Undulator Prototype Status and Plans

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					                            Undulator Prototype

                              Status and Plans

                                     Marion M. White APS-ASD


Argonne National Laboratory
                            A U.S. Department of Energy
                            Office of Science Laboratory
Office of Science
U.S. Department of Energy   Operated by The University of Chicago
Outline – Prototype Undulator Status

   • Design Challenges
   • Mechanical Design Features
   • Performance
   • Improvements
   • Canted Pole Undulator Measurements
   • Plans
   • Summary



                                                              2
  Pioneering                              Office of Science
  Science and                             U.S. Department
  Technology                                      of Energy
Undulator Design Parameters

   Parameter                   Specified Value
   Undulator Type              Planar Hybrid
   Magnet Material             NdFeB
   Pole Material               Vanadium Permendur
   Pole Gap (Min. Allowance) 6 mm
   Period Length             30 mm
   Effective Magnetic Field    1.296 Tesla
   Effective K Value           3.63
   Undulator Segment Length    3.40 m
   Nr. of Undulator Segments   33
                                                                   3
  Pioneering                                   Office of Science
  Science and                                  U.S. Department
  Technology                                           of Energy
LCLS – Familiar Design Challenges
 Between APS insertion devices and the LEUTL FEL,
 the APS team has a lot of undulator experience with:
          •     High-quality undulator magnetic fields
          •     Magnetic tuning for phase errors and trajectory
                straightness
          •     Variable and fixed gaps
          •     Phasing undulator ends
          •     Magnetic design
                 - NdFeB magnets
                 - Vanadium permendur poles
                 - 30-mm period
                 - K=3.63 so Beff=1.296 T                                   4
  Pioneering                                            Office of Science
  Science and                                           U.S. Department
  Technology                                                    of Energy
Magnetic Design

 Standard undulator design considerations:

                • Maximize the field
                • Don’t demagnetize the magnets
                • Don’t oversaturate the poles




                                                                      5
  Pioneering                                      Office of Science
  Science and                                     U.S. Department
  Technology                                              of Energy
Magnetic Design (2)

 Prevent Radiation Damage
       - Chose a new grade of magnet with higher
         coercivity (N39SH) for the prototype

       - Attention to minimizing the demagnetizing field

       - Design goal to be as restrictive as usual on the
         demagnetizing field, maybe even at the cost of
         higher pole saturation, then use the high Hc
         magnets

                                                                        6
  Pioneering                                        Office of Science
  Science and                                       U.S. Department
  Technology                                                of Energy
New Challenges – Uniformity and Stability

      Achieving a field-strength uniformity of 1.5 x 10-4
      along the undulator line is a challenge

            -   Gap change of 1.4 microns
            -   Vertical shift ~ 50 microns
            -   Temperature coefficient of the magnet is 0.1%/°C
            -   Thermal expansion

   And there may be a desire to taper in the future


                                                                              7
  Pioneering                                              Office of Science
  Science and                                             U.S. Department
  Technology                                                      of Energy
Outline – Prototype Undulator Status

   •      Design Challenges
   • Mechanical Design Features
   • Performance
   • Design Improvements
   • Canted Pole Measurements
   • Plans
   • Summary



                                                      8
  Pioneering                      Office of Science
  Science and                     U.S. Department
  Technology                              of Energy
Complete Undulator Module

      Quadrupole         Magnet Assembly      BPM




                Rails   CAM Movers         Cradle

                                                                    9
  Pioneering                                    Office of Science
  Science and                                   U.S. Department
  Technology                                            of Energy
              Mechanical Design




                                                  10
Pioneering                    Office of Science
Science and                   U.S. Department
Technology                            of Energy
Mechanical Design Features
                1. Housing is made from a forged Ti bar
                2. Ti was preferred over other materials
                   because:
                   •   Nonmagnetic
                   •   Low thermal expansion
                   •   Long-term stability
                   •   Rigidity to density ratio for minimal
                       deflection
                3. Al baseplate provides partial thermal
                   compensation
                4. Open on one side for magnetic
                   measurement access and shimming                       11
  Pioneering                                         Office of Science
  Science and                                        U.S. Department
  Technology                                                 of Energy
Titanium Strongback




                                          12
  Pioneering          Office of Science
  Science and         U.S. Department
  Technology                  of Energy
Mechanical design features, cont.




