megs p nrel presentation

8/9/2019 MEGS P NREL Presentation

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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

megs p nrel presentation

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