Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting [email protected] Undulator Physics

Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLSFacility Advisory Committee Meeting [email protected]@slac.stanford.edu

Undulator Physics Requirementsand Alignment

Heinz-Dieter Nuhn, SLAC / LCLSApril 7, 2005

Undulator Physics Requirementsand Alignment

Heinz-Dieter Nuhn, SLAC / LCLSApril 7, 2005

Final Break Length Choice

Mitigation of AC Conductivity Wakefield Effects

Undulator Tolerance Budget Considerations

Cradle Component Arrangement and Alignment

Earth Magnetic Field Compensation

Radiation Damage Calculations

Final Break Length Choice

Mitigation of AC Conductivity Wakefield Effects

Undulator Tolerance Budget Considerations

Cradle Component Arrangement and Alignment

Earth Magnetic Field Compensation

Radiation Damage Calculations


Undulator Break LengthsUndulator Break LengthsOld StrategyOld Strategy

Characteristic Lengths Length of Undulator Strongback (Segment):

Lseg = 3.4 m

Distance for 113 x 2 Phase Slippage:L0 = 3.668 m

Distance for 2 Phase Slippage in Field Free Space:Linc = u (1+K2/2) = 0.214 m

Standard Break Lengths Used Use parameter n to characterize different phase length choices

Ln = L0 - Lseg +(n-1)Linc

Use 2 Short Breaks Followed by 1 Long Break in n-Pattern2 – 2 – 4 [0.482 m – 0.482 m – 0.910 m]

Fine Tuning of Initial Break Length Suggested by N. Vinokurov based on Simulations by R. Dejus and N. Vinokurov

using Linear Simulation Code, RON

Small length increases for first 3 break lengths[0.045 m – 0.020 m – 0.005 m]

Total Undulator Length (from beginning of strongback 1 – end of strongback 33):

Lund = 131.97 m


Lseg = 3.4 m

Distance for 113 x 2 Phase Slippage:L0 = 3.668 m




Use 2 Short Breaks Followed by 1 Long Break in n-Pattern2 – 2 – 4 [0.482 m – 0.482 m – 0.910 m]





Lund = 131.97 m


Undulator Break LengthsUndulator Break LengthsGINGER Simulation SummaryGINGER Simulation Summary

As undulator gets closer to construction phase lock-down of segment spacing is required.

R. Dejus requests checking of RON results with nonlinear FEL simulation codes before break length distances are being frozen.

Phase correction scheme was tested recently by Bill Fawley and Sven Reiche using non-linear FEL codes, GINGER and GENESIS, respectively.

With canted poles, phase corrections can be implemented with K adjustments rather than break lengths adjustments.

The simulations used changes in break length.

As undulator gets closer to construction phase lock-down of segment spacing is required.

R. Dejus requests checking of RON results with nonlinear FEL simulation codes before break length distances are being frozen.

Phase correction scheme was tested recently by Bill Fawley and Sven Reiche using non-linear FEL codes, GINGER and GENESIS, respectively.

With canted poles, phase corrections can be implemented with K adjustments rather than break lengths adjustments.

The simulations used changes in break length.


Undulator Break LengthsUndulator Break Lengths GINGER Simulations Time Domain Results GINGER Simulations Time Domain Results

GINGER Simulations for three different applications of the Vinokurov/Dejus correction Reduced [-0.045 m, -0.020 m, -0.005 m]

Nominal

Increased [+0.045 m, +0.020 m, +0.005 m]

Increased lengths produce slightly more power but no significant change in gain length.

GINGER Simulations for three different applications of the Vinokurov/Dejus correction Reduced [-0.045 m, -0.020 m, -0.005 m]

Nominal

Increased [+0.045 m, +0.020 m, +0.005 m]

Increased lengths produce slightly more power but no significant change in gain length.

William FawleyWilliam Fawley


Undulator Break LengthsUndulator Break Lengths GENESIS Simulations Time Domain Results GENESIS Simulations Time Domain Results

GENESIS results comparable to those from GINGER. GENESIS results comparable to those from GINGER.

Sven ReicheSven Reiche


Undulator Break LengthsUndulator Break Lengths GINGER Simulations Spectrum GINGER Simulations Spectrum

During linear regime uncorrected break pattern gives best results.

Towards end of undulator no significant effect of corrections

General outcome: No need for break in regular break pattern.

New break pattern will consist of 22 short and 10 long break lengths only.

