Nuclear Photonics: Gamma Rays Search for Concealed Nuclear Threats

Gamma rays are the most energetic type of light wave and can penetrate through lead and other thick containers. A powerful new source of gamma rays will allow officials to search for hidden reactor fuel/nuclear bomb material.

These gamma rays, called MEGa-rays (for mono-energetic gamma rays), are made by using a beam of fast-moving electrons to convert laser photons (light at a lesser energy) into the gamma ray part of the spectrum. The incoherent gamma rays can be tuned to a specific energy so that they predominantly interact with only one kind of material. A beam of MEGa-rays, for example, might be absorbed by the nuclear fuel uranium-235 while passing through other substances including the more common (but less dangerous) isotope uranium-238. That sort of precision opens the door to "nuclear photonics," the study of nuclei with light. "It is kind of like tunable laser absorption spectroscopy but with gamma-rays," says Chris Barty of Lawrence Livermore National Laboratory, who will present on MEGa-rays at CLEO: 2011.