Figure 1: Illustration of the imaging method using a low-energy nuclear reaction radiation source.

(a) Low-energy nuclear reaction imaging relies upon the source of monochromatic photons via a nuclear reaction between an ion accelerated to MeV-scale energy and a target. Gamma rays at discrete energies are produced from nuclear excited states of the product nucleus, with some reactions also producing neutrons. The collimated, penetrating radiation from the nuclear reaction source is used to perform transmission radiography of a shielded object, while neutron/gamma discriminating detectors detect the signature of nuclear fission. (b) Photon spectrum from the ¹¹B(d,nγ)¹²C reaction measured with a LaBr scintillation detector. The detector is capable of measurement of the 15.1 MeV peak despite of small crystal size. It is also able to resolve the full energy peaks (labeled as “f”) and single (“s”) and double (“d”) escape peaks. Also shown are “j” and “k” peaks corresponding to other nuclear transitions in the target. (c) Energy-dependent attenuation for several elements (4.438 MeV and 15.1 MeV gamma energies from the ¹¹B(d,nγ)¹²C reaction are shown as dashed lines).