During linear regime uncorrected break pattern gives best results.

Towards end of undulator no significant effect of corrections

General outcome: No need for break in regular break pattern.

New break pattern will consist of 22 short and 10 long break lengths only.

William FawleyWilliam Fawley


Undulator Break LengthsUndulator Break Lengths(Old Strategy)(Old Strategy) New Strategy New Strategy


Lseg = 3.4 m

Distance for 113 x 2 Phase Slippage:L0 = (3.668 m) 3.656 m




Use 2 Short Breaks Followed by 1 Long Break in n-Pattern2 – 2 – 4 ([0.482 m – 0.482 m – 0.910 m]) [0.470 m – 0.470 m –

0.898 m]





Lund = (131.97 m) 131.52 m


Lseg = 3.4 m

Distance for 113 x 2 Phase Slippage:L0 = (3.668 m) 3.656 m




Use 2 Short Breaks Followed by 1 Long Break in n-Pattern2 – 2 – 4 ([0.482 m – 0.482 m – 0.910 m]) [0.470 m – 0.470 m –

0.898 m]





Lund = (131.97 m) 131.52 m


Mitigation of AC-Conductivity Wakefield EffectsMitigation of AC-Conductivity Wakefield Effects

Change Vacuum Pipe Properties(See Bane talk)

Change Surface Material from Copper to Aluminum

Change Cross Section from Round to Oblong (10x5 mm)

Move to Low-Charge Operating Point(see Emma talk)

Use Tapering to Enhance Gain(see Huang talk)

Change Vacuum Pipe Properties(See Bane talk)

Change Surface Material from Copper to Aluminum

Change Cross Section from Round to Oblong (10x5 mm)

Move to Low-Charge Operating Point(see Emma talk)

Use Tapering to Enhance Gain(see Huang talk)


Revisiting the Undulator Tolerance BudgetRevisiting the Undulator Tolerance Budget

Separate budgets exist for undulator tolerancesUndulator Field TuningSegment AlignmentBBAFloor Stability

A Monte Carlo model is being developed which simultaneously includes all of the above errors

Calculates the cumulative phase error with MC statisticsShows the relative importance of different tolerances

Next step is to test putative tolerance budgets against FEL code, including beam tolerances. Answer the question:

For a give overall tolerance budget, what is the probability that the FEL flux will be above 1012 photons/pulse?

Separate budgets exist for undulator tolerancesUndulator Field TuningSegment AlignmentBBAFloor Stability

A Monte Carlo model is being developed which simultaneously includes all of the above errors

Calculates the cumulative phase error with MC statisticsShows the relative importance of different tolerances

Next step is to test putative tolerance budgets against FEL code, including beam tolerances. Answer the question:

For a give overall tolerance budget, what is the probability that the FEL flux will be above 1012 photons/pulse?

Jim WelchJim Welch


Undulator Segment Alignment ToleranceUndulator Segment Alignment Tolerance

Based on K Tolerance

K depends on vertical distance from mid-plane.

Canted poles make K also dependent on horizontal position

Tolerance Amplitudes

Horizontal +/- 180 microns

Vertical +/- 70 microns

Based on K Tolerance

K depends on vertical distance from mid-plane.

Canted poles make K also dependent on horizontal position

Tolerance Amplitudes

Horizontal +/- 180 microns

Vertical +/- 70 microns


Cradle Component Arrangement and AlignmentCradle Component Arrangement and AlignmentProblem CharacterizationProblem Characterization

Two-Fold Problem for Segment Alignment

Initial installation and alignment to a straight line

Alignment maintenance in the presence of ground motion

Two Strategies under Consideration

Cradle Coupling (Train-Link)

Upstream-Downstream Beam Position Monitors

Two-Fold Problem for Segment Alignment

Initial installation and alignment to a straight line

Alignment maintenance in the presence of ground motion

Two Strategies under Consideration

Cradle Coupling (Train-Link)

Upstream-Downstream Beam Position Monitors


Cradle Component Arrangement and AlignmentCradle Component Arrangement and AlignmentProblem DescriptionProblem Description

BBA will only correct alignment of quadrupoles.

Undulator segment alignment is not affected.

Additional alignment strategy needed.

BBA will only correct alignment of quadrupoles.

Undulator segment alignment is not affected.

Additional alignment strategy needed.

