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With additional engineering advancements, the method could be scaled up and used to scan trucks and shipping containers at ports of entry, providing a powerful new tool to detect concealed, dangerous radioactive material. The researchers described their proof-of-concept experiments in a research paper published March 22, 2019 in the journal Science Advances.
"Traditional detection methods rely on a radioactive decay particle interacting directly with a detector. All of these methods decline in sensitivity with distance," said Robert Schwartz, a physics graduate student at UMD and the lead author of the research paper. "The benefit of our method is that it is inherently a remote process. With further development, it could detect radioactive material inside a box from the length of a football field."
Material - Emits - Decay - Particles - Particles
As radioactive material emits decay particles, the particles strip electrons from -- or ionize -- nearby atoms in the air, creating a small number of free electrons that quickly attach to oxygen molecules. By focusing an infrared laser beam into this area, Schwartz and his colleagues easily detached these electrons from their oxygen molecules, seeding an avalanche-like rapid increase in free electrons that is relatively easy to detect.
"An electron avalanche can start with a single seed electron. Because the air near a radioactive source has some charged oxygen molecules -- even outside a shielded container -- it provides an opportunity to seed an avalanche by applying an intense laser field," said Howard Milchberg, a professor of physics and electrical and computer engineering at UMD and senior author of the research paper, who also has an appointment at IREAP. "Electron avalanches were among the first demonstrations after the laser was invented. This is not a new phenomenon, but we are the first to use an infrared laser to seed an avalanche breakdown for radiation detection. The laser's infrared wavelength is...
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