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Undulator Physics Diagnostics Commissioning Strategy HeinzDieter Nuhn, SLAC SSRL August 11, 2004

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PRD 1.4-003 Beam Based Alignments System Requirements (http://www-ssrl.slac. ... Based Detection of Gain Reducing Errors. Using Spontaneous Radiation. Using FEL ... – PowerPoint PPT presentation

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Title: Undulator Physics Diagnostics Commissioning Strategy HeinzDieter Nuhn, SLAC SSRL August 11, 2004


1
Undulator Physics Diagnostics / Commissioning
Strategy Heinz-Dieter Nuhn, SLAC / SSRL August
11, 2004
  • Undulator Overview
  • FEL Parameters
  • Diagnostics and Commissioning Strategy

2
Linac Coherent Light Source
3
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4
Undulator Segment Prototype
5
Workshops and Meetings
  • Undulator Parameter Workshop
  • October 24, 2003, Argonne
  • URL http//www-ssrl.slac.stanford.edu/lcls/undula
    tor/meetings/2003-10-24_parameter_workshop/
  • Undulator Review
  • November 14, 2003, Argonne
  • URL http//www-ssrl.slac.stanford.edu/lcls/undula
    tor/meetings/2003-11-14_review/
  • Undulator Diagnostics and Commissioning Workshop
  • January 19-20, 2004, UCLA
  • URL http//www-ssrl.slac.stanford.edu/lcls/undula
    tor/meetings/2004-01-19_diagnostics_comissioning/
  • Report http//www-ssrl.slac.stanford.edu/lcls/wor
    kshops/2004-09-22_diag_comm/lcls-tn-04-2.pdf
  • Undulator Systems Review
  • March 3-4, 2004, Argonne
  • URL http//www-ssrl.slac.stanford.edu/lcls/undula
    tor/meetings/2004-03-03_review/
  • Undulator Physics and Engineering Meeting
  • June 28-29, 2004, Argonne
  • URL http//www-ssrl.slac.stanford.edu/lcls/undula
    tor/meetings/2004-06-28_phy_eng/
  • Undulator Meeting
  • July 23, 2004, Argonne
  • URL http//www-ssrl.slac.stanford.edu/lcls/undula
    tor/meetings/2004-07-23_und_mtg/

6
Undulator Design Changes Since May 2003
  • Canting of Undulator Poles
  • Remote Undulator Roll-Away and K Adjustment
    Function
  • Increase in Undulator Gap
  • Reduction in Maximum Beam Energy
  • Reduction in Quadrupole Gradient
  • Increase in Beta Function
  • Increase in Break Section Length

7
Amplitudes of Undulator Parameter Changes
  • May 2003 August 2004
  • Undulator Type planar hybrid
  • Magnet Material NdFeB
  • Wiggle Plane horizontal
  • Gap 6.0 6.8 mm
  • Gap Canting Angle 0.0 4.5 mrad
  • Period Length 30.0 0.1 mm
  • Effective On-Axis Field 1.325 1.249 T
  • Effective Undulator Parameter K 3.630 0.015
    3.500 0.015
  • Module Length 3.40 m
  • Number of Modules 33
  • Undulator Magnet Length 112.2 m
  • Standard Break Lengths 18.7 - 18.7 - 42.1 48.2 -
    48.2 - 94.9 cm
  • Total Device Length 121.0 131.9 m
  • Lattice Type FODO

8
Performance Impact of Changes (1.5 Å)
  • May 2003 August 2004 Change
  • Electron Beam Energy 14.35 13.64 GeV -5.0
  • Emittance 0.043 0.045 nm rad 5.2
  • Avg. Electron Beam Radius 27 35 µm 27.5
  • Avg. Electron Beam Divergence 1.6 1.3 µrad -17.5
  • Peak Beam Power 49 46 TW -5.0
  • FEL Parameter (3D) 0.00033 0.00032 -3.5
  • Power Gain Length (3D) 4.2 4.3 m 3.6
  • Saturation Length (w/o Breaks) 82 86 m 4.9
  • Saturation Length (w/ Breaks) 89 101 m 13.5
  • Peak Saturation Power 7.4 7.6 GW 2.5
  • Coherent Photons per Pulse 1.41012 1.51012 2.5
  • Peak Brightness 1.51033 1.51033 2.5
  • Average Brightness 4.61022 4.71022 2.5
  • Peak Spont. Power per Pulse 91 73 GW -19.7
  • Increase due to 3D effects (reduction in
    diffraction due to beam radius increase)
  • Ph./s/mm2/mr2/.1

9
Undulator Specification Documents
  • Controlled Specification Documents support
    Inter-Laboratory Communications
  • Global Requirements Document (GRD)
  • GRD 1.1-001 (http//www-ssrl.slac.stanford.edu/lcl
    s/prd/1.1-001-r1.pdf)
  • Physics Requirements Documents (PRDs)
  • PRD 1.4-001 General Undulator System Requirements
    (http//www-ssrl.slac.stanford.edu/lcls/prd/1.4-00
    1-r0.pdf)
  • PRD 1.4-002 Magnetic Measurement Facility
    Requirements (http//www-ssrl.slac.stanford.edu/lc
    ls/prd/1.4-002-r0.pdf)
  • PRD 1.4-003 Beam Based Alignments System
    Requirements (http//www-ssrl.slac.stanford.edu/lc
    ls/prd/1.4-003-r0.pdf)
  • PRD 1.1-314 LCLS Beam Position Measurement System
    Requirements (http//www-ssrl.slac.stanford.edu/lc
    ls/prd/1.1-314-r0.pdf)
  • Engineering Specification Documents (ESDs)
  • ESD 1.4-100 Undulator Segment Specifications
  • ESD 1.4-101 Undulator Segment Support
    Specifications
  • ESD 1.4-102 Quadrupole Magnet Specifications
  • ESD 1.4-103 Diagnostics System Specifications
  • ESD 1.4-104 Wire Position Monitor System
    Specifications
  • ESD 1.4-105 Hydrostatic Leveling System
    Specification
  • ESD 1.4-106 Vacuum System Specifications
  • ESD 1.4-106 Controls Specifications
  • Interface Control Documents (ICDs)
  • ICD 1.4-500 Undulator Mechanical Interfaces

