Mechanical Design of MEGS P Chris Converse 6/16/05.
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Transcript of Mechanical Design of MEGS P Chris Converse 6/16/05.
Mechanical Design of MEGS P
Chris Converse 6/16/05
What is MEGS P?
Photometer stage of the Megs B instrument, which exists as part of the Multiple EUV Grating Spectrometer (MEGS) for the EUV Variability Experiment (EVE) on the SDO Spacecraft
EVE Optics Package (OP)
EVE Electronics Box (EEB)
EVE on SDO Spacecraft
EVE Optical Package (OP)
CCD B Radiator
CCD A Radiator
Sunshade
Filter MechanismsBafflesAperture Doors
ESP
CCD Electronics Radiator
Kinematic Mounts
Alignment Cube
CCD Electronics
MEGS P
MEGS P
CCD Radiators
MEGS P
ESP
CCD Electronics
Kinematic Mounts
Aperture DoorsBaffles
Filter Mechanisms
CCD Detectors
Sunshade
MEGS Instrument
Case
EVE OP Exploded
CCD B
CCD A
B Grating 1
CCD Electronics Radiator
SAM
B Grating 2
A grating
MGS PElectrometers
Aperture Doors
Filter Mechanisms
MEGS B
MEGS A
MEGS Optic Overview
MEGS-P will track potential MEGS-B in-band sensitivity changesIRD silicon diode with Hydrogen Ly- (121.6nm) filter will detect Ly- of -1st order spectrum from first MEGS-B gratingLy- measurement will be used as a proxy for the other HI emissions at 75-103nm and also the HeI emissions at 45-59nm that vary like the HI emissions (see MEGS-P white paper)One “light” diode, one “dark”, for background subtraction
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 do…
Package this…
Grating 1
entrance slit
intermediate slit
“light” diode
“dark” diode
0th order trap
± 4ºFOV
± 2ºFOV
To Grating 2
Light in
No Requirements for:
Entrance Slit Adjustment 0th Order Trap Adjustment Intermediate Slit Adjustment Diode Adjustment
Requirements Optical FOV
±2º, except for 0th order trap which must accept ±4º diode must capture complete ±2º FOV of Megs P band
EMI shielding diodes- 1/2” aluminum match EM 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
Requirements (cont.) Electrical
ground strap –top of EEB to MEGS P cover metallic items to be grounded to chassis ground. (No charge
islands) thermistor to monitor diode temperature no external dielectrics, unless shielded by > 0.06” aluminum
Grating adjustment: ±.050”, .001” increments (Equivalent to .003”
increments at slit. Slit width provides .020” margin)) ability to view intermediate slit for grating alignment design for 3x max. acceleration (54g’s), about 20lbf
Particulate mitigation blind holes & vented screws
Accommodate purge port
Design goals
Reduce number of parts and interfaces between parts
Improve manufacturability Combine diode assembly and electrometer boards
for simplicity & modularity Improve 0th order trap efficiency Accessibility for grating alignment either
autonomously or when mounted to MEGS Utilize existing board layout for electrometers Grating install without needing to hold springs or
retainers
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
Megs P on MEGS housing with ESP
MEGS B Baffles
MEGS housingESP MEGS P
MEGS “tunnel”
MEGS P
15.5”
21.5”
The Complete Package….it’s small
8.5”
MEGS P Subassemblies
slit mount
electrometer/diode
grating mount
housing
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
Two Views of Slit Assembly
0th order trapcel
Trap enclosure
Intermediate slit
Entrance slit
Slit mount plate
0th Order Light Trap
X1012 attenuation Utilizes a narrow angle, truncated wedge of
black specular glass(2º 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
0th Order Trap Cutaways
Side view Top view
Intermediate Slit
0th order
science
Trap celTrap cel
Intermediate Slit
MEGS P
Slit mount
Trap enclosure
Electrometer/Diode Assembly Provides a single mounting and enclosure for
electrometer boards and diodes Hermetic wire feedthrough to diodes Simple interface to Megs P housing allows
removal and troubleshooting independent from Megs P.
Vents through Megs P housing wall Thermistor bonded to housing with Stycast
proximal to diodes
Electrometer Assembly
Potted feedthroughElectrometer boards
Ly- filter
Nano connector
Housing
“dark” diode
“light” diode
Diode cover
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
Two Views of Housing
CollarFor
connector
Grating mount points Grating mount surface
Cover o-ring groove
Grating Mount
Mounts grating directly to housing Provides ±.050” adjustment at each pad Pad spacers machined to .001” precision Provides .003” incremental adjustment
across intermediate slit Springs hold grating against spacers to 54g’s Grating rests on brass pads, and is
constrained by delrin fingers on beryllium copper leaf springs
Grating Mount Exploded View
Grating cover
Grating backing plate
Grating
Retaining spring
Retaining springs
Retaining springs
MEGS P housing
Grating Mount- Back Side Section
Grating
Brass seat pin
spacer
BCu spring
Delrin finger
BCu spring
Grating Mount- Top Section
Grating
Brass seat pin
Spacer
Delrin fingerBCu spring
Baffling
Higher order baffling Two baffles, mounted to housing floor and ceiling Clip ±4º FOV
Entrance Slit ±4º baffle inside entrance slit TBD
Higher Order Baffles
Baffle on floor
Baffle on ceiling
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
Alignment Inspection
Intermediate Slit0th order light
Grating coverElectrometer connector
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
of MEGS P housing