1 BROOKHAVEN SCIENCE ASSOCIATES NSLS II Metrology R&D Activities Peter Z. Takacs Experimental Facilities Advisory Committee Review 20 Oct 2006

2 BROOKHAVEN SCIENCE ASSOCIATES Rationale for Metrology R&D for NSLS II Every new advance in SR source design has driven improvements in optical components: Pre-NSLS ( 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.

3 BROOKHAVEN SCIENCE ASSOCIATES Add “real world” slope error to soft x- ray beamline KB mirror surface: 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 keV photons. Soft x-ray beam lines - collimating and focusing optics Gratings, spheres, cylinders, paraboloids, ellipsoids, etc.

4 BROOKHAVEN SCIENCE ASSOCIATES 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: 1.Develop Next-Generation Long Trace Profiler for reliable 100nrad measurements. 2.Develop stitching interferometry system for high-resolution figure over complete 2D surface area of mirror. 3.Evaluate new polishing techniques  QED MagnetoRheological Finishing (MRF) 4.Develop in-situ LTP for beam line diagnostics 5.At-wavelength testing capability

5 BROOKHAVEN SCIENCE ASSOCIATES 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

6 BROOKHAVEN SCIENCE ASSOCIATES 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

7 BROOKHAVEN SCIENCE ASSOCIATES 2. Stitching metrology development 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. 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, (2005) View from interferometer in stitching of Osaka elliptical cylinder

8 BROOKHAVEN SCIENCE ASSOCIATES 3. Polishing R&D 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 Elastic Emission Machining Y. Mori, Osaka High speed rotating tool

9 BROOKHAVEN SCIENCE ASSOCIATES 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 1.Produce super-polished Si flat 2.Produce KB elliptical cylinders 3.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

10 BROOKHAVEN SCIENCE ASSOCIATES 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.