Nuc Weapons Detection

["Estabrooks, Bates (IHK) " <IHK@Y12.doe.gov>]

Tiny Device Can Detect Hidden Nuclear Weapons, Materials



This small wafer could become the key component in small, portable detectors

for finding concealed nuclear weapons and materials. Argonne National

Laboratory photo.	

Argonne - Jun 28, 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 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 and the Spallation Neutron Source project. 

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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