Isotope-selective radiography and material assay using high-brilliance, quasi-monochromatic, high-energy photons

We demonstrate the possibility to directly detect microgram amounts of the isotope Li-7 using a quasi-monochromatic high-energy photon beam. The isotope selective detection is based on a witness scatterer absorbing and re-emitting photons via nuclear resonance fluorescence. This enables the detection of isotopes with microgram accuracy at long distances from the actual sample. Further, we demonstrate that the technique can deliver quantitative information without specific knowledge of the photon flux and no spectral capabilities or knowledge of the resonance fluorescence cross section. Detection of low-atomic-weight isotopes screened by heavy shielding is also shown. The techniques described are applicable to all next-generation, ultrahigh brilliance, laser-Compton light sources currently under construction. (C) 2022 Optica Publishing Group