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Shield and Fold Mirror DimensionsShield and Fold Mirror Dimensions

Michael Sholl

3 February 2005

MODIFIED by Robin Lafever

23 Feb 2005

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CautionCaution

• Final dimensions will live in configuration controlled drawings of shield and mirrors

• Purpose of this presentation is to provide starting point for mechanical designs

• Tom Diehl (FNAL) is in charge of final shield thickness• Stray light/optics controls inner and outer light path clearance of shield

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Area of InterestArea of Interest

• Area is tightly packed

• ~3mm clearance between shield and FM minimum

• Because focal plane array is rotated 45deg, sharp edge may be cut back before coating and polishing mirrror

• ROF requires fiber feed and clearance

• Shield pulled back 20mm from corner of extreme detector

• Stray light from incoming starlight does not reach inner shield wall, due to Cassegrain baffle

• Stray light reflected off detector, scattered off Z302 coated wall expected to be <0.001photons/s/pixel worst case (8th magnitude star)

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DimensionsDimensions

GLOBAL 0,0,0

4Ø86 (INNER EDGE)

688

FOCALSURFACE

800

6

1

Ø618

275

261

312

200

149

40 EXTERIOR PERIMETERSHIFT

MAJOR DIAMETEROF SMALL HOLE

MAJOR DIAMETEROF LARGE HOLE

LARGE HOLESHIFT

GLOBAL 0,0,0

FM CANTED AT 45° ANGLE

(THRU HOLES ARE ELLIPSESMINOR DIAMETERS ARE

COS(45°) MAJOR DIAMETER)

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DimensionsDimensions

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Diamond patternDiamond pattern

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Square patternSquare pattern

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Backward Raytrace to FMBackward Raytrace to FM

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Concept 1: Right-angle bendConcept 1: Right-angle bend

• Modular, removable ROF, attached with M3 fasteners

• Opposite end of ROF illuminated

• Ball lens reduces divergence of fiber output

• Right-angle mirror

• Cylindrical lens concentrates light on Spectralon surface

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Concept 2: Lower surface whiteConcept 2: Lower surface white

• Modular, removable ROF, attached with M3 fasteners

• Near end of ROF illuminated by nearby fiber

• Spectralon surface parallel to focal plane

• Cylindrical lens concentrates light on ROF

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Will this fit?Will this fit?

• Cyan surface is ROF location

• Clearance exists

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ConclusionsConclusions

• Use these dimensions as starting point for mechanical design• Final dimensions will live in machine drawings of parts• The internal iris, focal surface and FM clear aperture are defined in 00008-

MW02 (Telescope Specification)• Space exists for removable ROF designs• Tom Diehl has final word on shield thickness