Quad

Vertical

Before BBA

After BBA

Before BBA

After BBA

Horizonal


Cradle Component Arrangement and AlignmentCradle Component Arrangement and AlignmentSolution 1: Cradle Coupling (CLIC)Solution 1: Cradle Coupling (CLIC)

Coupling will be adjusted on appropriately designed setup in MMF.

Quadrupole motion during BBA will through coupled cradle motion.

Cradles will be aligned in the process.

Coupling will be adjusted on appropriately designed setup in MMF.

Quadrupole motion during BBA will through coupled cradle motion.

Cradles will be aligned in the process.

Quad

Vertical

Before BBA

After BBA

Before BBA

After BBA

Horizonal


Cradle Component Arrangement and AlignmentCradle Component Arrangement and AlignmentSolution 2: Downstream MonitorSolution 2: Downstream Monitor

Monitor downstream of the undulator, fiducialized to the strongback, will be used to correct undulator alignment after BBA.

Monitor could be RF Cavity BPM (either the one used for BBA or additional) or a pair of wire scanners.

Use of BBA BPM for the strongback alignment restricts freedom in BPM positioning.

Monitor downstream of the undulator, fiducialized to the strongback, will be used to correct undulator alignment after BBA.

Monitor could be RF Cavity BPM (either the one used for BBA or additional) or a pair of wire scanners.

Use of BBA BPM for the strongback alignment restricts freedom in BPM positioning.

Quad

Vertical

Before BBA

After BBA

Before BBA

After BBA

HorizonalMonitor


Cradle Component Arrangement and AlignmentCradle Component Arrangement and AlignmentWinning CandidateWinning Candidate

Monitor (wire scanner) upstream of the undulator fiducialized the strongback to control undulator alignment after BBA .

RF Cavity BPM for BBA mounted next to quadrupole.

Monitor (wire scanner) upstream of the undulator fiducialized the strongback to control undulator alignment after BBA .

RF Cavity BPM for BBA mounted next to quadrupole.

Quad

Vertical

Before BBA

After BBA

Before BBA

After BBA

Horizonal

Monitor

BPM

Beam


Cradle Component Arrangement and AlignmentUndulator – to – Quad Tolerance Budget

Vertical Horizontal [µm] [µm] Quadrupole Fiducials Pulsed Wire Center Definition 10 10 Wire to Wire Finder (WF) Fiducial 20 20 WF Fiducial to Quadrupole Fiducial 10 10 25 25 Quadrupole BBA Offset 20 20 Undulator Fiducials Hall Probe Resolution/Positioning 20 20 Needle Hall Probe Resolution 15 30 Needle Center to Fiducial 20 30 Fixture Fiducial to Undulator Fiducial 20 20 40 50 Undulator Segment Roll-Away Repeatability 5 10 Alignment Quadrupole to Undulator 40 40 Grand Total 65 70

Individual contributions are added in quadratureIndividual contributions are added in quadrature

See R. Ruland Talk for discussion See R. Ruland Talk for discussion


Earth Magnetic Field CompensationEarth Magnetic Field CompensationStrategyStrategy

Earth Magnetic Field along Beam Trajectory in Undulator requires compensation. Estimated strength 0.43±0.06 Gauss : (0.18±0.03, -0.38±0.07,0.08±0.05) Gauss Based on Measurements by K. Hacker. (see LCLS-TN-05-4)

Compensation Strategy:

Position the Undulator on Magnetic Measurement Bench in same direction as in Undulator Tunnel. Add correction field if necessary.

Compensate Earth Field Component in Undulator in Shimming Process

Scheduling Issues

Earth Magnetic Field along Beam Trajectory in Undulator requires compensation. Estimated strength 0.43±0.06 Gauss : (0.18±0.03, -0.38±0.07,0.08±0.05) Gauss Based on Measurements by K. Hacker. (see LCLS-TN-05-4)

Compensation Strategy:

Position the Undulator on Magnetic Measurement Bench in same direction as in Undulator Tunnel. Add correction field if necessary.

