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NSLS II Metrology R&D Activities

Peter Z. Takacs

Experimental Facilities Advisory Committee Review20 Oct 2006

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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, 1980sBNL developed the metrology to force manufacturers to improve their

fabrication processes: surface roughness, then slope errorWe need to do it again.

Soft X-ray Beam Lines: 1-sigma actual performance and predicted for 0.5µrad errorUndulator/Wiggler NSLS X25 NSLS X29 APS UA NSLS-II

Energy resolution w/ Si(111 ) (eV) 12 4 1.8 1.8Vertical focus size, FWHM (µm) 200 100 30 11.9Horizontal focus size, FWHM (µm) 700 250 60 28.5

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

RMS mirror figure error [µrad] 0.0 0.1 0.5 1.0 2.0

Vertical focus size, FWHM (µm) 1.02.4

2.66.1

11.828.3

23.556.5

47.0112.8

Horizontal focus size, FWHM (µm)15.533.6

15.834.2

21.045.4

32.269.7

58.5126.7

Monochromatic intensity at 12 k eV(ph/sec/µm2)

1.0x1013

2.0x10124.5x1012

8.6x10117.9x1011

1.5x10112.7x1011

5.5x10107.7x1010

1.5x1010

Where are mirrors in NSLS II beamlines?

X-ray scattering/crystallography - KB mirrors, bendableSmall-angle x-ray scattering (SAXS) - KB primary pair and KB secondary pair,

both bendableScanning 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.

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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

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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

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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

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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, 063708 (2005)

View from interferometerin stitching of Osaka

elliptical cylinder

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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 MachiningY. Mori, Osaka

High speed rotating tool

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3. MRF polishing evaluationNeed 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 timeEstablish collaboration with QED

1. Produce super-polished Si flat2. Produce KB elliptical cylinders3. 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

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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.