mESEM miniaturized Environmental Scanning Electron Microscope

1
mESEM(miniaturized Environmental Scanning
Electron Microscope)

• 2005 Marshall NASA Academy
• Final Project Presentation
• by Michael Lamberty
• under supervision of
• Brian Ramsey and Jessica Gaskin
• August 12, 2005

2
Objectives

• Develop a feed mechanism and sample chamber for a
  mESEM that
• ? loads samples (rocks, soil)
• ? feeds samples to mESEM proper
• ? expels samples after imaging
• ? maintains vacuum
• ? minimizes contamination
• ? minimizes cross-contamination

3
SEMs 101
1 vacuum pump 2 electron gun 3 column 4
sample chamber 5 detectors

• Operation
• An SEM is a specialized particle accelerator. It
  fires a beam of electrons at a sample. Energy
  emitted from the sample provides data on its
  composition and structure.

4
Why Send A mESEM to Mars?
Astrobiology ? image micro-fossils in
Martian rocks ? current instruments lack
sufficient resolution

• Analyze rocks and minerals
• ? characterize structure and chemical composition
  
• ? determine conditions at and after formation
• ? evaluate in situ resource potential

5
Martian Environmental Conditions
6
Sample Chamber/Feeder Design
? disposable sample pockets ? continuous
web ? integrated vacuum chamber
1 cleaning chambers 2 sample inlet lock 3 web
supply roll 4 carrier web 5 guide
rollers 6 sample pocket 7 sample 8 electron
gun 9 column assembly 10 detectors 11 drive
rollers 12 web cutter 13 sample outlet
lock 14 vacuum chamber 15 vacuum pump
7
Proof-of-Concept Model
A web supply roll 2-ply 1-mil polyimide
web B guide rollers split to pass
pockets C lower drive roller split to pass
pockets (no drive shown) D upper drive
roller E sample pocket F drive roller
bias biases drive rollers together to grip web
D
A
C
E
B
B
B
B
F
D
A
C
web start
web end
8
Feeder Operation (1 of 2)
A
B
A
B
?
feeder on standby
pocket unrolled
A
A
B
?
pocket ready for sample
pocket close-up
Notes A - sample cleaner location B - mESEM
column location
9
Feeder Operation (2 of 2)
A
A
B
?
sample in pocket
pocket close-up
A
B
A
B
?
?
sample and pocket expelled
sample ready for mESEM imaging
Notes A - sample cleaner location B - mESEM
column location
10
Conclusions

• Design concept validated
• ? concept demonstrated to be useful
• ? webs and sample pockets constructed
• ? model advanced webs, fed samples, expelled
  samples
• Further development
• ? construct scale mechanical model
• ? integrate with mESEM electronics
• ? simulate Mars operation
• ? develop cleaning process
• ? evaluate sealed sample pockets

11
Questions?