point, the
smaller amplitude data at the 90-mpoint.
xi  Horiz. Launch Position
Physics Requirements – October 20, 2005
14
Internal LCLS Undulator Alignment and Motion Review
Transverse Beam Offset (Gauss Fit) /
2
Location
Fit rms
Unit
090 m
25.1
µm
130 m
21.1
µm
Average
23.1
µm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 3: Module Detuning
Simulation and fit results of Module
Detuning analysis. The larger
amplitude data occur at the 130-mpoint, the smaller amplitude data at the
90-m-point.
xi  K / K
Module Detuning (Gauss Fit)
Physics Requirements – October 20, 2005
15
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
Unit
090 m
0.042
%
130 m
0.060
%
Average
0.051
%
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 4: Horizontal Module Offset
Simulation and fit results of Horizontal
Module Offset analysis. The larger
amplitude data occur at the 130-mpoint, the smaller amplitude data at the
90-m-point.
Horizontal Model Offset (Gauss Fit)
Physics Requirements – October 20, 2005
16
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
Unit
090 m
0782
µm
130 m
1121
µm
Average
0952
µm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 5: Vertical Module Offset
Simulation and fit results of Vertical
Module Offset analysis. The larger
amplitude data occur at the 130-mpoint, the smaller amplitude data at the
90-m-point.
Vertical Model Offset (Gauss Fit)
Physics Requirements – October 20, 2005
17
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
Unit
090 m
268
µm
130 m
268
µm
Average
268
µm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 6: Quad Field Variation
Simulation and fit results of Quad
Field Variation analysis. The larger
amplitude data occur at the 130-mpoint, the smaller amplitude data at the
90-m-point.
Quad Field Variation (Gauss Fit)
Physics Requirements – October 20, 2005
18
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
Unit
090 m
8.7
%
130 m
8.8
%
Average
8.7
%
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 7: Transverse Quad Offset Error
Simulation and fit results of
Transverse Quad Offset Error analysis.
The larger amplitude data occur at the
130-m-point, the smaller amplitude
data at the 90-m-point.
Transverse Quad Offset Error (Gauss Fit)
Physics Requirements – October 20, 2005
19
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
Unit
090 m
4.1
µm
130 m
4.7
µm
Average
4.4
µm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step I – Error 8: Break Length Error
Simulation and fit results of Break
Length Error analysis. The larger
amplitude data occur at the 130-mpoint, the smaller amplitude data at the
90-m-point.
Break Length Error (Gauss Fit)
Physics Requirements – October 20, 2005
20
Internal LCLS Undulator Alignment and Motion Review
Location
Fit rms
Unit
090 m
13.9
mm
130 m
20.3
mm
Average
17.1
mm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step II - Tolerance Budget
Assuming that each error is independent on each other (validity of this
assumption is limited)
tolerance
Each should yield the same degradation
fitted rms
xi2
1
1
n
 2
 fi 2
  fi 2
 f2
P
  e 2 i   e 2  e 2
e 2
P0
fi=xi/i
unit weights
n=8
Tolerance is defined for a given power degradation
2  P0 
f 
ln 
n P
Physics Requirements – October 20, 2005
21
Internal LCLS Undulator Alignment and Motion Review

1 - P/P0
f
20 %
0.236
25 %
0.268
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step III - Correlated Error Sources
For the simplest approach, the tolerance budget assumes
uncorrelated errors of 8 different sources.
Some tolerances (e.g. the break length error) are very
relaxed and can be reduced to relax other tolerances, i.e.
use individual tolerances.
1
  fi 2
P
e 2
P0
Next step is to combine all error sources in the simulation.
Include BBA and other correction scheme in the runs
Physics Requirements – October 20, 2005
22
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Step II - Tolerance Budget (cont’)
Error Source
<  i>
<  i> f
<  i > fi
fi
f=0.268
(25% red.)
(24.2% red.)
Units
z < 1.1
Hor/Ver Optics Mismatch (z-1)0.5
0.64
0.19
0.453
0.32
Hor/Ver Transverse Beam Offset
23
5.7
0.177
3.7
µm
0.051
0.016
0.402
0.024
%
Module Offset in x
952
301
0.125
140
µm
Module Offset in y
268
72
0.298
80
µm
Quadrupole Gradient Error
8.7
2.3
0.028
0.25
%
Transverse Quadrupole Offset
4.4
1.3
0.215
1.0
µm
Break Length Error
17.1
5.4
0.048
1.0
mm
Module Detuning K/K
Physics Requirements – October 20, 2005
23
Internal LCLS Undulator Alignment and Motion Review
Can be mitigated
through
steering.
