1 Heinz-Dieter Nuhn [email protected] 1 Undulator Commissioning August 2009 FEL2009 Undulator Commissioning, Alignment and Performance Heinz-Dieter

1 Heinz-Dieter [email protected]

1Undulator CommissioningAugust 2009 FEL2009

Undulator Commissioning, Alignment and PerformanceHeinz-Dieter Nuhn – LCLS Undulator Group Leader

August 27, 2009



All 33 Undulator Segments Operational



Girder Components

Quadrupole and horz/vert Correctors

BFWUndulator Segment

Girder

Segment Slider

Girder Mover (cam)

RF Cavity BPM

HLS Sensor

Part of WPM Support



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.



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).



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



Beam Finder Wire

Electron ScatteringXray Scattering



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



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)



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



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



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



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



BBA Result

Measured Trajectories 4th IterationMeasured Trajectories 4th Iteration

Position rms 2 – 6 μmPosition rms 2 – 6 μm



BBA Results

Fit with Linear Quad ConstraintFit with Linear Quad Constraint

Offset Error Bar 10 μmOffset Error Bar 10 μm



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



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!



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.



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



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



Segmented Undulator Pre-Taper



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



Segmented Undulator K Control

K ADJUSTMENT RANGE(MEASURED)

TEMPERATURE CORRECTED KACT

TAPER REQUEST

K ADJUSTMENT RANGE(MEASURED)



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



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



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



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



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

]



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



Alignment Tolerance Verification

Random misalignment with flat distribution of widh ±a => rms distribution a/sqrt(3)




Beam Based K Tolerance Verification




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



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



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…

Documents

1 Heinz-Dieter Nuhn [email protected] 1 Undulator Commissioning August 2009 FEL2009 Undulator Commissioning, Alignment and Performance Heinz-Dieter