1 Heinz-Dieter [email protected]
1Undulator CommissioningAugust 2009 FEL2009
Undulator Commissioning, Alignment and PerformanceHeinz-Dieter Nuhn – LCLS Undulator Group Leader
August 27, 2009
2 Heinz-Dieter [email protected]
2Undulator CommissioningAugust 2009 FEL2009
All 33 Undulator Segments Operational
3 Heinz-Dieter [email protected]
3Undulator CommissioningAugust 2009 FEL2009
Girder Components
Quadrupole and horz/vert Correctors
BFWUndulator Segment
Girder
Segment Slider
Girder Mover (cam)
RF Cavity BPM
HLS Sensor
Part of WPM Support
4 Heinz-Dieter [email protected]
4Undulator CommissioningAugust 2009 FEL2009
Undulator Beam Operation Highlights
December 13, 2008 First electron beam through undulator vacuum chamber without undulator segments.
No extra steering corrections necessary to get 100% transmission to main dump.
Pre-beam girder alignment was sufficient.
April 10, 2009 First electron beam through undulator segments.
Detected FEL beam after 105 minutes, CCD saturation 20 minutes later.
December 13, 2008 First electron beam through undulator vacuum chamber without undulator segments.
No extra steering corrections necessary to get 100% transmission to main dump.
Pre-beam girder alignment was sufficient.
April 10, 2009 First electron beam through undulator segments.
Detected FEL beam after 105 minutes, CCD saturation 20 minutes later.
5 Heinz-Dieter [email protected]
5Undulator CommissioningAugust 2009 FEL2009
Preparation for First Electron Beam
Extensive pre-beam checkout procedure
Precise girder alignment mapping (error ellipse about 50 µm)
Quadrupole position adjustment to remove residual deviations from straight line as reported by last alignment mapping data.
to add offsets to compensate for the environmental fields (earth magnetic field etc.) as measured with field probe (five points per girder).
Extensive pre-beam checkout procedure
Precise girder alignment mapping (error ellipse about 50 µm)
Quadrupole position adjustment to remove residual deviations from straight line as reported by last alignment mapping data.
to add offsets to compensate for the environmental fields (earth magnetic field etc.) as measured with field probe (five points per girder).
6 Heinz-Dieter [email protected]
6Undulator CommissioningAugust 2009 FEL2009
Mount and precision-align Undulator, Quad, BPM and BFW on girder
Align girders using conventional alignment to bring quadrupole centers onto straight line to 50 μm rms.
Beam straightness requirement through undulator: 2 μm rms per field gain length (about 7 m)
=> Use Beam Based Alignment (BBA) with set of different energies for final quadrupole alignment
Use BFW scans for upstream alignment.
Mount and precision-align Undulator, Quad, BPM and BFW on girder
Align girders using conventional alignment to bring quadrupole centers onto straight line to 50 μm rms.
Beam straightness requirement through undulator: 2 μm rms per field gain length (about 7 m)
=> Use Beam Based Alignment (BBA) with set of different energies for final quadrupole alignment
Use BFW scans for upstream alignment.
