Nondestructive Detection of Heavily Shielded Materials by Using Nuclear Resonance Fluorescence with a Laser-Compton Scattering γ-ray Source

We perform a proof-of-principle experiment for a nondestructive method for detecting the elemental and isotopic composition of materials concealed by heavy shields such as iron plates with a thickness of several centimeters. This method uses nuclear resonance fluorescence (NRF) triggered by an energy-tunable laser-Compton scattering (LCS) γ-ray source. One-dimensional mapping of a lead block hidden behind 1.5-cm-thick iron plates is obtained by measuring an NRF γ-ray of a lead isotope 208 Pb. We observe a 5512-keV γ-ray from 208 Pb excited by the quasi-monochromatic LCS γ-rays with energies up to 5.7 MeV. The edge position of the lead block is consistent with the exact position within the uncertainty.