Undulator Specifications Heinz-Dieter Nuhn, SLAC / SSRL November 14, 2003

Undulator Parameter Workshop, November 14, 2003Undulator Parameter Workshop, November 14, 2003 Heinz-Dieter Nuhn, SLAC / SSRLHeinz-Dieter Nuhn, SLAC / SSRL

Undulator SpecificationsUndulator Specifications [email protected]@slac.stanford.edu

Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center

Undulator SpecificationsHeinz-Dieter Nuhn, SLAC / SSRL

November 14, 2003

Undulator SpecificationsHeinz-Dieter Nuhn, SLAC / SSRL

November 14, 2003

Undulator OverviewUndulator Overview FEL Performance AssessmentFEL Performance Assessment Recent Undulator Parameter ChangesRecent Undulator Parameter Changes

Undulator OverviewUndulator Overview FEL Performance AssessmentFEL Performance Assessment Recent Undulator Parameter ChangesRecent Undulator Parameter Changes




Linac Coherent Light Source

Near Hall

Far Hall

Undulator




UNDULATOR

3,410 406

11,905 mm

Horizontal Steering Coil

Vertical Steering Coil

Beam Position Monitor

863 mm

X-Ray Diagnostics

Quadrupoles

LCLS Undulator Schematic (Regular Section)LCLS Undulator Schematic (Regular Section)LCLS Undulator Schematic (Regular Section)LCLS Undulator Schematic (Regular Section)

130,092 mmTotal Length




SASE FEL theory well developedSASE FEL theory well developed

and verified by simulationsand verified by simulations

FEL radiation starts from noise in FEL radiation starts from noise in spontaneous radiation spontaneous radiation

Transverse radiation electric Transverse radiation electric field modulates the energy and field modulates the energy and bunches the electrons within an bunches the electrons within an optical wavelengthoptical wavelength

Exponential build-up of radiation Exponential build-up of radiation along undulator lengthalong undulator length

SASE FELsSASE FELs

Undulator RegimeUndulator Regime

Exponential Gain Regime

Exponential Gain Regime

Saturation

Saturation

1 % of X-Ray Pulse1 % of X-Ray Pulse

Electron BunchMicro-Bunching

Electron BunchMicro-Bunching




Expected PerformanceExpected Performance

Low charge cases are modeled in PARMELALow charge cases are modeled in PARMELAafter the GTF results and then imported into after the GTF results and then imported into ELEGANT/GENESIS for the transportELEGANT/GENESIS for the transportthrough the LCLS beam line. through the LCLS beam line.

The simulations includes:The simulations includes:

Space charge in the gunSpace charge in the gun

Emittance compensationEmittance compensation

Wakefield and CSR effects Wakefield and CSR effects

Optimized beam transport (Jitter)Optimized beam transport (Jitter)

Spontaneous Undulator Radiation Spontaneous Undulator Radiation

Low charge cases are modeled in PARMELALow charge cases are modeled in PARMELAafter the GTF results and then imported into after the GTF results and then imported into ELEGANT/GENESIS for the transportELEGANT/GENESIS for the transportthrough the LCLS beam line. through the LCLS beam line.

The simulations includes:The simulations includes:

Space charge in the gunSpace charge in the gun

Emittance compensationEmittance compensation

Wakefield and CSR effects Wakefield and CSR effects

Optimized beam transport (Jitter)Optimized beam transport (Jitter)

Spontaneous Undulator Radiation Spontaneous Undulator Radiation

All cases reach saturationAll cases reach saturation

ParmelaParmelaParmelaParmela ElegantElegantElegantElegant Genesis / GingerGenesis / GingerGenesis / GingerGenesis / Ginger

space-chargespace-charge compression, wakes, CSR, …compression, wakes, CSR, … SASE FEL with wakesSASE FEL with wakes

Start-To-End Simulations:Start-To-End Simulations:




Workshop on Start-To-End SimulationsWorkshop on Start-To-End Simulations

Beam Dynamics Mini WorkshopFuture Light Sources

Start-To-End Simulations for SASE FELs (S2E 2003)Chaired by

John Galayda (SLAC) and Joerg Rossbach (DESY)

Dates

August 18 – 22, 2003

Location

DESY-Zeuthen, Berlin, Germany




Comparison of GINGER/GENESIS resultsfor 1-nC LCLS “0-order” Case

Comparison of GINGER/GENESIS resultsfor 1-nC LCLS “0-order” Case

Observations:• GENESIS shows very slightly longer gain

length, later saturation but higher power• GINGER shows stronger post-saturation

power oscillation (more deeply trapped particles?)

• Method for choosing best K was slightly different for both codes




GINGER/GENESIS results for “0-order” 200-pC case

GINGER/GENESIS results for “0-order” 200-pC case

Observations:• Again, GENESIS shows slightly longer

gain length, 10-m later saturation but 15% higher power

• Again, GINGER shows deeper post-saturation power oscillation

• Little sensitivity (2 m, 7%) in GINGER results to 8X particle number increase

• Possible reasons for differences: bugs slight differences in initial e-beam

properties (e.g. mismatch) grid effects (e.g. outer boundary)???




1-nC LCLS: “1st-order” envelope reconstruction: max P(z) vs. slice time1-nC LCLS: “1st-order” envelope reconstruction: max P(z) vs. slice time

100 GW100 GW

Some quick observations:• Power suppressed in regions with high energy spread [-90:-70 fs]• GENESIS shows ~2-3X greater power than GINGER for no-wake

cases• For runs including wake fields, GINGER shows somewhat more peak

power for the main body (but more localized in time)• Beam centroid wander may be important – better modeled by

GENESIS

GINGER GENESIS




Tolerance Analysis: Tolerance Analysis: RONRONR. Dejus, N. VinokurovR. Dejus, N. VinokurovTolerance Analysis: Tolerance Analysis: RONRONR. Dejus, N. VinokurovR. Dejus, N. Vinokurov




Undulator Performance Requirements (as of May 2003)Undulator Performance Requirements (as of May 2003)

ParameterParameter SymbolSymbol TargetTarget

(Nom.)(Nom.)UnitsUnits ToleranceTolerance

((criticalcritical))

Effective Undulator ParameterEffective Undulator Parameter KK 3.7113.711 ±0.015 ±0.015 %%

Average Gap HeightAverage Gap Height gg 6.06.0 mmmm +0.006+0.006

Average Period LengthAverage Period Length uu 30.0030.00 mmmm ±0.03±0.03

Wiggle PlaneWiggle Plane horizontalhorizontal ——

RMS Trajectory Straightness ToleranceRMS Trajectory Straightness Tolerance xx 22 mm ——

RMS Segment Phase Shake ToleranceRMS Segment Phase Shake Tolerance 1010 degreesdegrees ——

3.6350 3.6350 6.56.5




Trajectory Straightness RequirementTrajectory Straightness RequirementTrajectory Straightness RequirementTrajectory Straightness Requirement

Preserve transverse overlap between beam and Preserve transverse overlap between beam and radiationradiation => Tolerance for betatron amplitude < 8 => Tolerance for betatron amplitude < 8 m (beam radius m (beam radius

dep.)dep.)

Avoid longitudinal phase shake between beam and Avoid longitudinal phase shake between beam and radiationradiation

=> Tolerance for rms phase shake 10 degrees per module=> Tolerance for rms phase shake 10 degrees per module

=> Equivalent tolerance for rms electron beam straightness 2 => Equivalent tolerance for rms electron beam straightness 2 m m

Preserve transverse overlap between beam and Preserve transverse overlap between beam and radiationradiation => Tolerance for betatron amplitude < 8 => Tolerance for betatron amplitude < 8 m (beam radius m (beam radius

dep.)dep.)