Undulator Line Alignment Overview
Beam
Undulator SegmentQuad/Corr
RFBPMRes < 1 μm
Conventional Girder Alignment Grossly out of scale for clarity
BFW
After BBA: all Quads aligned Wire inserted(One at a time)After BFW scan/alignWires extracted Ready for FEL
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7Undulator CommissioningAugust 2009 FEL2009
Beam Finder Wire
Electron ScatteringXray Scattering
8 Heinz-Dieter [email protected]
8Undulator CommissioningAugust 2009 FEL2009
Beam Based Alignment Principle
BPM offsets unknownMagnetic fields (earth, quad kicks, etc.) unknownTask: Correct field integrals using quad offsets or correctors for dispersion free trajectory at BPM positionsTrajectory between BPMs remains unknownMeasure trajectory at different energies to extrapolate to straight line at infinite energyKeep undulator quadrupole fields fixedBPM position is BPM offset at infinite energy
BPM offsets unknownMagnetic fields (earth, quad kicks, etc.) unknownTask: Correct field integrals using quad offsets or correctors for dispersion free trajectory at BPM positionsTrajectory between BPMs remains unknownMeasure trajectory at different energies to extrapolate to straight line at infinite energyKeep undulator quadrupole fields fixedBPM position is BPM offset at infinite energy
The following pages Illustrate the BBA Concept as implementedby Henrik Loos for the LCLS
9 Heinz-Dieter [email protected]
9Undulator CommissioningAugust 2009 FEL2009
Launch Parameters LE1, … , LE4 (Position & Angle; Energy dependent)
BBA Measurement Schematic
1 33j 1 37i
Δq1 Δq3Δq2
Δb1 Δb3Δb2
Δy1 Δy3Δy2Δy0 Δy4
Δb4Δb0
E1
E2
BPM Readings
LE1
E1 < E2
y = M xSolve Equations
LE2
Measure (y)
Obtain Results (x)
Positionsnot observable
BPM Reading
1 37j (each for h, v, and E)@ 4 Energies yj
Quad Offsets Δqj (each for h and v)BPM Offsets Δbi (each for h and v)
10 Heinz-Dieter [email protected]
10Undulator CommissioningAugust 2009 FEL2009
BBA M Matrix
=
Y M X
YH
YV
XH
XV
MH
MV
0
0
=
×
×
YH 150 × 1
XH 78 × 1
Y 300 × 1
X 156 × 1
M 300 × 156
11 Heinz-Dieter [email protected]
11Undulator CommissioningAugust 2009 FEL2009
BBA Horizontal M Matrix
XL2 × 1
ML37 × 2
C11 × 33
C21 × 33
=
YH MH XH
YHE1
XQ,H
=
XB,H
YHE2
YHE3
YHE4
XLHE1
MQHE1
MQHE2
MQHE3
MQHE4
MB
MB
MB
MB
MLHE1
MLHE2
MLHE3
MLHE4
XLHE2
XLHE3
XLHE4
×
×
Dimensions
MB37 × 37
MQ37 × 33
YH150 × 1
XH78 × 1
MH150 × 78C2C1
12 Heinz-Dieter [email protected]
12Undulator CommissioningAugust 2009 FEL2009
BBA Horizontal M Sub-Matrices and Vectors
1 0
0 1BM
LH h hX L L
37 × 37
1 4
1 5 2 5
1 37 2 37 3 37 33 37
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0
0 0QQ
Q Q
Q Q Q Q
mM
m m
m m m m
37 × 33
0 1 0 111 12
0 36 0 3611 12
L
R R
M
R R
37 × 2
, ,
11 11i end j i beg jQ BPM Q BPMi j
Qm R R
, ji endBPMQz zif
0therwise
1 1 1C 1 × 33
1 × 33
LHX 1 × 2
2 331C z z QQ : horizontal launch position;hL: horizontal launch angle;hL
0i jQm
LM QM
2C
BM
1C
BPM Offset Matrix
Launch Position Vector
Launch Trajectory Matrix
Constraint Vector <y>=0
Constraint Vector
Quad Mover Matrix
13 Heinz-Dieter [email protected]
13Undulator CommissioningAugust 2009 FEL2009
BBA Implementation
Setup accelerator for one energyCalculate response matrix for this energyMeasure N trajectories at this energy and averageRepeat for all energiesGenerate M-matrix with energy dependent elements and selected constraintsAdd constraint equations for quad or BPM offsets
0 = Σi Δqi and 0=Σi zi Δqi for linear quad offset constraint
0 = Δqi for minimum quad offset constraint
Fit quad and BPM offsets and implementRepeat BBA procedure
Fit solution for Δy arbitrary to adding linear function to quad and BPM offsets
14 Heinz-Dieter [email protected]
14Undulator CommissioningAugust 2009 FEL2009
BBA Result
Measured Trajectories 4th IterationMeasured Trajectories 4th Iteration
Position rms 2 – 6 μmPosition rms 2 – 6 μm
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15Undulator CommissioningAugust 2009 FEL2009
BBA Results
Fit with Linear Quad ConstraintFit with Linear Quad Constraint
Offset Error Bar 10 μmOffset Error Bar 10 μm
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16Undulator CommissioningAugust 2009 FEL2009
Quad Position/Kick Comparison
Quadrupole positions relative to the electron beam measured by changing the quadrupole gradient and fitting the kick angle. Kick angles are converted to field integrals between quads.As reference undulator segment first field integral tolerance is ±40 µTm .
