Scientists at Lawrence Livermore National Laboratory are developing a new gamma-ray scanning system that they say could greatly improve the ability of customs inspectors to detect nuclear weapons materials being smuggled into the US, without impeding the flow of commerce.

Using a 40-year-old mothballed accelerator with the improbable acronym T-REX, for Thomson-Radiated Extreme X-ray Source, the lab generated a laserlike beam of nearly one megavolt of mono-energetic gamma rays. Through a technique called nuclear resonance fluorescence, the researchers were able to excite atoms in a piece of lithium that was shielded behind sheets of lead and aluminum, thereby revealing the lithium’s presence.

The results show that the technique could locate even the lightest elements screened behind dense shielding, says principal investigator Christopher Barty. “We think that it’s going to open up a whole raft of detecting, assaying, and imaging applications.” Since the gamma rays produced can be tuned to the...

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