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NSLS II Metrology R&D Activities. Peter Z. Takacs Experimental Facilities Advisory Committee Review 20 Oct 2006. Rationale for Metrology R&D for NSLS II. Every new advance in SR source design has driven improvements in optical components:

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Nsls ii metrology r d activities

NSLS II Metrology R&D Activities

Peter Z. Takacs

Experimental Facilities Advisory Committee Review

20 Oct 2006


Rationale for metrology r d for nsls ii
Rationale for Metrology R&D for NSLS II

  • Every new advance in SR source design has driven improvements in optical components:

  • Pre-NSLS (<1980) SR mirror slope error quality: >2 arc sec (10µrad)

  • Original NSLS mirror specs: 1 arc sec (5µrad) for <10µm spot size.

    • This was difficult for manufacturers to achieve

  • NSLS upgrade: 1 µrad for <1µm spot size.

    • This is now routine

  • NSLS II requirements are now 100 nrad (!)

  • “If you can’t measure it, I can make it.” - Norm Brown, LLNL, 1980s

  • BNL developed the metrology to force manufacturers to improve their fabrication processes: surface roughness, then slope error

  • We need to do it again.


  • Where are mirrors in nsls ii beamlines
    Where are mirrors in NSLS II beamlines?

    • X-ray scattering/crystallography - KB mirrors, bendable

    • Small-angle x-ray scattering (SAXS) - KB primary pair and KB secondary pair, both bendable

    • Scanning transmission x-ray microscope (STXM) - spherical grating monochromator (SGM) and steering mirrors for beam line branches.

    • High resolution inelastic x-ray scattering (IXS) beam line - spherical collimating mirror after pre-mono and KB pair after the high-res mono.

    • Superconducting wiggler - vertical focusing mirror for 50-100keV photons.

    • Soft x-ray beam lines - collimating and focusing optics

      Gratings, spheres, cylinders, paraboloids, ellipsoids, etc.

    Add “real world” slope error to soft x-ray beamline KB mirror surface:


    Challenges in nsls ii mirror development
    Challenges in NSLS II mirror development

    • Need to develop reliable source(s) of nm-quality mirror components.

      • Work with vendors to insure required mirror parameters are met.

      • Provide metrology feedback

    • Need to develop in-house metrology instrumentation and techniques adequate for nm figure and 100nrad slope errors.

    • Plan for mirror metrology R&D -- near-term and longer-term tasks:

      • Develop Next-Generation Long Trace Profiler for reliable 100nrad measurements.

      • Develop stitching interferometry system for high-resolution figure over complete 2D surface area of mirror.

      • Evaluate new polishing techniques

        • QED MagnetoRheological Finishing (MRF)

      • Develop in-situ LTP for beam line diagnostics

      • At-wavelength testing capability


    1 next generation ltp
    1. Next Generation LTP

    • Present LTP III limited by systematic errors at the 1-2 µrad level.

    • Need to improve internal optical components and air bearing stage.

      • Glass quality affects measurement accuracy

        • Replace commercial PBS with custom PBS - $5K to $20K estimates

      • Replace Al beam (100µrad err) with ceramic beam (<5µrad err)

      • New linear motor drive system

      • 2D camera

    • Explore high resolution LTP options for spatial periods <1mm

    BNL LTP III measuring Si cylinder


    Ng ltp resources required
    NG-LTP: Resources required

    • Zygo Wavelength-shifting PMI required for internal glass quality measurement.

      • New technique allows separation of front and back surface from interior

    • NewView Micro-PMI (or equivalent) required for surface roughness control of internal LTP components.

      • Essential for replacement of defunct MicroMap profiler (vintage 1985)

      • Also use for profilometry of mirrors and quantitative topography of nanostructures, e.g. refractive kinoform optics

    • Also requires software development to add 2D camera and speed data acquisition.

    • Collaboration with LBL

      • Software development

      • Quantity discount in custom optics procurement


    2 stitching metrology development
    2. Stitching metrology development

    QED SSI uses conventional Zygo Fizeau interferometer head combined with 6-axis positioning manipulator.

    Measured and predicted 40nm image shape from SSI on 100mm long elliptical cylinder.

    Yumoto,et al., RSI 76, 063708 (2005)

    • Subaperture stitching interferometry (SSI) necessary for 2D surface map

      • Required for deterministic surface info at ~50µm spatial periods

    • QED has the SSI metrology - companion to MRF machine.

      QED-developed algorithm solves for test surface error AND reference optics errors => self-calibrating, < 2nm residual errors.

    • Combine high resolution Fizeau PMI with LTP optical head.

    • Estimate 3 years to develop operational stitching system.

    View from interferometer

    in stitching of Osaka elliptical cylinder


    3 polishing r d
    3. Polishing R&D

    Elastic Emission Machining

    Y. Mori, Osaka

    • Lessons from Osaka:

      • EEM technology 20 years in development

      • EEM can produce nm-level figure accuracy

      • Requires novel metrology techniques

      • Not (yet) available commercially.

    • BNL will NOT go into fabrication business.

      • We must rely on commercial optical fabricators

    • Need to explore new polishing technologies to achieve 100nrad optics

    • Need for in-house metrology instrumentation

      • Replacement needed ASAP for defunct MicroMap (former NCP-1000) for surface roughness measurement

    • Magnetorheological finishing (MRF) is most promising new technique for SR optics

      • Developed by QED Technologies, Rochester

    High speed rotating tool


    3 mrf polishing evaluation
    3. MRF polishing evaluation

    • Need to demonstrate Angstrom-level surface finish capability of MRF process.

      • Basic process limitations? uses diamond grit

      • Need to fine-tune machine parameters: slurry chemistry, dwell time

    • Establish collaboration with QED

      • Produce super-polished Si flat

      • Produce KB elliptical cylinders

      • Develop SSI metrology for non-rot symmetry parts

    • We will evaluate surface quality in lab and performance in NSLS and/or APS beam line.

      • Use NewView surface profiler and NG-LTP.

      • Requires stitching metrology software development for rectangular substrate shape.

    • Successful results => transfer technolgy to MRF-capable vendor.

      • Zeiss has expressed interest in meeting our needs

        • Heavily invested in MRF machines


    Long term metrology tasks
    Long-term metrology tasks

    • 4. In-situ LTP

      • In-situ LTP needed for beam line diagnostics.

        • Measure thermal and mechanical distortion on high heat load optics.

        • Look for transient heating effects on rigid body alignment.

        • Locate beam footprint on optical surface for alignment check.

      • Need to design essential interface ports into mirror chambers.

        • View through window normal to surface

        • Use scanning penta prism inside chamber

    • 5. At-wavelength metrology

      • Develop phase retrieval image evaluation system for x-ray wavelengths.

        • Similar to Souvorov technique at SPring8

      • Useful for evaluating wavefront quality of various microfocusing optics

        • Zone plates, refractive optics, Bragg-Fresnel

      • Potential collaboration with J. Fienup at Rochester

        • Postdoc will be available in ~2yrs

      • Requires wavelength converter and camera hardware, software development

      • Test beam line would be useful for this and other at-wavelength methods.


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