Fitted 1st Field Integrals
Undulator 1st Field Integral Tolerance: ±40 µTm
Measured Quad Center Displacement to BBA Beam
17 Heinz-Dieter [email protected]
17Undulator CommissioningAugust 2009 FEL2009
Estimated Result of “Quad BBA”
Estimate of the trajectory if instead of energy-dependent BBA the quadrupoles would have been moved to center them on the beam.The resulting trajectory is not dissimilar to the one we use to suppress FEL lasing. This illustrates the need for energy-dependent BBA!
18 Heinz-Dieter [email protected]
18Undulator CommissioningAugust 2009 FEL2009
Girder Stability : Position / Temperature
Girder component motion and undulator temperature variation change
the electron beam trajectory (phase errors) due to changing quadrupole offsets
the undulator strength, which depends on temperature
beam trajectory
Good News: Observed stability of quad positions and undulator temperatures is better than expected.
Girder component motion and undulator temperature variation change
the electron beam trajectory (phase errors) due to changing quadrupole offsets
the undulator strength, which depends on temperature
beam trajectory
Good News: Observed stability of quad positions and undulator temperatures is better than expected.
19 Heinz-Dieter [email protected]
19Undulator CommissioningAugust 2009 FEL2009
QU05 Stability Over 68-Hour Period
Alignment Diagnostics System (ADS)Alignment Diagnostics System (ADS)
1 µm
24 hours
Ali
gn
me
nt
Dia
gn
ost
ics
Sys
tem
(A
DS
)A
lig
nm
en
t D
iag
no
stic
s S
yste
m (
AD
S) 1 µm
24 hours
Horizontal Quad PositionHorizontal Quad Position
Vertical Quad PositionVertical Quad Position
The ADS is based on (1) two 140-m-long stretched wires carrying a 140 MHz RF signal observed by four wire position monitors (WPMs) per girder and (2) a global water level system (HLS), also with four monitors per girder.
The system has a 100 nm resolution.
The combined information from both subsystems is processed and continuously recorded.
The graph shows, as an example, the recording of a 68-hour period during which no girder or segment was moved.
The ADS is based on (1) two 140-m-long stretched wires carrying a 140 MHz RF signal observed by four wire position monitors (WPMs) per girder and (2) a global water level system (HLS), also with four monitors per girder.
The system has a 100 nm resolution.
The combined information from both subsystems is processed and continuously recorded.
The graph shows, as an example, the recording of a 68-hour period during which no girder or segment was moved.
