Thursday, February 1, 2001 Using either x-ray or neutrons in
radiographic procedures, conventional material analysis methods
detect absorption of radiation as it passes through the
materials. However, if two of the materials have similar
absorption characteristics, then radiographs show very little.
Researchers at the National Institute of Standards and
Technology (NIST) believe they have a better way of examining
materials with similar absorption rates. It works a little like
the way light diffracts when passing through a glass of water.
Using low levels of radiation, the phase of the wave shifts at
the boundary between the two materials with different densities.
"Phase-sensitive imaging" yields images with greater detail,
especially at the boundaries and edges, according to Muhammad
Arif, a physicist at NIST. "With most radiography, a lack of
absorption translates into a lack of sensitivity needed when
detecting small cracks," says Arif. "Phase-sensitive imaging
shows these small cracks," he Potential appli