UNM’s Physics and Astronomy Department is working on a high-tech portable device that would track radioactive material and help prevent terrorism.
Paul Schwoebel, research professor of physics and astronomy, is studying a neutron source, a machine that collects neutrons through nuclear fusion. Schwoebel said neutron sources are primarily used to detect radioactive material, such as highly enriched uranium or plutonium. Schwoebel said he is studying the device in hopes of designing one that is smaller, to the point that one person would be able to carry it.
“The problem with this thing is that it’s so huge,” Schwoebel said. “There is no way that one person, or even a couple of guys, could carry it around for it to be of any use in the field.”
Schwoebel’s research is funded through the Department of Energy.
He receives $160,000 a year from the department which hopes to produce portable neutron sources that would allow agents guarding the borders of countries to reliably search cargo.
Schwoebel said unlike some radiation sources, which give off high levels of radiation that are easily detectable, uranium is harder to detect, making it difficult for law-enforcement agents to track using Geiger counters.
Uranium and plutonium give off only alpha particles, not alpha and beta particles, hence the need for special equipment to detect these materials, he said.
“There have been some cases in the news of people smuggling highly enriched uranium or plutonium out of some of those northern European countries,” Schwoebel said. “There are a lot of classified cases of the same thing going on.”
Schwoebel said the neutron source uses “active interrogation,” a kind of radiation sonar, irradiating potentially radioactive materials with the neutron source to stimulate a very small amount of nuclear fission that can be detected by the machine.
“When you activate the neutron source, you send out a big pulse of neutrons and they just go everywhere in every direction,” Schwoebel said. “If the neutrons hit radioactive material, it induces fission, and then you just listen with detectors and you’ll see a burst of radiation come out. It makes it light up like a Christmas tree.”
The neutron source at UNM costs about $100,000. Schwoebel is creating custom-made parts in the astronomy department’s machine shop and electric shop, but said the shop is outdated and not prepared to handle high-tech, delicate machinery.
“We have equipment here that breaks all the time and a lot of it is old equipment,” Schwoebel said. “And so we need the people who work in the machine shop and electric shop. A lot of the faculty here feels the same way, because they also use equipment that is old.”
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Schwoebel said not everyone is as excited for the neutron source to be used in the field as others.
“The public concern of using a neutron source to irradiate a cargo hold to learn whether or not highly enriched uranium is being smuggled is the fact that people might be in the cargo hold being smuggled as well,” Schwoebel said. “But a neutron source emits such low levels of radiation that it is like getting an X-ray. That’s kind of a controversial aspect of all of this.”
Schwoebel said he hopes to design a neutron source that is compact, reliable, reasonably priced and durable.
“A system like that, as it exists today, does not put out a lot of neutrons and so aren’t very useful,” he said. “The only ones that put out enough neutrons to be of any use are in a lab and are far too large to be carried by one person. You need to put out enough neutrons so that you can stimulate enough radioactivity in the material that you’re looking for so that you can see something.”
