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]
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
Radiography
• Roentgen Hand (1898) formed using xrays
• 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
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.
Image Geometry
• Images are formed
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
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
Neutron Imaging Facility
Neutron Image Quality
• Images are formed as shadows• Edges will be blurred by various effects• CCD camera and lens• Neutron to