Mechanical Design - PowerPoint PPT Presentation

Loading...

PPT – Mechanical Design PowerPoint presentation | free to view - id: aec11-YmZjN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Mechanical Design

Description:

The camera lens tube confines the stray light near the detector. ... Camera forward reflections. 2% from 2 last lenses. Research School of Astronomy & Astrophysics ... – PowerPoint PPT presentation

Number of Views:58
Avg rating:3.0/5.0
Slides: 35
Provided by: PeterMc150
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Mechanical Design


1
Mechanical Design
2
Mechanical Design Status
  • Mechanical design for Concentric V3 optical
    system began early January. First pass layout now
    complete.
  • Mechanisms design has been considered.
  • Just three more IGES models would help complete
    the design.

3
Spectrograph on the CWS Plate
4
NIFS Cross Section
5
Spectrograph Plan View
6
Spectrograph Assembly
Optical components distributed over CWS plate on
cantilevered support structures in a single
layer. Spectrograph is easy to maintain, some
focussing and servicing can be done in
integration frame.
7
  • Pick-Off Probe
  • Probe 10mm thick, drilled for NIFS and OIWFS test
    projector
  • Probe closely coupled to CWS. Does not touch
    baffle.

8
Pick-Off Probe
  • Probe 10 mm thick, drilled for science field and
    OIWFS test projector.
  • Probe closely coupled to CWS plate, but does not
    touch OIWFS baffle.

9
Pick-Of Probe Flexure Analysis
  • Probe flexure is very small.

10
  • Pick-Off Probe
  • Nearest guide star to science object 12.7
  • Scatter inside probe from bright stars in field.

11
OIWFS Guide Star Field
  • Guide stars to 12.7 ? from science object.
  • Bright stars may scatter into probe.

12
Pick-Off Probe Scatter Analysis
13
  • Input Optics
  • Cold Stop and sink
  • Direct rays under f256 converter. These bypass
    cold stop but do not reach slicer.

14
Spectrograph Input Optics
15
Focal Plane Mask Wheel
  • Twelve position wheel.
  • Position repeatability about 30 ?m.
  • Miniature version of NIRI Geneva drive and cam
    lock.

16
Spectrograph Input Optics Issues
  • How effective is the cold stop?
  • Can stray light be baffled?
  • Direct rays can pass under the focal ratio
    converter.
  • Bypass cold stop but do not reach image slicer.
  • lt 4 mm diameter footprint on filter.

17
  • IFU Image Slicer
  • Pinned or staircase assembly
  • Angular accuracy 30µrad Step 57µm. Accuracy
    -0.8µm per step.

18
Staircase Image Slicer
Manufacture position
Operation position
19
Staircase Image Slicer Mount
  • Angular accuracy 30 ?rad gt 57?0.8 ?m step.

20
Large Pinned Image Slicer
  • 120?50?1 mm slices.
  • 12 mm dowel pins.
  • 15 mm thick anvils.

21
Image Slicer Issues
  • Manufacture of image slicer elements.
  • Alignment of image slicer elements.
  • Alignment of IFU1 mount.
  • Stability under cool-down.
  • Flexure of IFU1 mount.

22
Mirror Array Manufacture
23
  • Pupil Mirror Generation.
  • Needs x,y,z, Diamond Turning machine.
  • No steps between mirrors.
  • 0.76mm diamond tip radius.

24
  • IFU-2 Support.
  • Crowded region.
  • Triple Fold Mirror.
  • Field and Pupil mirror arrays span beam.

25
IFU-2 Mount
  • Holds adjustable pupil and field mirror arrays.
  • Holds fixed triple fold mirror.
  • Crowded region requiring careful baffling.
  • Pupil and field mirror arrays span the beam.

26
IFU-2 Mount
27
Plan view on IFU
28
Collimator Mirror Mount
  • Largest optical component (160?70 mm).
  • Diamond turned 6061 aluminum.

29
Collimator Mirror Mount
30
Collimator Corrector Mount
  • Coarse X-Y adjustment only.
  • Non-circular shape.
  • Held in compliant mount like NIRI lens mount.

31
  • Grating Wheel
  • Seven gratings plus mirror in wheel.
  • Bearing and lock mechanism need 3µrad stability
    to meet Gemini specification.

32
Spectrograph Grating Wheel
  • Heaviest mechanism ( 4.9 Kg).
  • Seven gratings plus one mirror.
  • Bearing and lock mechanism require 3 ?rad
    stability to meet Gemini flexure specification.
  • Mounting
  • Preloaded, deep groove, ball bearings.
  • Vacuum-sputtered MDS lubricant.
  • Careful bearing design.

