- A small, portable detector for finding concealed nuclear
weapons and materials has been developed by the U.S. Department of Energy's
Argonne National Laboratory.
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- When fully developed, the device could assist international
inspectors charged with preventing smuggling and unauthorized use of nuclear
weapons and materials.
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- The heart of the Argonne device is a small wafer of gallium
arsenide (GaAs), a semiconducting material similar to silicon. When coated
with boron or lithium, GaAs can detect neutrons, such as those emitted
by the fissile materials that fuel nuclear weapons. Patents are pending
on several detectors and their components.
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- The wafers are small, require less than 50 volts of power
and operate at room temperature. They also can withstand relatively high
radiation fields and do not degrade over time.
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- "The working portion of the wafer is about the diameter
of a collar button, but thinner," said Raymond Klann, who leads the
group from Argonne's Technology Development Division that developed the
wafer and detector. "It is fairly straightforward to make full-sized
detector systems the size of a deck of cards, or even smaller. Something
that small can be used covertly, if necessary, by weapons inspectors to
monitor nuclear facilities."
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- The key to detection, he said, is to coat the gallium-arsenide
with something like boron or lithium. When neutrons strike the coating,
they produce a cascade of charged particles that is easy to detect.
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- The wafers are made by inexpensive, conventional microchip-processing
techniques, Klann said. They can be tailor-made for specific applications
by varying the type and thickness of the coating.
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- Compared to other neutron detectors, Klann's have a number
of advantages.
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- One common type of neutron detector is based on a tube
of gas, which is ionized when neutrons pass through the tube. These detectors
are larger in size and require more power than the GaAs detector.
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- Another common neutron detector uses silicon semiconductors.
Compared to the GaAs wafer, silicon-based detectors use more power, require
cooling and degrade more quickly when exposed to radiation.
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- Klann's team also found that detection is improved by
etching the wafer with cylindrical holes, like the dimples on a golf ball.
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- "We're testing various coating materials and thicknesses,"
he said, "as well as various combinations of hole sizes and spacings
to find the best configurations for specific applications."
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- Klann's group has built and successfully demonstrated
prototype detectors. Argonne is now looking for commercial partners interested
in developing the detectors for the commercial marketplace.
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- Other possible uses for GaAs-based detectors include
high-vacuum space applications or any other work requiring neutron detection.
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- Development of the wafer and detector was funded by the
U.S. Department of Energy's Office of Science and the Spallation Neutron
Source project.
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- The nation's first national laboratory, Argonne National
Laboratory conducts basic and applied scientific research across a wide
spectrum of disciplines, ranging from high-energy physics to climatology
and biotechnology. Since 1990, Argonne has worked with more than 600 companies
and numerous federal agencies and other organizations to help advance America's
scientific leadership and prepare the nation for the future. Argonne is
operated by the University of Chicago as part of the U.S. Department of
Energy's national laboratory system.
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- Editor's Note: The original
news release can be found at
- http://www.anl.gov/OPA/news02/news020621.htm
-
- Note: This story has been
adapted from a news release issued by Argonne National Laboratory for
journalists and other members of the public. If you wish to quote from
any part of this story, please credit Argonne National Laboratory as
the original source. You may also wish to include the following link in
any citation:
- http://www.sciencedaily.com/releases/2002/06/020627010016.htm
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