 Shims and push-pull      Magnetic side shims.
 screws adjust the gap.   Steel bars approach side
 Magnets are clamped      of pole. Correction up to
 from only one side.      ~3% in field.
                                                               13
  Pioneering                               Office of Science
  Science and                              U.S. Department
  Technology                                       of Energy
Pole clamping




Poles have titanium wings, and
are clamped on both sides




                                                     14
  Pioneering                     Office of Science
  Science and                    U.S. Department
  Technology                             of Energy
Pole simplification now under consideration


       Eliminate the wings
       and screw the pole
       in from the bottom.
        Still being refined;
         will be used in a
         segment of the
          prototype and
              reviewed.


                                                        15
  Pioneering                        Office of Science
  Science and                       U.S. Department
  Technology                                of Energy
End-phase adjusters in the prototype
                •Piezo translators on end sections
                allowed gap & field strength
                adjustment
                •Over the last seven periods only
                •Adjusted phasing between
                undulators
                •Can relax the requirement for
                constant Beff between undulators to
                7x10-4
                •Travel range 100 micron each jaw
                (200 microns in total gap). 100
                microns corresponds to 29°.                     16
  Pioneering                                Office of Science
  Science and                               U.S. Department
  Technology                                        of Energy
Eccentric cam movers




 Each cam is driven by a separate motor
 Adjustable in both transverse directions & in roll, pitch, & yaw
                                                                          17
  Pioneering                                          Office of Science
  Science and                                         U.S. Department
  Technology                                                  of Energy
Outline – Prototype Undulator Status

   •      Design Challenges
   •      Mechanical Design Features
   • Performance
   • Design Improvements
   • Canted Pole Measurements
   • Plans
   • Summary



                                                           18
  Pioneering                           Office of Science
  Science and                          U.S. Department
  Technology                                   of Energy
Assembly - Magnet Sorting


                                          Single Magnets
                                           Matched Pairs




 Magnets were sorted by strength (Total Moment), then the
 strongest and the weakest were matched together.
 Very important – saved lots of time since we found we
 could use this vendor’s measurements “as is” for sorting;
 not all vendors routinely make these measurements.                    19
  Pioneering                                       Office of Science
  Science and                                      U.S. Department
  Technology                                               of Energy
Assembly - pole sorting
 After magnet sorting, the main contributor to field errors
 was pole height variation.
 Tall and short poles were paired, and RMS deviation in gap
 was reduced from 6.3 to 2.4 microns
                                            After sorting:
 But this pairing
 neglected the
 contribution of the Al
 base plate thickness,
 and variation due to
 the attachment to the
 Ti. Final gap variation
 was ±50 microns.

 Note – Put tighter tolerances on the Al baseplate for production                20
  Pioneering                                                 Office of Science
  Science and                                                U.S. Department
  Technology                                                         of Energy
Magnetic Tuning




   Nonetheless, the device met the trajectory straightness
   requirement (±2 micron) without tuning.
   After tuning, the wiggle-averaged trajectory was within a
   range of about 0.5 microns.

                                                                        21
  Pioneering                                        Office of Science
  Science and                                       U.S. Department
  Technology                                                of Energy
Phase Error Tuning
 The calculated spontaneous emission amplitude needed
 tuning to raise it from 93% to over 99% of ideal.
 (The rms phase error decreased from 11.2° to 6.5°.)




                                                                       22
  Pioneering                                       Office of Science
  Science and                                      U.S. Department
  Technology                                               of Energy
Temperature Dependence




Care must be taken in the measurements to allow the
undulator sufficient thermal equilibration time
Also need to correct for temperature dependence of the Hall
probe: (DBeff/Beff)/DT = -5.5 x 10-4 /°C
                                                                      23
  Pioneering                                      Office of Science
  Science and                                     U.S. Department
  Technology                                              of Energy
Outline – Prototype Undulator Status

   •      Design Challenges
   •      Mechanical Design Features
   •      Performance
   • Post-Prototype Design Improvements
   • Canted Pole Measurements
   • Plans
   • Summary



                                                           24
  Pioneering                           Office of Science
  Science and                          U.S. Department
  Technology                                   of Energy
Post-prototype Considerations

•   End phase adjustments
     - Piezos long-term stability for this application is untested

•   Adjustment to final gap has not yet been done, but can
    do this with the cant anyway.

