Undulator Alignment Strategy Heinz-Dieter Nuhn, SLAC / LCLS April 20, 2006

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Undulator Alignment StrategyHeinz-Dieter Nuhn,
SLAC / LCLSApril 20, 2006

• Alignment Overview
• Alignment Tolerances
• Alignment Monitoring
• Correction Zones

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Undulator Alignment Overview

• The focus of the undulator alignment is on
• Quadrupoles and Beam Position Monitors (BPMs)
• Beam Finder Wires (BFW)
• Undulator Strongbacks (Segments)
• The alignment procedures include
• Girder Component Alignment checked on CMM
• Conventional Tunnel Alignment
• Beam Based Alignment (BBA) Energy Scan followed
  by BFW
• Continuous Monitoring and Correcting of Component
  Positions
• Auxiliary alignment procedures include
• Segment Fiducialization SUSA wrt. Segment
  fiducials
• Quadrupole Fiducialization Magnetic center wrt.
  Quad fiducials
• BFW Fiducialization Wire location wrt. BFW
  fiducials

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Main Alignment Concepts

• Pre-alignment (baselining) uses the manual
  adjustments on top of the support structures.
• Relative alignment of Girder components is
  achieved and maintained through common-girder
  mounting checked by CMM
• Girder-to-Girder alignment is (remotely)
  controlled based on cam-shaft technology
• During initial alignment with focus on
  quadrupole and BFW positions
• For quadrupole position control, i.e. beam
  steering during BBA
• For compensation of ground motion effects etc.
• Beam-Based-Alignment uses quadrupole magnets in
  two ways
• via off-center dipole fields. Change is done
  through cam-based girder motion, which will align
  all girder components to the beam. Minimum motion
  range covers area of circle with 700 µm radius
• via dipole trim-windings on Quadrupole Magnets
  (used for fine adjustments.) Range equivalent to
  100 µm of Quad motion

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Girder Components Summary

• Main girder components include
• Beam Finder Wire (BFW)
• Undulator strongback arrangement mounted on
  horizontal slides
• Vacuum chamber support
• BPM
• Quadrupole
• Mounts for the Wire Position Monitor (WPM) system
• Sensors of the Hydrostatic Leveling System (HLS)
• Diagnostics components
• The undulator strongback arrangement (Segment) is
  mountable on and removable from the girder with
  the vacuum chamber in place and without
  compromising the alignment of the vacuum chamber
• Segments will be taken off the girder for
  magnetic measurements
• Segments will be interchangeable without the need
  for the CMM
• The complete girder assembly will be aligned on
  the Coordinate Measurement Machine (CMM).

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Beam Finder Wire (BFW)
A misaligned undulator will not steer the beam.
It will just radiate at the wrong wavelength.The
BFW allows the misalignment to be detected. (also
allows beam size measurements)
Undulator
Quad
BFW
Beam Direction
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UndulatortoQuad FiducializationTolerance Budget
Individual contributions are added in quadrature
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UndulatortoBFW FiducializationTolerance Budget
Individual contributions are added in quadrature
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Alignment Tolerance Summary
Tolerances for Component Alignment on Girder Value Unit
Horizontal alignment of quadrupole and BPM to Segment (rms) 125 µm
Vertical alignment of quadrupole and BPM to Segment (rms) 60 µm
Horizontal alignment of BFW to Segment (rms) 100 µm
Vertical alignment of BFW to Segment (rms) 55 µm
Tolerances for Girder Alignment in Tunnel Value Unit
Initial rms uncorrelated x/y quadrupole alignment tolerance wrt straight line 100 µm
Initial rms correlated x/y quadrupole alignment tolerance wrt straight line 300 µm
Longitudinal Girder alignment tolerance 1 mm
Undulator Segment yaw tolerance (rms) 240 µrad
Undulator Segment pitch tolerance (rms) 80 µrad
Undulator Segment roll tolerance (rms) 1000 µrad
Component Monitoring and Control Tolerance Value Unit
Horizontal / Vertical Quadrupole and BPM Positions (Depending on Zone) ? 2 µm
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Survey Monuments
Extract from ESD 1.4-113 Undulator Tunnel Survey
Monument Positions B. Fuss
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Undulator Hall Network
Monuments
Tracker Positions
Quadruples
Level
Tracker
sdh 50 µm
sD 30 µm sh 30 µm / D sv 50 µm /D
Inputs
sz 22 µm sx 47 µm sy 46 µm
Results
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Undulator Alignment Controls

• Manual Adjustability
• Rough CAM position adjustability relative to
  fixed support.ranges x (12 mm) y (25 mm) z
  (12 mm)
• Quadrupole, BFW, BPM, Vacuum Chamber, and Segment
  adjustability to Girder. ranges x (gt1 mm) y
  (gt1 mm) z (gt1 mm)
• Remote Adjustability
• Girder x, y, pitch, yaw, roll ?1.5 mm x and y
• Enables alignment of all beamline components to
  the beam axis.
• Roll motion capability is to be used to keep roll
  constant
• Undulator x 80 mm range
• Provides control of undulator field on beam axis.
• Horizontal slide stages move undulator strongback
  independent of Girder and vacuum chamber.