Quad Position Stability Tolerance 1 µm rmsQuad Position Stability Tolerance 1 µm rms
20 Heinz-Dieter [email protected]
20Undulator CommissioningAugust 2009 FEL2009
U16 Temperature Stability over 15 day Period
50 mK
24 hours
Tunnel Lights On
Temperatures are monitoredwith 12 sensors per girder
J. Welch presented poster about temperature control on Tuesday: TUPC53
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21Undulator CommissioningAugust 2009 FEL2009
Segmented Undulator Pre-Taper
22 Heinz-Dieter [email protected]
22Undulator CommissioningAugust 2009 FEL2009
Neutral; K=3.4881; x= 0.0 mm Neutral; K=3.4881; x= 0.0 mmNeutral; K=3.4881; x= 0.0 mm
Undulator Roll-Away and K Adjustment
First; K=3.5000; x=-4.0 mm Roll-Away; K=0.0000; x=+80.0 mm
Horizontal SlideHorizontal Slide
Pole Center LinePole Center Line Vacuum ChamberVacuum Chamber
23 Heinz-Dieter [email protected]
23Undulator CommissioningAugust 2009 FEL2009
Segmented Undulator K Control
K ADJUSTMENT RANGE(MEASURED)
TEMPERATURE CORRECTED KACT
TAPER REQUEST
K ADJUSTMENT RANGE(MEASURED)
24 Heinz-Dieter [email protected]
24Undulator CommissioningAugust 2009 FEL2009
Checking Undulator K Using YAG Luminescence*
3rd harmonic ofSpontaneous
UndulatorRadiation on YAG
Crystal
Ee = 11.1 GeV
Ee = 11.3 GeV
Ee = 11.5 GeV
Ee = 11.7 GeV
Ee = 11.9 GeV
SpontaneousRadiation from
Dump Bend
Yttrium K Edge at 17.038 keVequals 3rd harmonic of undulator
radiation at 11.286 GeV
*by J. Welch and J. Frisch
Kmax =3.4256
Kmin =3.3532
Kavg =3.4616
Expected Kund = 3.4926±0.0005
More precise bracketing gives Kavg =3.4932±0.0045 (1.7 ×10-4 from expected value)
For detailed K measurements see talk by J. Welch in this session: THOA05
25 Heinz-Dieter [email protected]
25Undulator CommissioningAugust 2009 FEL2009
Undulator Characterization: 1st Field Integral U09
Beam Based Measurements
Horizontal (I1X) and vertical (I1Y) first field integrals measured by fitting a kick to the difference trajectory as function of undulator displacement
Reference Point
MMF Measurement
Re
qu
ire
s 2
0 n
m B
PM
re
so
luti
on
26 Heinz-Dieter [email protected]
26Undulator CommissioningAugust 2009 FEL2009
Radiation Control and Monitoring
Undulator radiation damage is greatly reduced through Machine Protection System (MPS) interlocks that inhibit beam to the undulator hall when
BLM (38 monitors) signals are above threshold
Beam loss fiber signals are above threshold
Horizontal and/or vertical trajectory is outside ±1mm
Comparator toroids indicate beam loss.
Any of the upstream profile monitors is inserted
More than 1 BFW is inserted or a BFW is moving
A regular TLD monitoring program is in place
Undulator radiation damage is greatly reduced through Machine Protection System (MPS) interlocks that inhibit beam to the undulator hall when
BLM (38 monitors) signals are above threshold
Beam loss fiber signals are above threshold
Horizontal and/or vertical trajectory is outside ±1mm
Comparator toroids indicate beam loss.
Any of the upstream profile monitors is inserted
More than 1 BFW is inserted or a BFW is moving
A regular TLD monitoring program is in place
27 Heinz-Dieter [email protected]
27Undulator CommissioningAugust 2009 FEL2009
TLD Readings at First Undulator
LOCATION WEEK 1 PHOTON [rad] WEEK 2 PHOTON [rad] WEEK 3 PHOTON [rad]
U25:ANL-BLM 0.081 0.106 0.051
U25: PEP-BLM 0.042 0.048 0.030
U25: Back +X 0.065 0.008 0.033
U25: Back +Y 0.012 0.071 0.064
U25: Back -X 0.039 0.026 0.029
U25: Back +Y 0.013 0.042 0.014
U25: Front +X 0.112 0.093 0.072
U25: Front +Y 0.217 0.105 0.110
U25: Front -X 0.046 0.055 0.025
U25: Front -Y 0.141 0.123 0.093
Recorder Photon Doses about 0.1 rad per weekRecorder Photon Doses about 0.1 rad per week
28 Heinz-Dieter [email protected]
