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Editor's note: McGregor directs a new K-State facility -- the Semiconductor Materials and Radiological Technologies (SMART) Laboratory -- constructed for R & D of unique radiation detectors for many applications. New Technology Emerges: Ksu Engineer Makes Small, Inexpensive Neutron Detectors College students might think of Homer Simpson when they hear "nuclear reactor" and having Homer as safety inspector is a scary thought. Douglas McGregor is an associate professor of mechanical and nuclear engineering at K-State. He says these days, nuclear reactors are in safe operation all over the world. Several universities, Kansas State University among them, operate a nuclear reactor for experiments and research, and train future nuclear engineers. McGregor explained that a nuclear reactor produces and controls the release of energy from atoms by splitting the atomic nuclei in a process called nuclear fission. One of McGregor's current research projects is generating a lot of interest. For nine years he has been working on producing thin-film neutron detectors, and he says he has seen some great improvement. Simply put, neutron detectors detect neutrons -- neutral particles released from nuclear fission reactions. The thin-film neutron detectors use a coating applied over semiconducting material to help create reactions that allow the neutrons to be detected. McGregor currently has received two patents for the innovative devices, and two more applications have been filed. McGregor said that his research has attracted more interest over time. "When I was making devices that were one percent to four percent efficient, it didn't seem to interest people, but when I crossed 10 percent, then interest in the detectors became serious." One reason for stepped up interests is the possibility of the detectors being used to detect nuclear weapons, McGregor said. With the threat of terrorism and the constant struggles with the Middle East, many people think detectors could be a definite advantage in the conflict with Saddam Hussein and Iraq. While McGregor admits this is a possibility, he said that's not their only purpose. "These are not bomb detectors. They are neutron detectors, and some weapons emit neutrons." McGregor said there are many other practical uses, including monitoring neutron beams from nuclear reactors, and neutron film badges so people working around a reactor can measure the neutron levels. "I make them as neutron detectors, and they're used for a whole variety of things, not just for detecting weapons." Each detector is 5 mm - 6 mm in diameter, and no thicker than a dime. The detectors are batch processed onto gallium arsenide semiconducting wafers, yielding more than 60 detectors per each three-inch diameter wafer. At first glance the wafers look somewhat like a tiny pepperoni pizza. When McGregor first began working on the detectors, they were less than one percent efficient. This means that if 200 neutrons crossed through the detector, such a low level device would detect just one of those neutrons. McGregor said that his latest designs can yield up to 20 percent efficiency. "To my knowledge, our research group has the highest efficiency neutron detectors of this type." Other types of detectors, some using gas tubes, can reach up to 100 percent efficiency, McGregor said, but they are much larger, usually a foot long and several inches thick. "What I lose in efficiency, I gain in compact size." McGregor said his small designs also have advantages in lower manufacturing cost and energy used. While the larger detectors usually cost between $1,000 - $2000 each, McGregor said some of his compact models can sell for $10 - $40 each, with bulk sales making them even cheaper. The power needed to operate thin-film neutron detectors is another advantage. The gas tube detectors generally require 2,000 volts - 5,000 volts to operate, McGregor said. On the other hand, McGregor's detectors use less than 50 volts, and some of his designs can even create their own internal operating voltage. With all of the advantages that the thin-film neutron detectors exhibit, one thing is certain: McGregor has gained national attention for his work with K-State's nuclear reactor, and unlike Homer Simpson, it's a positive accomplishment.
Prepared by Derek Larson
Contact Douglas McGregor at
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