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Undulator Segment Supports
Manual Adjustments
Horizontal Slides
Segment
Vacuum Chamber Support
Girder
Cam Movers
ManualAdjustments
Fixed Supports
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Undulator Alignment Monitoring Elements

• Hydrostatic Leveling System (HLS)
• Monitored Degrees of Freedom are y, pitch, and
  roll
• Wire Position Monitoring System (WPM)
• Monitored Degrees of Freedom are x, (y),
  (pitch), yaw, and roll
• Temperature Sensors
• In support of HLS/WPM readout corrections,
  undulator K corrections, and component motion
  interpretation.
• Beam Position Monitors
• Monitored quantities are x and y position of
  electron beam
• Quadrupoles
• Monitored quantities are electron beam x and y
  offset from quad center

Transverse Locations Tracked by HLS and WPM
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Component Position Monitoring Systems(Alignment
Diagnostics System ADS)
Wire Position Monitor system (WPM)

• Resolution lt 100 nm in X Y direction
• Instrument Drift lt 100 nm per day
• Moving Range 1.5 mm in X Y direction
• Accuracy 0.1 of full Scale
• Availability Permanent, no interrupts

X and Y, can be measuredRoll, Jaw Pitch can be
calculated.
Hydrostatic Leveling System (HLS)
Capacitive Sensor

• Precision lt 1 mm
• Instrument Drift 1-2 mm / month
• Accuracy lt 0.1 of full Scale

Roll
Y
Ultrasound Sensor

• Precision lt 0.1 mm
• Instrument Drift potentially no drift
• Accuracy lt 0.1 of full Scale

Pitch
Y, can be measuredRoll Pitch can be
calculated.
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ADSCommon Sensor Support
Quadrupole X Y- Position will be measured
relative to the references. Roll, Pitch, Yaw and
Torsion of the Girder can be calculated.
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Strategies for Controlling Component Motion

• Girder motion will be caused by
• Ground Motion
• Temperature Changes
• CAM Rotation
• Girder motion will be monitored in 2 ways.
• Directly, through the Alignment Diagnostics
  System
• Indirectly, through impact on electron beam
  trajectory (as detected by BPMs)
• Girder Positions will be frequently corrected
  using the CAM movers.

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Correction Zones

• Zone 1 (non-invasive correction)
• 120-Hz traj-feedback (LTU BPMs)
• 0.1-Hz traj-feedback (und. BPMs)
• Zone 2 (Dt gt 1 hr, ?P/P0? gt 90, non-invasive)
• Maintain component alignment based on ADS

mo

• Zone 3 (Dt gt 24 hr, ?P/P0? gt 90, non-invasive)
• Maintain component alignment based on ADS
• Possible x-ray pointing correction
• Zone 4 (Dt gt 1 mo, ?P/P0? gt 75, machine time)
• One iteration of BBA (lt1 hr)
• Zone 5 (Dt gt 6 mo, shut-down)
• Reset movers set to zero and manual realignment
  (1 wk)
• Full 3 iterations of BBA (3 hrs)

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Alignment Function Diagram
Undulator Hall
MMF
USE OF DIAGNOSTICS COMPONENTS
Segment Tuning and Fiducialization
Supports Alignment
Quadrupole Fiducialization
Environmental Field Measurement
BFW Fiducialization
Girder Pre- Alignment
Component Alignment on Girder
ADS Installation
ADS(HLS/WPM)
Undulator Segment Installation
Girder Alignment using ADS
BPMs
Quads
Electron Beam-Based Alignment
Segment Tuning
Loose End-Alignment
BFWs
Continuous Position Correction
Every 2 4 weeks Invasive Correction
Once per month Swap 3 Segments
Once every 6 month Re-baselining
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Conclusions

• The X-ray-FEL puts very tight tolerances on
  magnetic field quality, electron beam
  straightness, and Segment alignment.
• These tolerances can be achieved through Beam
  Based Alignment (BBA) procedures based on BPMs
  and Quadrupoles (with energy scan) as well as
  BFWs.
• Relative component alignment to required
  tolerances will be achieved through common girder
  mounting.
• Main tasks of the conventional alignment and
  motion systems are
• Component fiducialization and alignment on girder
  
• Conventional alignment of girders in Undulator
  Hall as prerequisite for BBA
• The Alignment Diagnostic System measures and
  enables the correction of girder movement due to
  ground motion, temperature changes, and CAM mover
  changes.
• A strategy is in place for using the monitor
  systems and controls to establish and maintain a
  straight trajectory.

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End of Presentation