• Assume temperature dependence is handled by the
    conventional facilities specifications.



                                                                            25
    Pioneering                                          Office of Science
    Science and                                         U.S. Department
    Technology                                                  of Energy
Radiation Damage – Post-prototype
•      Had considered using SmCo magnets
        - Better radiation resistance
        - Smaller decrease in strength with temperature rise
        - But overall weaker strength and more brittle
        - Ruled out based on schedule – no time for R&D.
•      Instead, take advantage of APS radiation exposure and
       damage experience at the APS.
•      Provide dose limit guidance and information to SLAC to
       be used as input into the undulator protection system.
•      Do not operate LCLS under conditions likely to
       result in damage to the undulators.
                                                                          26
    Pioneering                                        Office of Science
    Science and                                       U.S. Department
    Technology                                                of Energy
Post-prototype, cont.
 • A comb shunt for adjusting the field strength was proposed
 • Initial tests look promising, but added design complexity;
       (remote capability - considerable added design complexity)
 •     Also a possibility for end phase correction only




                                                                          27
     Pioneering                                       Office of Science
     Science and                                      U.S. Department
     Technology                                               of Energy
Outline – Prototype Undulator Status

   • Design Challenges
   • Mechanical Design Features
   • Performance
   • Post-Prototype Design Improvements
   • Canted Pole Measurements
   • Plans
   • Summary



                                                              28
  Pioneering                              Office of Science
  Science and                             U.S. Department
  Technology                                      of Energy
Canting The Gap

   •      A scheme ( thanks to J. Pflueger) of canting the poles so
          that field strength varies with lateral (horizontal) position
          was very promising.

   •      A test section was “canted” and measured with excellent
          results. Canting was adopted into the baseline.




                                                                               29
  Pioneering                                               Office of Science
  Science and                                              U.S. Department
  Technology                                                       of Energy
Canted Cross-section (exaggerated)


     LCLS
 Undulator
     Cross-
Section with
  Wedged
    Shims


                                                         30
  Pioneering                         Office of Science
  Science and                        U.S. Department
  Technology                                 of Energy
Effective Magnetic Field




• Measured slope of 6.6 Gauss/mm agrees with calculations
     (~ 5.7 Gauss/mm for 3 mrad cant).
•    Alignment accuracy needed for DB/B ~ 1.5x10-4 ~ 2 Gauss -> 0.3 mm
                                                                                31
    Pioneering                                              Office of Science
    Science and                                             U.S. Department
    Technology                                                      of Energy
RMS Phase Error




• No significant dependency on X
• An RMS phase error of ~ 6.5 degree is an upper limit for
  near-perfect (~100%) performance.                                    32
  Pioneering                                       Office of Science
  Science and                                      U.S. Department
  Technology                                               of Energy
Horizontal Trajectory (averaged over period
length) at 14.1 GeV




• Trajectory vs. X well behaved and well within the tolerance
    requirement of 2 mm maximum walk-off from a straight line.
•   Operational range is ±1.2 mm for ±1.0°C temperature
    compensation.                                                       33
    Pioneering                                      Office of Science
    Science and                                     U.S. Department
    Technology                                              of Energy
Fringe Fields at X=65 and 100 mm




•    Fringe fields with new shims are close to earth field
     for X=100 mm. (Earth field contribution to trajectory
     shift has to be corrected.)                                       34
    Pioneering                                     Office of Science
    Science and                                    U.S. Department
    Technology                                             of Energy
Fine adjustment of effective magnetic field
(Isaac’s field-tuning procedure )
 1. Select spacers with thickness step ~ 15 µm to set the
    effective field in the range of ±30 Gauss (1 µm in gap
    corresponds to ~ 2 Gauss in field).
 2. Set spacer horizontal position to adjust the effective field to
    ~ ±6 Gauss (spacers are wedged with 3 mm/mm cant)
 3. Set horizontal position of the undulator as a whole so the
    effective field is in the range ±2 Gauss (DB/B ~ ±1.5x10-4)
    (This step saves time and provides better accuracy)
 4. The undulator horizontal position could be remotely
    controlled during operation to compensate for in-tunnel
    temperature variations (motion of ±1.2 mm for ±1°C
    needed). Such option is available, if quadrupoles are
    separated from undulator sections.
                                                                           35
  Pioneering                                           Office of Science
  Science and                                          U.S. Department
  Technology                                                   of Energy
Magnetic needles for alignment