Avoid longitudinal phase shake between beam and Avoid longitudinal phase shake between beam and radiationradiation

=> Tolerance for rms phase shake 10 degrees per module=> Tolerance for rms phase shake 10 degrees per module

=> Equivalent tolerance for rms electron beam straightness 2 => Equivalent tolerance for rms electron beam straightness 2 m m




Workshop on Undulator ParametersWorkshop on Undulator Parameters

LCLS Undulator Parameter WorkshopChaired by

Heinz-Dieter Nuhn (SLAC)

Dates

November 24, 2003

Location

APS, Argonne, USA




Workshop FocusWorkshop FocusWorkshop FocusWorkshop Focus

Set Undulator PeriodSet Undulator Period

Reduction of maximum available linac energyReduction of maximum available linac energy

Undulator gap height increaseUndulator gap height increase

Longer break distancesLonger break distances

Weaker FODO latticeWeaker FODO lattice

Set Undulator PeriodSet Undulator Period

Reduction of maximum available linac energyReduction of maximum available linac energy

Undulator gap height increaseUndulator gap height increase

Longer break distancesLonger break distances

Weaker FODO latticeWeaker FODO lattice




Halbach formula for hybrid undulator is used to Halbach formula for hybrid undulator is used to estimate relation between gap/period and on-axis estimate relation between gap/period and on-axis fieldfield

Measured prototype field 5.3% larger than estimatedMeasured prototype field 5.3% larger than estimated

Halbach formula for hybrid undulator is used to Halbach formula for hybrid undulator is used to estimate relation between gap/period and on-axis estimate relation between gap/period and on-axis fieldfield

Measured prototype field 5.3% larger than estimatedMeasured prototype field 5.3% larger than estimated

Adjusting Estimate of On-Axis Undulator FieldAdjusting Estimate of On-Axis Undulator FieldAdjusting Estimate of On-Axis Undulator FieldAdjusting Estimate of On-Axis Undulator Field

2gap gap

b cperiod periodB a e

3.44 T

5.08

1.54

a

b

c

3 cm1.325 T

6.00 mm

periodB

gap

6.35

3 cm1.325 T

mm

periodB

gap

5.08

1.5

3.6

4

2 Ta

b

c




Undulator PeriodUndulator PeriodUndulator PeriodUndulator Period

Present undulator period length of 3 cm is near Present undulator period length of 3 cm is near optimum for shortest gain lengthoptimum for shortest gain length

Change of undulator period length would require more Change of undulator period length would require more man-power and time than available before next reviewman-power and time than available before next review

Undulator period length will be kept at Undulator period length will be kept at

uu = 3.0 cm = 3.0 cm

Present undulator period length of 3 cm is near Present undulator period length of 3 cm is near optimum for shortest gain lengthoptimum for shortest gain length

Change of undulator period length would require more Change of undulator period length would require more man-power and time than available before next reviewman-power and time than available before next review

Undulator period length will be kept at Undulator period length will be kept at

uu = 3.0 cm = 3.0 cm




Maximum Available Linac EnergyMaximum Available Linac EnergyMaximum Available Linac EnergyMaximum Available Linac Energy

14.35 GeV has been nominal energy to reach 1.5 Å14.35 GeV has been nominal energy to reach 1.5 Å

Loss of available linac energy due toLoss of available linac energy due to Reduction of available linac sections (incl. Injector Reduction of available linac sections (incl. Injector

relocation)relocation)

Off-crest accelerationOff-crest acceleration

New maximum energy set to 14.1 GeV to restore New maximum energy set to 14.1 GeV to restore operational overheadoperational overhead

Requires change in K valueRequires change in K value

14.35 GeV has been nominal energy to reach 1.5 Å14.35 GeV has been nominal energy to reach 1.5 Å

Loss of available linac energy due toLoss of available linac energy due to Reduction of available linac sections (incl. Injector Reduction of available linac sections (incl. Injector

relocation)relocation)