28Undulator CommissioningAugust 2009 FEL2009
Dose During Initial FEL Operation
e-folding length 8.7 me-folding length 8.7 m
Increased TLD Readings are expected to be predominantly low energy synchrotron radiation, not to cause significant magnet damageIncreased TLD Readings are expected to be predominantly low energy synchrotron radiation, not to cause significant magnet damage
[rad
]
29 Heinz-Dieter [email protected]
29Undulator CommissioningAugust 2009 FEL2009
SN20 Radiation Damage Test
HAS BEEN INSTALLED ON GIRDER 33 DURING FEL OPERATION
NO NOTICABLE CHANGE IN FIELD PROPERTIESDURING 2 MONTH OF FEL OPERATON
NO NOTICABLE CHANGE IN FIELD PROPERTIESDURING 2 MONTH OF FEL OPERATON
±40 µTm±40 µTm
TolTol
±50 µTm2±50 µTm2
±40 µTm±40 µTm
±10°±10°
±10°±10°
±10°±10°
±50 µTm2±50 µTm2
±10°±10°
±15×10-5±15×10-5
30 Heinz-Dieter [email protected]
30Undulator CommissioningAugust 2009 FEL2009
Alignment Tolerance Verification
Random misalignment with flat distribution of widh ±a => rms distribution a/sqrt(3)
Beam Based Measurements
31 Heinz-Dieter [email protected]
31Undulator CommissioningAugust 2009 FEL2009
Beam Based K Tolerance Verification
Beam Based Measurements
32 Heinz-Dieter [email protected]
32Undulator CommissioningAugust 2009 FEL2009
LCLS Undulator Tolerance Budget
Error Source i fi i fi Units
@ 130 m (24.2% red.)
Hor/Ver Optics Mismatch (-1)0.5 0.71 0.452 0.32
Hor/Ver Transverse Beam Offset 30 0.176 3.7 µm
Module Detuning K/K 0.060 0.400 0.024 %
Module Offset in x 1121 0.125 140 µm
Module Offset in y 268 0.298 80 µm
Quadrupole Gradient Error 8.8 0.029 0.25 %
Transverse Quadrupole Offset 4.7 0.214 1.0 µm
Break Length Error 20.3 0.049 1.0 mm
21
2
0
ifPe
P
21
2
0
ifPe
P
Tolerance Budget ComponentsTolerance Budget Components
Module Offset in x @ zSAT 780 µm
BB VerificationBB Verification
0.060.06
12001200
8.88.8
770770
MEASUREMENTSMEASUREMENTS
33 Heinz-Dieter [email protected]
33Undulator CommissioningAugust 2009 FEL2009
LCLS undulator system is successfully commissioned.Initial beam operation went extremely smoothly: no tweaking requiredBBA procedure is successfully implemented
Converges to ~1 μm trajectory rmsImportant to have full energy range (4.30 GeV – 13.64 GeV)BBA complemented by measurement of quad offsets by varying quad strength
Temperature and girder stability are well within toleranceBeam loss control and radiation monitoring is in placeHigh radiation levels observed during FEL operation are predominantly low energy photons that are not expected generate demagnetizationVery low dose levels measured at electronics componentsSeveral undulator tolerances could be verified with beam based measurements
LCLS undulator system is successfully commissioned.Initial beam operation went extremely smoothly: no tweaking requiredBBA procedure is successfully implemented
Converges to ~1 μm trajectory rmsImportant to have full energy range (4.30 GeV – 13.64 GeV)BBA complemented by measurement of quad offsets by varying quad strength
Temperature and girder stability are well within toleranceBeam loss control and radiation monitoring is in placeHigh radiation levels observed during FEL operation are predominantly low energy photons that are not expected generate demagnetizationVery low dose levels measured at electronics componentsSeveral undulator tolerances could be verified with beam based measurements
Summary
34 Heinz-Dieter [email protected]
34Undulator CommissioningAugust 2009 FEL2009
The dedicated operations, metrology, engineering, controls, installation, and RF groups at SLACSLAC
The tremendous ANLANL undulator and BPM teamThe extraordinary commissioning teamJohn Galayda (project director) for his leadershipAnd many of you, who have contributed your ideas
Thanks to…