New Way to Sniff Out Dirty Bombs

Wednesday, November 10, 2010 @ 04:11 PM gHale

There is now a way to detect a concealed source of radioactive material without searching containers one by one.
Detection of radioactive material concealed in shipping containers is important in the early prevention of “dirty” bomb construction. Researchers base the concept on the gamma-ray emission from the radioactive material that would pass through the shipping container walls and ionize the surrounding air.
The facilitated breakdown of the air in a focused beam of high-power, coherent, terahertz or infrared radiation would then be an indicator of the presence of the radioactive material, said researchers at the University of Maryland. They could detect the gamma rays coming through the container walls by a pulsed electromagnetic source of duration between 10 ns to microseconds.
The team evaluated several candidate sources for this detection, including a 670-GHz gyrotron oscillator with 200-kW, 10-┬Ás output pulses and a TEA CO2 laser with 30-MW, 100-ns output pulses. A system based on the 670-GHz gyrotron would enhance sensitivity and a range exceeding 10 m.
“It is not yet clear whether this approach to detection of nuclear material is practical,” said Victor Granatstein, a professor at Maryland and first author of a paper on the subject, “but it is worth pursuing since it might impact an important need related to National Security.”

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