 |
CHICAGO — Researchers at Argonne National Laboratory’s Technology Development Division have invented a wafer that can detect neutron radiation from concealed nuclear weapons.
An inexpensive handheld device that incorporates the wafer could eventually be used in airports by law enforcement agencies or by weapons inspectors. “Generally, you shouldn’t be detecting neutrons at all, and if they’re there, it’s probably coming from something that people shouldn’t have, whether it’s a weapon, a radioactive source, or fissionable material,” says research group leader Raymond Klann.
The fingernail-sized wafer, about 200 microns thick, is made of gallium arsenide, a semiconducting material similar to silicon. An active area in the center, about 5 millimeters in diameter and between 10 and 20 microns thick, is coated with boron or lithium. When neutrons strike the coating, they produce a stream of charged particles that’s easy to detect with commercial detectors.
The wafers operate at room temperature, can be powered by batteries, can withstand relatively high levels of radiation, and do not degrade over time. They’re made with conventional microchip fabrication techniques and can be tailored to different uses by varying the coating material and the thickness.
The wafer becomes more effective if the active area is etched with holes about 3.5 microns in diameter, creating a “pock-marked” effect, Klann said. The group is experimenting with various hole depths, ranging from 1 to 20 microns.
Adjustments in the coating can make the wafer position-sensitive, so that it can detect not only whether there are neutrons, but also which direction they’re coming from, Klann said. By employing several of the devices, users can narrow the location of suspicious materials to within a few feet.
The wafers have been fabricated in facilities at the University of Michigan and Kansas State for about $100 each. Combining the wafer with off-the-shelf electronic components, Klann can build a palm-size detector for less than $2,000.
Klann says the device could interest commercial detector manufacturers, and Argonne is actively looking for commercial partners. Although gamma-ray detectors are used for weapons detection in airports, he knows of no commercial neutron-detection product that fills that particular niche. Much larger neutron detection devices have been built in government labs for several hundred thousand dollars each for specific defense applications, but none have been commercialized.
Patent applications have been filed for both the coated wafer and the pocked surface treatment.
The initial work was funded through the Department of Energy and grants from within Argonne itself. Klann is seeking further funding of about $200,000 over the next two years, as well as additional funding from agencies or companies interested in developing devices for specific applications.