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Mechanical Design
of MEGS P
Chris Converse
Mechanical Engineer
Laboratory for Atmospheric and Space Physics
University of Colorado, Boulder, CO
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EVE Optics Package (OP)
EVE Electronics Box (EEB)
EVE on SDO Spacecraft
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3
Whycare about the Solar EUV?
EUV (Wavelength
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EVE Optical Package (OP)
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EVE OP Exploded
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CCD B
CCD A
B Grating 1
CCD Electronics Radiator
SAM
B Grating 2
A grating
MEGS P
Electrometers
Aperture Doors
Filter Mechanisms
MEGS B
MEGS A
MEGS (Multiple EUV Grating Spectrometer)
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MEGS-B
Entrance slit
0th order,
1st grating
First grating (rulings horizontal)
MEGS-P diode
(Ly-; -1st order)
MEGS-B Primary science beam
What Megs P will doMEGS-P will track potential MEGS-B in-band sensitivity changes
IRD silicon diode with Ly- (121.6nm) filter will detect Ly- of -1st order spectrumfrom first MEGS-B grating
One light diode, one dark, for background subtraction
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Package this
First Grating
entrance slit
intermediate slit
light diode
dark diode
0th order trap
s 4FOV
s 2FOV
To Grating 2
Light in
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Requirements Optical FOV
s2, except for 0th order trap which must accept s4
diode must capture complete s2 FOV of Megs P band
EMI shielding
diodes- 1/2 aluminum
match EMI shielding between light and dark diode
electrometer boards- .20 aluminum Visible Light Attenuation schemes
o-ring
labyrinth
black nickel on surfaces
0th order light trap attenuate to 1012 light tight to MEGS B cavity (beyond intermediate slit)
Higher order light attenuation
baffles between grating and intermediate slit
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Requirements (cont.)
Electrical ground strap top of EEB to MEGS P cover
metallic items to be grounded to chassis ground. (No chargeislands)
thermistor to monitor diode temperature
no external dielectrics, unless shielded by > 0.06 aluminum Grating
adjustment: s.050, .001 increments (Equivalent to .003increments at slit. Slit width provides .020 margin))
ability to view intermediate slit for grating alignment
design for 3x max. acceleration (54gs), about 20lbf
Particulate mitigation blind holes & vented screws
Accommodate purge port
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Design goals
Reduce number of parts and interfaces betweenparts
Improve manufacturability
Combine diode assembly and electrometer boardsfor simplicity & modularity
Improve 0th order trap efficiency
Accessibility for grating alignment eitherautonomously or when mounted to MEGS
Utilize existing board layout for electrometers
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Layout Overview
MEGS P mounts to MEGS housing
Clearance to accommodate ESP instrument
Connector access for electrometer Purge integration
Ground strap from cover to EEB
Filter wheel interface via MEGS housing
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Megs P on MEGS housing with ESP
MEGS B Baffles
MEGS housingESP MEGS P
MEGS tunnel
MEGS P
15.5
21.5
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The Complete Package.its small
8.5
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MEGS P Subassemblies
slit mount
electrometer/diode
grating mount
housing
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Slit Mount
Provides common mounting for entrance slit,
intermediate slit, and 0th order trap
Mounts to Megs P housing
Light tight labyrinth at entrance slit
Protrudes into MEGS tunnel of MEGS
housing
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Two Views of Slit Assembly
0th order trap
celTrap enclosure
Intermediate slit
Entrance slit
Slit mount plate
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0th Order Light Trap
X1012 attenuation
Utilizes a narrow angle, truncated wedge of
black specular glass(2 included angle)
Provides 12 discreet bounces before the light
either reverses itself to exit trap, or before it
reaches the end of the trap
Modeled and validated with Zmax
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0th Order Trap Cutaways
Side view Top view
Intermediate Slit
0th order
science
Trap celTrap cel
Intermediate Slit
MEGS P
Slit mount
Trap enclosure
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Electrometer/Diode Assembly
Provides a single mounting and enclosure forelectrometer boards and diodes
Hermetic wire feedthrough to diodes
Simple interface to Megs P housing allowsremoval and troubleshooting independentfrom Megs P.
Vents through Megs P housing wall
Thermistor bonded to housing with Stycastproximal to diodes
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Electrometer Assembly
Potted feedthroughElectrometer boards
Ly- filter
Nano connector
Housing
dark diode
light diode
Diode cover
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MEGS P Housing
Provides common mount for grating, slit
assembly, and electrometer/diode assembly
Mounts to MEGS housing using location pins
or equivalent
Angle of grating mounting surface machined
into housing, allowing all orthogonal fits to
grating
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Two Views of Housing
Collar
For
connector
Grating mount points Grating mount surface
Cover o-ring groove
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GratingMount
Mounts grating directly to housing
Provides .050 adjustment at each pad
Pad spacers machined to .001 precision
Provides .003 incremental adjustmentacross intermediate slit
Springs hold grating against spacers to 54gs
Grating rests on brass pads, and isconstrained by Delrin fingers on berylliumcopper leaf springs
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GratingMount Exploded View
Grating cover
Grating backing plate
Grating
Retaining spring
Retaining springs
Retaining springs
MEGS P housing
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GratingMount- Back Side Section
Grating
Brass seat pin
Spacer
BCu spring
Delrin finger
BCu spring
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GratingMount- Top Section
Grating
Brass seat pin
Spacer
Delrin fingerBCu spring
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Baffling
Higher order baffling
Two baffles, mounted to housing floor and ceiling
Clip 4 FOV
Entrance Slit
4 baffle inside entrance slit TBD
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Higher Order Baffles
Baffle on floor
Baffle on ceiling
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Alignment
With housing cover off, grating aligned by
locating visible, 0th order band on 0th order
trap slit.
After grating positioned with shims, final flight
spacers machined to .001 precision
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Alignment Inspection
Intermediate Slit0th order light
Grating cover
Electrometer connector
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Light Seal Summary
MEGS P Housing to MEGS Housing O-ring
Entrance slit labyrinth against MEGS housing
bulkhead
0th order trap mount - labyrinths
Housing cover O-ring
Grating cover O-ring
Electrometer O-ring against inside surface ofMEGS P housing
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Mission Accomplished
All requirements met
Reduce part count and # interfaces >50%
Improve manufacturability
Combined diode assembly and electrometer boards forsimplicity & modularity
Improve 0th order trap efficiency
Accessibility for grating alignment either autonomously orwhen mounted to MEGS
Utilize existing board layout for electrometers