Two-dimensional imaging of heavily shielded materials by NRF with laser-compton photon beam

Experimental demonstration of a two-dimensional imaging was done by an emission radiography method based on nuclear resonance fluorescence (NRF) and a gamma-ray spectrometry. A wedge-shaped specimen made of natural lead, which simulated a special nuclear material, hidden in a radiation-shielding box made of natural iron was prepared. A photon beam of 5600 keV was generated using an electron storage ring TERAS of AIST, via the laser Compton scattering. The photon beam was collimated to 5 mm in diameter, and incident on the specimen through the radiation-shielding box. The energy spectrum of NRF gamma-rays emerged from the specimen was measured with a high-purity germanium gamma-ray spectrometer, and the full-energy peak was analyzed. The peak intensity was measured in various position to visualize the specimen by 2-D radiograph as we scan the specimen with respect to the photon beam. We successfully obtained a 2-D radiograph of the specimen.