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27 June 2002
Source:
http://usinfo.state.gov/cgi-bin/washfile/display.pl?p=/products/washfile/latest&f=02062701.glt&t=/products/washfile/newsitem.shtml
US Department of State
International Information Programs
Washington File
_________________________________
27 June 2002
U.S. Researchers Develop Tiny Nuclear Detector
(Device can detect hidden nuclear weapons) (750) The U.S. Department of Energy's Argonne National Laboratory has developed a small, portable detector for finding concealed nuclear weapons and materials. According to a June 21 press release, the heart of the Argonne detector is a small wafer of gallium arsenide -- a semiconducting material similar to silicon -- which when coated with boron or lithium can detect the neutrons emitted by the fissile materials that fuel nuclear weapons. The wafers are small, require less than 50 volts of power and operate at room temperature. When fully developed, the detector could assist international inspectors working to prevent terrorists from smuggling or using nuclear weapons and materials. According to Raymond Klann, who led the research team that developed the wafer and detector, making full-sized detector systems the size of a deck of cards or even smaller is now a fairly straightforward process. "Something that small can be used covertly, if necessary, by weapons inspectors to monitor nuclear facilities," he said. Following is the text of the press release: (begin text) Argonne National Laboratory June 21, 2002 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 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. (end text) (Distributed by the Office of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)