Heinz-Dieter
Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Model Detuning Sub-Budget
K  K MMF   K T   K x
 K 
2
 K

 
 pi 
i  pi

Typical Value
rms dev. pi
3.5
0.0003
K
-0.0019 °C-1
0.0001 °C-1
T
0 °C
0.32 °C
K
0.0023 mm-1
0.00004 mm-1
x
1.5 mm
0.05 mm
Parameter pi
KMMF
K 
2
Note
±0.015 % uniform
Thermal Coefficient
±0.56 °C uniform without compensation
Canting Coefficient
Horizontal Positioning
 KMMF    T K    KT    x K     Kx 
2
2
2
2
2
 K / K  0.020%
Physics Requirements – October 20, 2005
24
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Undulator Pole Canting
• 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
Physics Requirements – October 20, 2005
25
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Using Undulator Roll-Away and K Adjustment Function
Standard Undulator Segment
Axis (SUSA) as defined during
tuning process.
SUSA
SUSA defines Girder Axis (GA)
in neutral Segment position.
SUSA moves with Segment, GA
does not.
GA
Neutral; K=3.5000; x=+0.0 mm
PowerTp; K=3.4804; x=+8.5 mm
Both axes refer to undulator
fiducials.
SUSA
GA is the basic reference line
for the relative alignment of
Beamline components.
GA
SpontTp; K=3.4929; x=+3.0 mm
Physics Requirements – October 20, 2005
26
Internal LCLS Undulator Alignment and Motion Review
RollAway; K=0.0000; x=+100 mm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Segment K Adjustments for Overall Tapering
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
Physics Requirements – October 20, 2005
27
Internal LCLS Undulator Alignment and Motion 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 0.6% total)
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Measurement of SASE Gain Using Rollout
Undulator Segments can be removed
by remote control from the end of the
undulator. They will not effect
radiation produced by earlier
segments.
Physics Requirements – October 20, 2005
28
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Root Requirements for FEL Gain
Effective K Value Tolerance
The effective K value for each undulator along the electron path shall not deviate by more that
±0.024 % from its design value.
Undulator Tuning
Temperature Control
Undulator Segment Alignment
Pole Canting with Horizontal Position Control
Phase Tolerance
The average longitudinal electron bunch position shall not deviate by more that ±10 degrees of
x-ray phase (±4 pm) from its design value over the distance of one gain length.
Trajectory Control (Tight Control and Stability of Quadrupole Centers)
Overlap Tolerance
The rms deviation between the transverse center of the electron beam and the center of the
radiation field shall be less than 10% of the rms of the electron beam distribution.
Control and Stabilization of Launch Coordinates
Trajectory Control
Physics Requirements – October 20, 2005
29
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Implication from Phase Tolerance
Tight Phase Tolerance Requires
Extremely straight trajectory
(~3 µm rms over 10 m)
Precise positioning of quadrupoles
(±2 µm wrt. straight line)
Use of Beam Based Alignment (BBA) methods
Basic Conventional Alignment and Motion Strategy
Alignment of components as needed to start BBA
Monitoring of component motion during and between BBA
procedures.
The latter is to mitigate effects of ground motion and to lengthen
time needed between BBA procedures.
Physics Requirements – October 20, 2005
30
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Main Alignment Monitoring Elements
Hydrostatic Leveling System Device (HLS)
Monitored Degrees of Freedom: y, pitch, and roll
Wire Position Monitoring Device (WPM)
Monitored Degrees of Freedom: x, yaw, and roll
Temperature Sensors
BPMs (Transverse Locations Tracked by HLS and WPM)
Physics Requirements – October 20, 2005
31
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Main Alignment Control Elements
Relative alignment between undulator segments and break section
components will be achieved and maintained through common-girder
mounting
Overall alignment are (remotely) controlled through Girder movement
based on cam-shaft technology
During initial alignment
For quadrupole position control, i.e. beam steering during BBA
For compensation of ground motion effects etc.
Quadrupoles are used as beam steering elements
Main steering function comes from off-center dipole fields. Change is done
through cam-based girder motion, which will align all girder components to
the beam.
Dipole trim-windings are used for fine adjustments
Physics Requirements – October 20, 2005
32
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Girder Components Summary
Main girder components include
Beam Finder Wire
Undulator strongback arrangement mounted on horizontal slides
Vacuum chamber support
BPM
Quadrupole
WPM sensors
HLS sensors
(diagnostics components)
The undulator strongback arrangement (Segment) is mountable on and
removable from the girder with the vacuum chamber in place and
without compromising the alignment of the vacuum chamber
Segments will be taken off the girder for magnetic measurements
Segments need to be mechanically interchangeable
The complete Girder assembly will be aligned on the Coordinate
Measurement Machine (CMM).
Physics Requirements – October 20, 2005
33
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Undulator Motion Summary
Remotely Controlled Motion:
Undulator: x
Provides control of undulator field on beam axis.
Horizontal slide stages move undulator strongback independent of
Girder and vacuum chamber.
Girder: x, y, pitch, yaw, roll
Enables alignment of all beamline components to beam axis.
transverse motion of meeting girder ends can be coupled
roll motion capability is to be used to keep roll constant
Additional Manual Adjustments:
Rough CAM position adjustability relative to fixed support.
Quadrupole, BFW, Vacuum Chamber, and BPM position
adjustability to Girder.
