05.12.2002 15:48
Beyond,
30 November 2002
With the entry of US weapons inspectors into Iraq, the fear of war looms ever larger. Obviously, the big questions are: Does Saddam Hussein have nuclear weapons? And if so, will he reveal them in time to avoid a large-scale conflict? A professor at Kansas State University is hoping that his research may help fight the war on terrorism by making it easier to detect weapons of mass destruction in general, and nuclear weapons in particular.
Douglas McGregor, a K-State associate professor of mechanical and nuclear engineering, has devised a portable detector that looks very much like a small, thin wafer. McGregor, who has been working on producing semiconductor neutron detectors for close to a decade, recently relocated his detector fabrication laboratory to K-State from the University of Michigan.
The detector, which is about the size of a shirt button, operates by fabricating a diode out of semiconductor material such as gallium arsenide (a material similar to silicon). According to McGregor, gallium arsenide was selected because of its low-noise characteristics at room temperature. The devices are coated with combinations of boron 10 or lithium in order to make the neutron sensitive.
When neutrons strike and are absorbed by the coatings, they undergo an immediate reaction, ejecting charged particles and leaving a trail of ionisation within the detector, constituting an easily discernable signature.
The wafers can also be tailored to the need of the user. The detector designs utilize a minimal amount of voltage, with some actually operating on their own internally generated voltage, thus eliminating the need for an external power supply.
"We can batch produce these and make hundreds at a time with one process run, whereas some alternative methods of applying boron, as used by other research laboratories, allow for fabrication of only one or two detectors at a time," says McGregor. "We can actually make these detectors for a cost of no more than to apiece, so that`s pretty low." A bargain basement price when you consider the potential payoff.
"We have stockpiles of weapons that we don`t want anyone tampering with," explains McGregor. "These detectors can be placed within the vicinity of these stockpiles and can monitor any change in the amount of neutrons that are being emitted by those weapons. Any alteration in the expected signal would set off an alarm and draw attention towards that facility."
While there are other neutron detectors currently available that are more efficient, they are larger and require far more voltage to operate. Previously, neutron detectors have been made of large tubes of gas. The gas in the tubes is ionised when neutrons pass through the tube. Thus, the tubes are bulky in size and require a fair amount of power to operate.
"Feasibly we could make our devices so that they could compete with what is out there right now," said McGregor. "The advantage is that our devices are thinner, smaller, and far more rugged than what is produced now."
"Unsurprisingly, although the professor has been conducting his detector research for many years, it took September 11th to generate real interest in his efforts.
The increased interest in this research has a lot to do with the fear of weapons of mass destruction being moved into this country," says McGregor. "These detectors would add to our ability to detect neutron radiation and nuclear weapons."
The U.S. Department of Energy`s Argonne National Laboratory, where McGregor has developed a long-standing collaboration with co-inventor Raymond Klann, is funding much of the detector research. Lawrence Livermore National Laboratory and other DOE programs contracts have contributed additional dollars.
When fully developed, it is hoped that these neutron detector devices could assist international weapons inspectors in detecting the presence of unauthorized nuclear weapons and materials, such as those feared to be in Iraq.
Nuclear terrorism focus shifting to research facilities
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