Xray Reflection Gratings: Shaping, Metrology, Assembly

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X-ray Reflection GratingsShaping, Metrology,
Assembly

• Craig R. Forest, Matthew J. Spenko, Yanxia Sun,
  Alexander H. Slocum, Ralf K. Heilmann, Mark L.
  Schattenburg
• Space Nanotechnology LaboratoryMIT Center for
  Space Research
• Dan Golini
• QED Technologies, Inc.Rochester, NY
• Constellation X-Ray Mission Facility Science Team
  Meeting
• Cambridge, Massachusetts
• September 18-19, 2002

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Outline

• Grating implementation and design
• Shaping
• Magneto-rheologic fluid polishing (MRF)
• Surface metrology
• Shack-Hartmann system
• Assembly Truss

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Wolter telescope reflection grating optics
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X-ray reflection grating geometry(in-plane
diffraction)
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Principle of magneto-rheologic polishing
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Wafer polishing results with MRF
Bow Warp
rms microroughness
Before - 6.55 mm After - 0.81 mm
Before 0.66 nm After 0.64 nm
Material Silicon Diameter 100 mm
Thickness 0.45 mm
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Shack-Hartmann metrology tool
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Shack-Hartmann concept
Tradeoffs
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Design considerations

• Spectral
• Filtering

Source irradiance Spectral filter
transmittance Glass optical properties
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Performance evaluation
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Application

• Will meet SNL foil surface metrology needs for gt3
  years

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Assembly functional requirements

• Align gratings to within 1 µm of ideal
• Repeatably
• Same grating position between 2 different modules
• Accurately
• 2 foil positions within same flight module
• Integrate flight module

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Assembly strategy
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Assembly Truss
Flight Module
Lid
Flexure Bearings
Micrometers
Microcombs
Base
Reference Flat
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Comb actuation

• Need to move combs until they touch the reference
  flat
• Hertz contact stresses detectable
• 0.1µm actuation capability
• No hysteresis motion

Spring Microcombs
Reference Microcombs
Micrometers
Flexure Bearings
Force Sensors
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Optic alignment testing

• Optic angle measurement
• Autocollimator
• 0.1µrad resolution

Contact!
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Precision assembly
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• end

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Keplerian Design