• Only one needle is required for alignment in the X direction
• One more needle has to be added at Y=0 for alignment in the Y
  direction                                                                 36
  Pioneering                                            Office of Science
  Science and                                           U.S. Department
  Technology                                                    of Energy
Outline – Prototype Undulator Status

   • Design Challenges
   • Mechanical Design Features
   • Performance
   • Post-Prototype Design Improvements
   • Canted Pole Measurements
   • Plans
   • Summary



                                                              37
  Pioneering                              Office of Science
  Science and                             U.S. Department
  Technology                                      of Energy
Scope and Plans – Undulator Systems
 •    33 Precision magnetic arrays with canted poles
 •    33 Support/alignment systems including:
       - Cradle that supports the undulator, BPM, and
         quadrupole magnet.
       - Precision CAM movers and motors enabling
         positioning, alignment, and adjustment of the cradle.
       - Rail system to move the undulator, facilitating manual
         retraction of an undulator out of the beamline and
         precision reproducible re-insertion.
 •    7 Spare Undulator Modules
 •    1 Undulator Transport Device for Installation
                                                                          38
  Pioneering                                          Office of Science
  Science and                                         U.S. Department
  Technology                                                  of Energy
Plan – Undulators (1)

 •    To meet schedule and funding profiles, and to ensure
      that the Undulator Systems are complete by July
      2007, we plan to procure the following long-lead items
      as early as possible in FY05:
          - Precision-machined titanium strongbacks
          - NdFeB Magnet blocks
          - Vanadium Permendur Magnet poles
 •    The same APS undulator experts, who were relied
      upon for design, construction, and assessment of the
      prototype, will finalize procurement packages for the
      LL items, in accordance with our Advance
      Procurement Plans [APP].                              39
  Pioneering                                       Office of Science
  Science and                                      U.S. Department
  Technology                                               of Energy
Scope – Quadrupole Magnet Systems

   •      33 Quadrupole Magnet Systems - installed
           - Permanent Magnet Quadrupole
           - Support with Precision Translator [settable to 5 um;
             readout to 1um]

   •      5 Spare Magnet Systems

   •      Separate steering is not included



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  Pioneering                                             Office of Science
  Science and                                            U.S. Department
  Technology                                                     of Energy
Summary
•   A full-scale prototype undulator was constructed and
    tested at APS, and met LCLS performance goals.
•   A subsequent design improvement, that of introducing a 3-
    mrad cant in the pole gap, was implemented using wedged
    spacers between the aluminum base plates and the titanium
    core. It was successfully tested and the concept was adopted
    in the baseline.
•   A disadvantage of the canted-pole design is the necessity to
    provide a separate support for vacuum chamber
•   Magnetic measurements show good agreement with
    calculated change of the effective magnetic field versus X
    (horizontal motion).
•   No significant change of the RMS phase error versus X was
    measured.                                                    41
    Pioneering                                         Office of Science
    Science and                                        U.S. Department
    Technology                                                 of Energy
Current Status
• Significant effort has been devoted to planning, resulting in a detailed
    undulator construction schedule that is integrated with the BPM,
    quadrupole and vacuum chamber construction and testing. The
    undulator schedule and the magnet measurement schedule are mostly
    integrated, and are consistent with completion of undulator systems in
    July 2007.
•   A skeleton installation schedule exists; details are being added and
    integration with the rest of the schedule is ongoing.
•   Schedule refinement is ongoing.
•   Costs were estimated by in-house experts with relevant experience and
    were based on vendor quotes and previous experience. Cost scrubbing
    will continue.
•   The greatest schedule risks come from:
     - Design changes
     - Delayed funding
                                                                                   42
    Pioneering                                                 Office of Science
    Science and                                                U.S. Department
    Technology                                                         of Energy