Compensate Earth Field Component in Undulator in Shimming Process

Scheduling Issues


Earth Magnetic Field CompensationEarth Magnetic Field CompensationSchedule IssuesSchedule Issues

Milestone Dictionary

07/03/2006 Delivery of Undulator 1st Articles to MMF (MS2_UN010)07/28/2006 27% Production Undulators Received (MS3_UN015)07/28/2006 MMF Qualified & Ready to Measure Prod Undulators (MS3_UN005)08/28/2006 MMF Qualified & Ready to Measure Prod Undulators (MS2_UN005)10/17/2006 50% Production Undulators Received (MS3_UN022)01/03/2007 75% Production Undulators Received (MS3_UN027)03/09/2007 Undulator Production Unit (33) Received (MS3_UN029)05/03/2007 Undulator Facility Beneficial Occupancy (MS3BO_035)07/02/2007 Undulator Facility Beneficial Occupancy (MS2BO_035)07/18/2008 Start Undulator Commissioning (1st Light ) (MS3_UN025)08/18/2008 Start Undulator Commissioning (1st Light ) (MS2_UN025)

Undulator Hall Beneficial Occupancy occurs 2 months after 33rd undulator is received.

Undulator Hall Magnetic Field can not be measured before tuning of most of the undulator segments is complete

Risk that field found in undulator hall is different from field used during shimming.

Tolerance for error field is 0.1 G.

Milestone Dictionary

07/03/2006 Delivery of Undulator 1st Articles to MMF (MS2_UN010)07/28/2006 27% Production Undulators Received (MS3_UN015)07/28/2006 MMF Qualified & Ready to Measure Prod Undulators (MS3_UN005)08/28/2006 MMF Qualified & Ready to Measure Prod Undulators (MS2_UN005)10/17/2006 50% Production Undulators Received (MS3_UN022)01/03/2007 75% Production Undulators Received (MS3_UN027)03/09/2007 Undulator Production Unit (33) Received (MS3_UN029)05/03/2007 Undulator Facility Beneficial Occupancy (MS3BO_035)07/02/2007 Undulator Facility Beneficial Occupancy (MS2BO_035)07/18/2008 Start Undulator Commissioning (1st Light ) (MS3_UN025)08/18/2008 Start Undulator Commissioning (1st Light ) (MS2_UN025)

Undulator Hall Beneficial Occupancy occurs 2 months after 33rd undulator is received.

Undulator Hall Magnetic Field can not be measured before tuning of most of the undulator segments is complete

Risk that field found in undulator hall is different from field used during shimming.

Tolerance for error field is 0.1 G.


0.1-Gauss Earth’s field in 0.1-Gauss Earth’s field in xx-direction – perfect system, quads on, no steering-direction – perfect system, quads on, no steering

Paul EmmaPaul Emma

Earth Magnetic Field Effect on TrajectoryEarth Magnetic Field Effect on Trajectory

0.1-Gauss Earth’s field in 0.1-Gauss Earth’s field in xx-direction – perfect system, after BBA-direction – perfect system, after BBA


0.1-Gauss Earth’s field in 0.1-Gauss Earth’s field in xx-direction – standard errors, after BBA-direction – standard errors, after BBA

no Earth’s field – standard errors, after BBAno Earth’s field – standard errors, after BBA

Paul EmmaPaul Emma






Paul EmmaPaul Emma


Earth Magnetic Field CompensationEarth Magnetic Field CompensationAdjustable Shim ConceptAdjustable Shim Concept

Risk arises from the lack of precise knowledge of the earth field in the tunnel at the time of undulator segment tuning.

Considering mitigation strategy based on use of a small number of precisely adjustable shims along each undulator.

One extra shim per segment will reduce phase error by factor 4.

Shims could be installed before undulator tuning, but adjusted before undulator installation when field errors have been determined.

Will not affect definition of magnetic center of undulator (Standard Undulator Axis, SUSA, [see PRD 1.4-001 4.7])

Risk arises from the lack of precise knowledge of the earth field in the tunnel at the time of undulator segment tuning.

Considering mitigation strategy based on use of a small number of precisely adjustable shims along each undulator.

One extra shim per segment will reduce phase error by factor 4.

Shims could be installed before undulator tuning, but adjusted before undulator installation when field errors have been determined.

Will not affect definition of magnetic center of undulator (Standard Undulator Axis, SUSA, [see PRD 1.4-001 4.7])

Quad QuadBPMBPMUndulator Undulator

Shim Position Trajectory w/ Shim

Trajectory w/o Shim

Quad BPM


Radiation Damage CalculationsRadiation Damage Calculationsfrom Inserted Screenfrom Inserted Screen

Question: Can OTR Screen be used in the LCLS undulator without causing significant radiation damage to the magnets?

Problem Setup and Initial FLUKA Simulations by A. Fasso (To be published as SLAC RADIATION PHYSICS NOTE)

Question: Can OTR Screen be used in the LCLS undulator without causing significant radiation damage to the magnets?