33
Spectrograph Grating Mounts
  • Gratings held on adjustable three-point mounts.
  • Cooled via straps to grating wheel.

34
Spectrograph Camera Lens Mount
  • Lenses mounted in aluminum tube with zero
    clearance when cold.
  • Lens tube held on brackets from CWS plate.
  • Tongue and groove system maintains alignment to
    detector.

35
  • Flat Ribbon Cable
  • Run direct from hermetic connector to detector
    circuit card without twisting.

36
Detector Mounting
  • No remotely controlled detector focussing
    mechanism will be used.
  • Detector in light-tight box.
  • Detector pressed against a ceramic ring aligned
    to focal plane.
  • Rigid circuit card.
  • Short lead length to controller.

37
Detector Circuit Board
  • Dual flex-circuit from hermetic connector to
    circuit board.

38
Baffling Design
39
Baffling Issues
  • The biggest sources of stray light are the
    detector ( 30) and the grating ( 20).
  • The camera lens tube confines the stray light
    near the detector.
  • The detector views a large solid angle to the
    camera tube.
  • The gratings can not see directly out to the sky
    or telescope past the IFU and cold stop.

40
Baffling
  • Sheet metal baffles coated with Aeroglaze.
  • Sheet metal baffles cover both motors.
  • Plate baffles inside camera mounting tube.

41
Baffling Philosophy
42
Baffling Construction
  • Sheet metal baffling.
  • Light, simple, with sharp edges.
  • Coat with Aeroglaze or similar IR black.

43
Spectrograph Housing
  • 8 mm thick, cast, light-tight box will enclose
    spectrograph.
  • Air vent in cover.
  • Labyrinths to pass wiring.
  • Spectrograph radiation shields as for NIRI.

44
Spectrograph Assembly
  • Install optical components on support structures.
  • Align optical components.
  • Install baffling.
  • Wire mechanisms.
  • Install tie plate.
  • Install cast light-tight cover.
  • Install radiation shields.
  • Assemble vacuum jacket.

45
Summary of Issues
  • Baffling efficiency of input optics?
  • Alignment of image slicer?
  • Alignment of pupil and field mirror arrays?
  • Stability of all mounts, esp. the grating wheel?
  • Baffling efficiency within spectrograph?
  • Thermal gradients across CWS plate?

46
Scattering Analysis
47
Zero order from J grating 10.5º below camera axis
48
Ghost from camera tube wall reflection
49
Ghost Amplitude from OptiCAD Radiometer. For 400
launched rays Radiometer results for 20x20 bins
(1.668/(202))0.0044 rays/bin. Each bin
contains (2048/20)210485 pixels. Black paint
wall reflection 5 Assume Zero order is 10 Peak
ghost is (0.0044/10485).1 4.1E-8 per pixel
50
Camera forward reflections 2 from 2 last lenses
51
Detector back reflections For detector reflection
of 30
52
(No Transcript)
53
Ghost patches on detector
54
Ghost Amplitude from OptiCAD Radiometer. For 400
launched rays Radiometer results for 20x20 bins
(0.5777/(202))0.00144 rays/bin. Each bin
contains (2048/20)210485 pixels. Detector
reflection 30 Peak ghost is (0.00144/10485).3
4.1E-8 per pixel
55
  • With a reflection intensity of 4.1E-8 per pixel
    and a radial shift of about 0.8R what does shift
    and add do to this ghost?
  • The ghost is about 9x7mm and contains about 194
    000 pixels. If we shift and add the ghost over
    every pixel we will have a central patch of
  • (194 0004.1E-8)7.9E-3 per pixel.
  • This is a very bright central bump but in
    practice the real added ghost effect will be
    smaller because the ghost will lie in strips over
    the OH lines. A strip ghost over a single OH line
    will be
  • (9/.018)4.1E-82.0E-5 per pixel.

56
Non-Common Path Phase Errors
57
NIFS plus ALTAIR
  • Artificial star from ALTAIR
  • Differential flexure comparison
  • Phase Maps, common path optics in NIFS

58
  • NIFS common path optics.
  • Telescope focus -30mm to fill 2mm entrance
    aperture.
  • Common path optics near focus see large changes
    in footprint.

59
  • Phase maps from NIFS will be small.
  • We can make phase maps by warming the cryostat
    and moving the detector about -9mm. Our manual
    focusser is designed for about -3mm.
About PowerShow.com