Off-crest accelerationOff-crest acceleration

New maximum energy set to 14.1 GeV to restore New maximum energy set to 14.1 GeV to restore operational overheadoperational overhead

Requires change in K valueRequires change in K value




Undulator Gap SelectionUndulator Gap SelectionUndulator Gap SelectionUndulator Gap Selection

Undulator gap height changes still possibleUndulator gap height changes still possible

Present gap height: 6 mmPresent gap height: 6 mm

Gap height corrected for measured field: 6.35 mmGap height corrected for measured field: 6.35 mm

Parameter correction for reduced maximum energyParameter correction for reduced maximum energy

Larger gap gives access to short wavelength 1.0 ÅLarger gap gives access to short wavelength 1.0 Å

Undulator gap height changes still possibleUndulator gap height changes still possible

Present gap height: 6 mmPresent gap height: 6 mm

Gap height corrected for measured field: 6.35 mmGap height corrected for measured field: 6.35 mm

Parameter correction for reduced maximum energyParameter correction for reduced maximum energy

Larger gap gives access to short wavelength 1.0 ÅLarger gap gives access to short wavelength 1.0 Å

max

6.5 mm

1.298 T

3.6350

gap

B

K

14.09 GeV 1.5 Å

4.46 GeV 15.0 År

r

E

E

max

8.2 mm

1.013 T

2.838

gap

B

K

14.03 GeV 1.0 Å

11.46 GeV 1.5 Å

3.62 GeV 15.0 Å

r

r

r

E

E

E

New ParametersNew ParametersNew ParametersNew Parameters

Rejected

Rejected

Rejected

Rejected

More Room for Vacuum Chamber

More Room for Vacuum Chamber




LCLS Undulator Large Gap / Low K ProposalLCLS Undulator Large Gap / Low K Proposal

Proposed Proposed Undulator Undulator

LengthLength

Emittance Emittance GoalGoal

Safety Safety OverheadOverhead

Emittance Emittance AchievedAchieved

Based on Based on Chosen Chosen

ParametersParameters




New Break LengthsNew Break LengthsNew Break LengthsNew Break Lengths

Separations between undulator modules (breaks) designed to Separations between undulator modules (breaks) designed to produce slippage by integer number of optical wavelength.produce slippage by integer number of optical wavelength.

Break increments for adding slippage of 1 optical wavelength is Break increments for adding slippage of 1 optical wavelength is LLBB==uu (1+K (1+K22/2). /2).

LLBB=23.7 cm (old); 22.8 cm (new)=23.7 cm (old); 22.8 cm (new) Present design uses break pattern 1-1-2 which corresponds to Present design uses break pattern 1-1-2 which corresponds to

the lengths sequence the lengths sequence 18.7 cm – 18.7 cm – 42.1 cm 18.7 cm – 18.7 cm – 42.1 cm

18.7 cm gives not enough space for quads, BPMs, etc.18.7 cm gives not enough space for quads, BPMs, etc. Length needed > 30 cm Length needed > 30 cm 42.1 cm gives not enough space for x-ray diagnostics42.1 cm gives not enough space for x-ray diagnostics Length needed > 70 cm Length needed > 70 cm

New break pattern 2-2-4 corresponding to lengthNew break pattern 2-2-4 corresponding to lengthsequence 40.6 cm – 40.6 cm – 86.3 cmsequence 40.6 cm – 40.6 cm – 86.3 cm

Separations between undulator modules (breaks) designed to Separations between undulator modules (breaks) designed to produce slippage by integer number of optical wavelength.produce slippage by integer number of optical wavelength.

Break increments for adding slippage of 1 optical wavelength is Break increments for adding slippage of 1 optical wavelength is LLBB==uu (1+K (1+K22/2). /2).