Problem Setup and Initial FLUKA Simulations by A. Fasso (To be published as SLAC RADIATION PHYSICS NOTE)

Screen Material Diamond

Screen Thickness 100 microns

Screen Location 41 cm Upstream of 1st Und

Bunch Charge 1 nC

Bunch Repetition Rate 120 Hz

Electron Energy 13.64 GeV

Simulated Undulator Length 83 m



Longitudinal Distribution of Dose Deposited in Magnets (3) Longitudinal Distribution of Dose Deposited in Magnets (3)

Alberto FassòAlberto Fassò


Radiation Damage Measurements on NdFeBRadiation Damage Measurements on NdFeB

Change in Intrinsic Remnant Induction from Fast –Neutron Irradiation in 252Cf Spectrum[Fig 16 from J. Alderman, P.K. Job, R.C. Martin, C.M. Simmons, G.D. Owen, J. Puhl, “Radiation-Induced Demagnetization of Nd-Fe-B Permanent Magnets,” APS Report LS-290 (2000)]

Change in Intrinsic Remnant Induction from Fast –Neutron Irradiation in 252Cf Spectrum[Fig 16 from J. Alderman, P.K. Job, R.C. Martin, C.M. Simmons, G.D. Owen, J. Puhl, “Radiation-Induced Demagnetization of Nd-Fe-B Permanent Magnets,” APS Report LS-290 (2000)]

On-set of field change at 1014 n/cm2.

On-set of field change at 1014 n/cm2.

Fast-Neutron Fluence most likely source of damage.Fast-Neutron Fluence most likely source of damage.



Longitudinal and Vertical Distribution of Neutron Fluence (6a) Longitudinal and Vertical Distribution of Neutron Fluence (6a)

Alberto FassòAlberto Fassò

[cm] [cm]

[cm

]

[cm

]

Maximum at 1013 n/cm2/dayMaximum at 1013 n/cm2/day

n/cm2//dayn/cm2//dayn/cm2/electronn/cm2/electron



Damage clearly observed for neutron fluences of the order of 1014 n/cm2 byJ. Alderman, P.K. Job, R.C. Martin, C.M. Simmons, G.D. Owen, and J. Puhl, “Radiation-Induced Demagnetization of Nd-Fe-B Permanent Magnets,” APS Report LS-290 (2000)

Integrated levels of neutron fluences of 1014 n/cm2 would be reached after 10 days for 120 Hz, 1 nC, when keeping a 100 micron thick screen continuously inserted.

Integrated radiation doses can be strongly reduced under controlled operation at 10 Hz, .1 nC, with a 1-micron thick screen. This increases time to reach integrated fluence levels at continuous use to more than 300 years.

The planned occasional use of OTR screens should not present any problem.

Damage clearly observed for neutron fluences of the order of 1014 n/cm2 byJ. Alderman, P.K. Job, R.C. Martin, C.M. Simmons, G.D. Owen, and J. Puhl, “Radiation-Induced Demagnetization of Nd-Fe-B Permanent Magnets,” APS Report LS-290 (2000)

Integrated levels of neutron fluences of 1014 n/cm2 would be reached after 10 days for 120 Hz, 1 nC, when keeping a 100 micron thick screen continuously inserted.

Integrated radiation doses can be strongly reduced under controlled operation at 10 Hz, .1 nC, with a 1-micron thick screen. This increases time to reach integrated fluence levels at continuous use to more than 300 years.

The planned occasional use of OTR screens should not present any problem.


Conclusions

Break lengths structure simplified and finalizedAC conductivity risk can be mitigated.(Al, Oblong Cross-Section, Gain Tapering)Fine tuning of undulator tolerance budget is underway.Cradle component arrangement issues are being addressed.Mitigation for insufficient knowledge of earth field component inside undulator hall is under investigation.System for radiation damage calculations has been set up for FLUKA. Initial result look supportive for use of OTR screens.

Break lengths structure simplified and finalizedAC conductivity risk can be mitigated.(Al, Oblong Cross-Section, Gain Tapering)Fine tuning of undulator tolerance budget is underway.Cradle component arrangement issues are being addressed.Mitigation for insufficient knowledge of earth field component inside undulator hall is under investigation.System for radiation damage calculations has been set up for FLUKA. Initial result look supportive for use of OTR screens.


End of Presentation

Documents

Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting [email protected] Undulator Physics