Detecting Dirty Bombs from a Safe Distance

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User interface: The researchers developed software to operate the telescope and analyze data in real time. Credit: University of New Hampshire

The telescope comprises two different cylinder-shaped "scintillation" detectors that work in tandem, surrounded by large glass photomultiplier tubes. When a gamma ray hits the front detector, the energy is scattered and absorbed by the rear detector. The energy is then converted into visible light and detected by the highly sensitive photomultiplier tubes. The specific color and intensity of the light can identify the radioactive material involved, says Gerald Share, a visiting senior research scientist in the department of astronomy at the University of Maryland, who was not involved in the work.

"The instrument measures how much energy is deposited in each detector to calculate the total energy of the gamma ray," says Ryan. "This tells you what the radioactive isotope is." The researchers have hooked up the telescope to a laptop and developed software that is easy to control.

The researchers will present their work at the 2009 IEEE International Conference on Technologies for Homeland Security. "Since the 9/11 terrorist attacks, we realize we are in a dangerous world, and it is essential to put money into technologies like this," says Share. "We have no other choice."

Ryan says that the telescope could be used in a variety of national-security settings, such as for cargo inspections and to search for rogue nuclear weapons.