Tiny device can detect hidden nuclear weapons, materials
ARGONNE, Ill. (June 21, 2002) - 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.
When fully developed, the device could assist international
inspectors charged with preventing smuggling and unauthorized use of nuclear
weapons and materials.
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.
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.
"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."
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.
The wafers are made by co-inventor Doug McGregor at Kansas State
University, who uses inexpensive, conventional microchip-processing techniques,
Klann said. They can be tailor-made for specific applications by varying the
type and thickness of the coating.
Compared to other neutron detectors, Klann's have a number of
advantages.
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.
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.
Klann's team also found that detection is improved by etching the
wafer with cylindrical holes, like the dimples on a golf ball.
"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."
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.
Other possible uses for GaAs-based detectors include high-vacuum
space applications or any other work requiring neutron detection.
Development of the wafer and detector was funded by the U.S.
Department of Energy's Office of Science.
Argonne National Laboratory brings
the world's brightest scientists and engineers together to find exciting and
creative new solutions to pressing national problems in science and technology.
The nation's first national laboratory, Argonne conducts leading-edge basic
and applied scientific research in virtually every scientific discipline. Argonne
researchers work closely with researchers from hundreds of companies, universities,
and federal, state and municipal agencies to help them solve their specific
problems, advance America 's scientific leadership and prepare the nation for
a better future. With employees from more than 60 nations, Argonne is managed
by UChicago
Argonne, LLC for
the U.S.
Department of Energy's Office
of Science.
For more information, please
contact Steve McGregor (630/252-5580 or media@anl.gov)
at Argonne.
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