Experts approximate that more than 110 million land mines--hidden disasters waiting to happen--are buried around the world in nearly 70 countries. And at the rate people are currently working to find and remove these threats, the United Nations' Landmine Database estimates the job will take another 1,100 years. Potential victims don't have that long to wait, and so researchers at the Pacific Northwest National Laboratory have come up with a new kind of land mine detector, the Timed Neutron Detector (right). The device, which the scientists say should prove easier to use and more affordable than current methods, was field-tested in September and will be presented by principal investigator Richard Craig on November 14 in Washington, D.C., at the international meeting of the American Nuclear Society and the European Nuclear Society.
The instrument uses neutrons to pick up on hydrogen used in casings and explosives found in both plastic and metal land mines. A neutron source, about the size of a pager, holds a small amount of californium-252. As the element decays, it emits neutrons, which electronics in the instrument then "time tag," noting when the fission occurred. The neutrons shoot out into the soil, where they lose energy if they interact with hydrogen in a mine. These less energetic, slow neutrons are reflected back toward the detector; nonradioactive helium-3 in low-pressure pipes collects them and emits electrons. By way of other circuitry, these electrons translate into the desired information: whether a land mine was encountered or not. The scientists say that a person operating the detector would not receive any more radiation than if they were on a cross-country flight.