LLBB=23.7 cm (old); 22.8 cm (new)=23.7 cm (old); 22.8 cm (new) Present design uses break pattern 1-1-2 which corresponds to Present design uses break pattern 1-1-2 which corresponds to

the lengths sequence the lengths sequence 18.7 cm – 18.7 cm – 42.1 cm 18.7 cm – 18.7 cm – 42.1 cm

18.7 cm gives not enough space for quads, BPMs, etc.18.7 cm gives not enough space for quads, BPMs, etc. Length needed > 30 cm Length needed > 30 cm 42.1 cm gives not enough space for x-ray diagnostics42.1 cm gives not enough space for x-ray diagnostics Length needed > 70 cm Length needed > 70 cm

New break pattern 2-2-4 corresponding to lengthNew break pattern 2-2-4 corresponding to lengthsequence 40.6 cm – 40.6 cm – 86.3 cmsequence 40.6 cm – 40.6 cm – 86.3 cm




Weaker FODO LatticeWeaker FODO LatticeWeaker FODO LatticeWeaker FODO Lattice

FODO Lattice had been designed for FODO Lattice had been designed for < <x,yx,y>=18 m at 1.5 Å >=18 m at 1.5 Å

Required gradient of 106-107 T/m for 5 cm long quadsRequired gradient of 106-107 T/m for 5 cm long quads

New gradient set to 60 T/m toNew gradient set to 60 T/m to Increase Saturation PowerIncrease Saturation Power

Relax Beam-Based Alignment TolerancesRelax Beam-Based Alignment Tolerances

Saturation length only slightly increasedSaturation length only slightly increased

Average beta function at 1.5 Å is nowAverage beta function at 1.5 Å is now < <x,yx,y>=30 m>=30 m

Focusing and defocusing magnets will be identicalFocusing and defocusing magnets will be identical

FODO Lattice had been designed for FODO Lattice had been designed for < <x,yx,y>=18 m at 1.5 Å >=18 m at 1.5 Å

Required gradient of 106-107 T/m for 5 cm long quadsRequired gradient of 106-107 T/m for 5 cm long quads

New gradient set to 60 T/m toNew gradient set to 60 T/m to Increase Saturation PowerIncrease Saturation Power

Relax Beam-Based Alignment TolerancesRelax Beam-Based Alignment Tolerances

Saturation length only slightly increasedSaturation length only slightly increased

Average beta function at 1.5 Å is nowAverage beta function at 1.5 Å is now < <x,yx,y>=30 m>=30 m

Focusing and defocusing magnets will be identicalFocusing and defocusing magnets will be identical




LCLS Optimum -Function at Short Wavelength LCLS Optimum -Function at Short Wavelength

Optimum Beta-FunctionOptimum Beta-Function

New Beta-FunctionNew Beta-Function

14.1 GeV 14.1 GeV




LCLS Operating Points for 1 nC Bunch Charge (Old)LCLS Operating Points for 1 nC Bunch Charge (Old)

LCLS Operating Point at LCLS Operating Point at 1.5 Å1.5 ÅLCLS Operating Point at LCLS Operating Point at 1.5 Å1.5 Å LCLS Operating Point at LCLS Operating Point at 15 Å15 ÅLCLS Operating Point at LCLS Operating Point at 15 Å15 Å




LCLS Operating Points for 1 nC Bunch Charge (New)LCLS Operating Points for 1 nC Bunch Charge (New)

LCLS Operating Point at LCLS Operating Point at 1.5 Å1.5 ÅLCLS Operating Point at LCLS Operating Point at 1.5 Å1.5 Å

Operating PointOperating Point Operating PointOperating Point




LCLS Operating Points for 1 nC Bunch Charge (New)LCLS Operating Points for 1 nC Bunch Charge (New)

LCLS Operating Point at LCLS Operating Point at 15 Å15 ÅLCLS Operating Point at LCLS Operating Point at 15 Å15 Å

Operating PointOperating PointOperating PointOperating Point




Beam Based Alignment Tolerances (Paul Emma)Beam Based Alignment Tolerances (Paul Emma)