Physics Requirements – October 20, 2005
34
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Segment Alignment using Beam Finder Wire
Downstream quad and upstream monitor fiducialized to undulator ends
BBA facilitates alignment of downstream cradle end and straightens electron beam
Use Beam Finder Wire reading to determine and correct “loose” end offset
Monitoring System WPM and HLS provide real-time girder position information
Info can be used as feed-back for mover system to maintain initial alignment
Undulator Strongback
Before any BBA performed
Quad
After BBA: Quad, BPM and one end of undulator aligned
Girder
Beam Finder Wire
RF BPM
After centering of Upstream Monitor: Both ends of undulator aligned
Beam
Physics Requirements – October 20, 2005
35
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Undulator – to – BFW Alignment
Tolerance Budget
Vertical
[µm]
Horizontal
[µm]
20
10
20
30
20
10
20
30
20
15
20
20
40
20
30
30
20
50
X-Wire Positioning Repeatability
-
80
Y-Wire Positioning Repeatability
30
-
CAM Positioning Repeatability
4
4
Undulator Segment Roll-Away Repeatability
10
10
Alignment BFW to Undulator
55
100
Grand Total
80
140
BFW Fiducials
BFW Wire to Reference Stop
Reference Stop Definition
Reference Stop Fiducial
Undulator Fiducials
Hall Probe Resolution/Positioning
Needle Hall Probe Resolution
Needle Center to Fiducial
Fixture Fiducial to Undulator Fiducial
Individual contributions are added in quadrature
Physics Requirements – October 20, 2005
36
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Undulator – to – Quad Alignment
Tolerance Budget
Vertical
[µm]
Horizontal
[µm]
10
20
10
25
10
20
10
25
20
20
20
15
20
20
40
20
30
30
20
50
Undulator Segment Roll-Away Repeatability
10
10
Alignment Quadrupole to Undulator
60
125
Grand Total
80
140
Quadrupole Fiducials
Pulsed Wire Center Definition
Wire to Wire Finder (WF) Fiducial
WF Fiducial to Quadrupole Fiducial
Quadrupole BBA Offset
Undulator Fiducials
Hall Probe Resolution/Positioning
Needle Hall Probe Resolution
Needle Center to Fiducial
Fixture Fiducial to Undulator Fiducial
Individual contributions are added in quadrature
Physics Requirements – October 20, 2005
37
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Main Alignment Procedures Overview
Undulator Segment Tuning and Fiducialization (Establishes SUSA)
Quadrupole Fiducialization
Beam Finder Wire Fiducialization
Complete Component Installation and Alignment on Girder
Earth Field Compensation Measurement in Tunnel
Girder Installation and Pre-Alignment in Tunnel
Complete Installation and Checkouts of WPM and HLS
Undulator Segment Installation on Girder
Girder Alignment with Portable WPM / HLS
Continuous Component Position Monitoring through WPM and HLS
Beam-Based Alignment
Periodic Rebaselining to Correct for Ground Motion etc.
Physics Requirements – October 20, 2005
38
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Conventional Alignment Tolerance Overview
Tolerances for Component Alignment on Girder
Value
Horizontal rms alignment of quadrupole and BPM to Segment (rms)
Vertical rms alignment of quadrupole and BPM to Segment (rms)
Horizontal rms alignment of BFW to Segment (rms)
Vertical rms alignment of BFW to Segment (rms)
Tolerances for Girder Alignment in Tunnel
Unit
125
µm
60
µm
100
µm
55
µm
Value
Unit
Initial rms uncorrelated x/y quadrupole alignment tolerance wrt straight line
100
µm
Initial rms correlated x/y quadrupole alignment tolerance wrt straight line
300
µm
Longitudinal Girder alignment tolerance
±1
mm
Undulator Segment yaw tolerance (rms)
240
µrad
Undulator Segment pitch tolerance (rms)
80
µrad
1000
µrad
Value
Unit
Undulator Segment roll tolerance (rms)
Component Monitoring and Control Tolerance
Horizontal / Vertical Quadrupole and BPM Positions
Physics Requirements – October 20, 2005
39
Internal LCLS Undulator Alignment and Motion Review
±2
µm
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
Conclusions
The X-ray-FEL puts very tight tolerances on magnetic field quality,
electron beam straightness, and Segment alignment.
Alignment tolerances from electron beam straightness requirements can
not be achieved with conventional alignment but require Beam Based
Alignment (BBA) Procedure.
Main task of conventional alignment and motion systems are
SUSA determination and fiducialization
Alignment of undulator segments (relative to adjacent quadrupole centers)
Conventional alignment as prerequisite for BBA
Provision of remotely controlled motion capability to support, alignment
processes
Monitoring of component positions in the presence of ground motion etc.
Requirements and Specifications are available from the LCLS WEB site.
The main Physics Requirements Document (PRD) outlining the
requirements for the undulator system is PRD1.4-001.
Physics Requirements – October 20, 2005
40
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu
End of Presentation
Physics Requirements – October 20, 2005
41
Internal LCLS Undulator Alignment and Motion Review
Heinz-Dieter Nuhn, SLAC / LCLS
Nuhn@slac.stanford.edu