Transcript Undulator Physics Requirements and Alignment

Undulator Physics Requirements
and Alignment
Heinz-Dieter Nuhn, SLAC / LCLS
April 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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Undulator Break Lengths
Old Strategy
Characteristic Lengths
Length of Undulator Strongback (Segment):
Lseg = 3.4 m
Distance for 113 x 2p Phase Slippage:
L0 = 3.668 m
Distance for 2p Phase Slippage in Field Free Space:
Linc = lu (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-Pattern
2 – 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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Undulator Break Lengths
GINGER 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.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Undulator Break Lengths
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.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Fawley
Heinz-DieterWilliam
Nuhn, SLAC
/ LCLS
[email protected]
Undulator Break Lengths
GENESIS Simulations Time Domain Results
GENESIS results comparable to those from GINGER.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Reiche
Heinz-Dieter Sven
Nuhn, SLAC
/ LCLS
[email protected]
Undulator Break Lengths
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.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Fawley
Heinz-DieterWilliam
Nuhn, SLAC
/ LCLS
[email protected]
Undulator Break Lengths
(Old Strategy) New Strategy
Characteristic Lengths
Length of Undulator Strongback (Segment):
Lseg = 3.4 m
Distance for 113 x 2p Phase Slippage:
L0 = (3.668 m) 3.656 m
Distance for 2p Phase Slippage in Field Free Space:
Linc = lu (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-Pattern
2 – 2 – 4 ([0.482 m – 0.482 m – 0.910 m]) [0.470 m – 0.470 m – 0.898 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) 131.52 m
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Mitigation 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)
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Revisiting the Undulator Tolerance Budget
Separate budgets exist for undulator tolerances
Undulator Field Tuning
Segment Alignment
BBA
Floor Stability
A Monte Carlo model is being developed which
simultaneously includes all of the above errors
Calculates the cumulative phase error with MC statistics
Shows 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?
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
JimSLAC
Welch
Heinz-Dieter Nuhn,
/ LCLS
[email protected]
Undulator 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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Cradle Component Arrangement and Alignment
Problem 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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Cradle Component Arrangement and Alignment
Problem Description
BBA will only correct alignment of quadrupoles.
Undulator segment alignment is not affected.
Additional alignment strategy needed.
Horizonal
Before BBA
Quad
After BBA
Vertical
Before BBA
After BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Cradle Component Arrangement and Alignment
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.
Horizonal
Before BBA
Quad
After BBA
Vertical
Before BBA
After BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Cradle Component Arrangement and Alignment
Solution 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.
Horizonal
Monitor
Before BBA
Quad
After BBA
Vertical
Before BBA
After BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Cradle Component Arrangement and Alignment
Winning 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.
Horizonal
Quad BPM
Before BBA
Beam
Monitor
After BBA
Vertical
Before BBA
After BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Cradle Component Arrangement and Alignment
Undulator – to – Quad 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
5
10
Alignment Quadrupole to Undulator
40
40
Grand Total
65
70
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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter
Nuhn,
SLAC / LCLS
See R. Ruland
Talk for
discussion
[email protected]
Earth Magnetic Field Compensation
Strategy
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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Earth Magnetic Field Compensation
Schedule 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.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Earth Magnetic Field Effect on Trajectory
0.1-Gauss Earth’s field in x-direction – perfect system, quads on, no steering
0.1-Gauss Earth’s field in x-direction – perfect system, after BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Paul
Emma
Heinz-Dieter Nuhn,
SLAC
/ LCLS
[email protected]
Earth Magnetic Field Effect on Trajectory
0.1-Gauss Earth’s field in x-direction – standard errors, after BBA
no Earth’s field – standard errors, after BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Paul
Emma
Heinz-Dieter Nuhn,
SLAC
/ LCLS
[email protected]
Earth Magnetic Field Effect on Trajectory
0.2-Gauss Earth’s field in x-direction – standard errors, after BBA
0.1-Gauss Earth’s field in x-direction – standard errors, after BBA
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Paul
Emma
Heinz-Dieter Nuhn,
SLAC
/ LCLS
[email protected]
Earth Magnetic Field Compensation
Adjustable 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])
Quad BPM
Undulator
Quad BPM
Undulator
Quad BPM
Trajectory w/o Shim
Shim Position
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Trajectory w/ Shim
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Radiation Damage Calculations
from 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)
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
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Radiation Damage Calculations
from Inserted Screen
Longitudinal Distribution of Dose Deposited in Magnets (3)
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Alberto
Fassò
Heinz-Dieter Nuhn,
SLAC
/ LCLS
[email protected]
Radiation Damage Measurements on NdFeB
Fast-Neutron Fluence most likely source of damage.
On-set of field
change at
1014 n/cm2.
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)]
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Radiation Damage Calculations
from Inserted Screen
[cm]
[cm]
Longitudinal and Vertical Distribution of Neutron Fluence (6a)
[cm]
[cm]
n/cm2/electron
n/cm2//day
Maximum at
1013 n/cm2/day
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Alberto
Fassò
Heinz-Dieter Nuhn,
SLAC
/ LCLS
[email protected]
Radiation Damage Calculations
from Inserted Screen
Damage clearly observed for neutron fluences of the order of 1014 n/cm2 by
J. 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.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
Conclusions
Break lengths structure simplified and finalized
AC 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.
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]
End of Presentation
Undulator Physics Requirements April 7, 2005
Facility Advisory Committee Meeting
Heinz-Dieter Nuhn, SLAC / LCLS
[email protected]