0.040.04

00 44

100100

100100

22




OLD NEWUndulator Type planar hybrid planar hybridMagnet Material NdFeB NdFeBWiggle Plane horizontal horizontalGap 6 6.5

mmPeriod Length 3.0 3.0 cmPeak On-Axis Field 1.325 1.298 TK 3.711 2.635

Module Length 3.41 3.41 mNumber of Modules 33 33Undulator Magnet Length 112.5 112.5 m

Break Length 18.7-18.7-42.1 40.6-40.6-86.3 cmTotal Device Length 121.8 130.2 m

OLD NEWUndulator Type planar hybrid planar hybridMagnet Material NdFeB NdFeBWiggle Plane horizontal horizontalGap 6 6.5

mmPeriod Length 3.0 3.0 cmPeak On-Axis Field 1.325 1.298 TK 3.711 2.635

Module Length 3.41 3.41 mNumber of Modules 33 33Undulator Magnet Length 112.5 112.5 m

Break Length 18.7-18.7-42.1 40.6-40.6-86.3 cmTotal Device Length 121.8 130.2 m

Summary of Nominal Undulator Design ChangesSummary of Nominal Undulator Design Changes




OLD NEW

Lattice Type FODO FODOMagnet Type permanent permanentNominal Magnet Length 5 5 cmQF Gradient 107 60 T/mQD Gradient -106 -60 T/mAverage Function at 1.5 Å 18.0 30 mLowest Usable Energy 3.17 1.84 GeV

OLD NEW

Lattice Type FODO FODOMagnet Type permanent permanentNominal Magnet Length 5 5 cmQF Gradient 107 60 T/mQD Gradient -106 -60 T/mAverage Function at 1.5 Å 18.0 30 mLowest Usable Energy 3.17 1.84 GeV

Summary of Nominal Focusing Lattice ChangesSummary of Nominal Focusing Lattice Changes




Summary of Electron Beam ParametersSummary of Electron Beam Parameters

At 15 Å OLD NEW

Electron Beam Energy 4.45 4.46 GeV 8880 8722<> 7.3 8.9

mrms beam radius 35 34 m

At 15 Å OLD NEW



At 1.5 Å OLD NEW



At 1.5 Å OLD NEW






ConclusionsConclusions

Requirements for LCLS undulator are well establishedRequirements for LCLS undulator are well establishedLCLS undulator performance requirements are well understoodLCLS undulator performance requirements are well understoodRisks have been assessed and undulator specifications address the riskRisks have been assessed and undulator specifications address the riskNew parameter values have been chosenNew parameter values have been chosen

Increase in undulator gap, Increase in undulator gap, reduction in maximum electron beam energy, reduction in maximum electron beam energy, longer break length, and longer break length, and reduced quadrupole gradientsreduced quadrupole gradients

Benefits areBenefits aremore room for vacuum chambermore room for vacuum chambermore energy safety marginmore energy safety marginmore space for diagnostics components between undulator modulesmore space for diagnostics components between undulator modulesincrease of accessible wavelength rangeincrease of accessible wavelength range

Requirements for LCLS undulator are well establishedRequirements for LCLS undulator are well establishedLCLS undulator performance requirements are well understoodLCLS undulator performance requirements are well understoodRisks have been assessed and undulator specifications address the riskRisks have been assessed and undulator specifications address the riskNew parameter values have been chosenNew parameter values have been chosen

Increase in undulator gap, Increase in undulator gap, reduction in maximum electron beam energy, reduction in maximum electron beam energy, longer break length, and longer break length, and reduced quadrupole gradientsreduced quadrupole gradients

Benefits areBenefits aremore room for vacuum chambermore room for vacuum chambermore energy safety marginmore energy safety marginmore space for diagnostics components between undulator modulesmore space for diagnostics components between undulator modulesincrease of accessible wavelength rangeincrease of accessible wavelength range




End of Presentation

Documents

Undulator Specifications Heinz-Dieter Nuhn, SLAC / SSRL November 14, 2003