Image Processing Reference
In-Depth Information
Figure4.30 GRIS images of depleted uranium (left) and plutonium fuel rods (right).
range is centered around 400 keV, which eliminates the lower-energy uranium-
induced gamma rays, and shows the plutonium radiating through the uranium
shielding. The gamma-ray images are overlaid onto a visible-light image of the
room containing the nuclear material. A lightly traced outline of the container is
overlaid onto the gamma-ray images.
This technique can be applied to problems of contamination and container
contents verification, since the gamma rays can carry information about the
contents of a container through its walls. This system can also be used for on-
site inspection and characterization of nuclear weapons and nuclear materials for
arms-control purposes, as shown in the illustration in Fig. 4.31. Figure 4.32 shows
a GRIS image of a Peacekeeper missile with its 10 warheads contained within. The
image was made without having to move the missile out of its silo or remove the
nose cone, which would compromise the readiness of the missile.
The x-ray and gamma-ray wavebands are the shortest-wavelength, highest-
energy wavebands in the electromagnetic spectrum as we presently know it.
Perhaps in the future, scientists will create a name for a new band of light
beyond gamma rays, associated with some undiscovered set of phenomena.
The penetrating power of this high-energy light makes it extremely useful for
imaging through material that is opaque to lower-energy light. X-ray and gamma-
ray imaging also yields information about the workings of nuclear reactions
and magnetic phenomena that generate high-energy light through nonthermal
processes, both on Earth and in the cosmos.
The next chapter explores acoustic imaging, an alternative to imaging with light.
Scientists frequently encounter situations where they cannot image objects with
light at any wavelength, either because it would be dangerous to the subject being
imaged, or because material between the imaging system and the object being
imaged is too thick or dense to allow the passage of light. Acoustic imaging offers
an alternative to lightwave imaging that overcomes some of these difficulties. It
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