Abstract
Progress in laser physics and accelerator physics has enabled us to use a new generation gamma-ray
beam, namely laser Compton scattering (LCS) gamma-ray beam. The LCS gamma-ray beam has
advantages that are an energy-tunable quasi-monochromatic gamma-ray beam. We have studied a
nondestructive assay using nuclear resonance fluorescence with a LCS gamma-ray beam. This assay can
be applied to the detection of nuclear materials hidden in cargo or a container. By measuring the
amounts of the levels of oxygen, nitrogen, and carbon, the type of explosive can also be identified. We
have demonstrated the detection of lead or melamine hidden in iron shields with thicknesses of
10-15 mm. Advanced laser technology is crucial to realize a compact gamma-ray source that can be
installed in seaports.
