understanding mass transport in fuel cells using neutron imaging dr. david l. jacobson national...
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![Page 1: Understanding mass transport in fuel cells using neutron imaging Dr. David L. Jacobson National Institute of Standards and Technology 100 Bureau Drive](https://reader036.vdocuments.mx/reader036/viewer/2022070415/5697c0081a28abf838cc6c9a/html5/thumbnails/1.jpg)
Understanding mass transport in fuel cells using neutron imaging
Dr. David L. Jacobson
National Institute of Standards and Technology
100 Bureau Drive - Stop 8461
Bldg 235, Rm B185
Gaithersburg, MD 20899-8461
Phone: (301)975-6207
Fax: (301)926-1604
Email: [email protected]
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Overview
• Who are we and what is our mission
• Radiography
• Neutron Radiography
• NIST fuel cell role
• NIST Center for Neutron Research
• Fuel cell testing infrastructure
• Future goals and direction
• Access to the NIST facilities
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Radiography
• Roentgen Hand (1898) formed using xrays
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• Contrast is due to attenuation of radiation
• Scattering density of material can be extracted
• N - density of sample atoms per cm3
• I0 - incident neutrons per second per cm2
- neutron cross section in ~ 10-24 cm2
Radiography
0I tNeII 0
Sample
t
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x-ray cross sectionH D C O Al Si Fe
neutron cross section
Radiography
• Neutrons are the able to see hydrogen through heavy elements
• Comparison of the relative size of the x-ray and thermal neutron scattering cross section for various elements.
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Image Geometry
• Images are formed
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ij
• CCD images each pixel is a count value proportional to the light from the scintillator.• The transmission image below each pixel is a color or grayscaled value proportional to the
fraction of neutrons that make it through the sample.
What an image is
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Picture of the detector and sample holder assembly
Pinhole collimator
Neutron beam
Fuel cell Light tight box
Mirror
Lens
CCD chip
neutron to light converter
Computer
Neutron Camera
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Neutron Imaging Facility
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Neutron Image Quality
• Images are formed as shadows• Edges will be blurred by various effects• CCD camera and lens• Neutron to