10
FEL Commissioning Workshop 1/19-20/04
  • Scope
  • Commissioning of the FEL Undulator with Beam
  • Goals
  • End-Of-Construction Goal
  • Defined by DOE to close-off construction project
    (CD-4)
  • One of the first Commissioning Milestones
  • Commissioning Goal
  • Get LCLS ready for operation
  • Prerequisites
  • Undulator, Diagnostics, Shielding, Beam Dump etc.
    in Place
  • Commissioning Without Beam for all Components
    Complete
  • Main Commissioning Tasks
  • Characterization of Electron Beam Up-Stream of
    Undulator
  • Establishment of a Good Beam Trajectory Through
    Undulator to Beam-Dump
  • Characterization of Spontaneous Radiation
  • Establishment of SASE Gain
  • Characterization of FEL Radiation

Low Charge Single Shot
Low Charge, 10 Hz
10 Hz
11
Workshop Issues
  • Undulator Radiation Protection
  • Measurements of FEL Radiation vs. Z
  • Radiation Power Damage to Inter Undulator X-Ray
    Diagnostics
  • End-of-Undulator Diagnostics
  • Beam Based Detection of Gain Reducing Errors
  • Using Spontaneous Radiation
  • Using FEL Gain Curve
  • Numerical Simulation Support for Detector
    Development and Commissioning

12
Undulator Radiation Protection
Two-Phase, Two-Plane Collimation, 1½ Times
p/2
p/2
?3 mm
?2.5 mm
edge scattering
?2 mm
halo
e- beam
undulator beam pipe
x1
x2
x3
phase-1 again
phase-2
phase-1
(also collimation in y and energy see next
slides)
13
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14
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15
  • Track 100 times with
  • DL2 BPM rms res. 10 mm
  • DL2 BPM rms misa. 200 mm
  • DL2 Quad rms misa. 200 mm
  • Undulator Quad rms misa. 100 mm
  • Correct und-launch, then open stopper-2 for one
    beam shot…
  • Just 11 of 100 trajectories exceed ?2.5 mm within
    undulator
  • None exceed ?3.5 mm

G 110 T/m
First beam shot through undulator?
16
FEL Gain Measurement
  • Desirable measurements as function of position
    along undulator
  • Intensity (LG, Saturation)
  • Spectral Distribution
  • Bunching

Saturation
Exponential Gain Regime
Undulator Regime
1 of X-Ray Pulse
Electron Bunch Micro-Bunching
17
Dose / Power Considerations
Fluence to Melt
Energy Density Reduction of a Reflector
Be will melt at normal incidence at E lt 3 KeV
near undulator exit. Using Be as a grazing
incidence reflector may gain x 10 in tolerance.
18
End-of-Undulator Commissioning Diagnostics
  • Measurements
  • Total energy
  • Pulse length
  • Photon energy spectra
  • Spatial coherence
  • Spatial shape and centroid
  • Divergence

19
4' Muon shield
PPS
Access Shaft
PPS
Spectrometer, Total Energy
Solid Attenuator
Access Shaft
Direct Imager Indirect Imager
Slit A
Slit B
Windowless Ion Chamber
PPS
Gas Attenuator
13' Muon shield
Fast close valve
20
Measurement of SASE Gain along the undulator
  • Direct Detectors in the Breaks between Undulator
    Segments.
  • No good solution for x-ray detector in existence,
    yet.
  • Alternative End-Of-Undulator Diagnostics
  • Turn-Off Gain at Selectable Point Along Undulator
    by
  • Introduction of orbit distortion
  • Removal of undulator segments (New roll-away
    option)
  • Characterize x-ray beam at single station down
    stream of undulator

21
Measurement of SASE Gain with end-of-undulator
diagnostics
  • GENESIS Simulations by Z. Huang

22
Spontaneous vs. FEL Radiation -1-
23
Spontaneous vs. FEL Radiation -2-
24
Workshop Recommendations
  • No Intra-Undulator-Segment X-Ray Diagnostics in
    Baseline Design
  • Instead End-of-Undulator X-Ray Diagnostics to
    Characterize FEL Radiation vs. z
  • Trajectory Distortion Method
  • Roll-Away Undulator Segments Function
  • Investigation of Spontaneous Radiation as
    Diagnostics Tools
  • Code Development to Support Commissioning
  • Areas for Follow-Up RD
  • Study of Spectral and Spatial Distribution of
    Spontaneous Radiation
  • Diagnostics Prototyping
  • Microbunching Measurement

25
Conclusions
  • Requirements for LCLS undulator are well
    established
  • LCLS undulator performance requirements are well
    understood
  • Risks have been assessed and undulator
    specifications address the risk
  • Detailed commissioning strategy is being
    developed. Startup Test Plan exists.
  • PRD 1.1-002 LCLS Start-Up Test Plan
    (http//www-ssrl.slac.stanford.edu/lcls/prd/1.4100
    2-r1.pdf)

26
End of Presentation
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