X-ray Fluorescence (XRF) Assay Using Laser Compton Scattered (LCS) X-rays

Abstract

Laser Compton Scattered (LCS) X‐rays are produced as a result of the interaction between accelerated electrons and a laser beam. The yield of LCS X‐rays is dependent on the laser power, angle of collision between interacting particles, and the electron linear accelerator’s (linac) electron beam energy and its current. One of our research goals at the Idaho Accelerator Center (IAC) focuses on applications such as detection and imaging of fissionable isotopes for nuclear non‐proliferation, safeguards and homeland security. Quasi monochromatic LCS X‐rays offer much better signal‐to‐noise ratios for such applications. The energy of LCS X‐rays is tunable, that enable element‐specific analysis. Two sharp 36.5 keV and 98.4 keV LCS peaks were observed in two separate experiments based on electron beams tuned at 32 MeV and 37 MeV, that were brought in collision with the (Power)peak = 4 GW Nd.YAG laser operating at 532 nm and 266 nm wavelengths. The linac was operating at 60 Hz with an electron beam pulse length of about 50 ps and a peak current of about 7 A. We exploited X‐ray fluorescence (XRF) techniques to identify elemental Kα1, Kα2, and Kβ1 lines in a high‐purity germanium (HPGe) detector, with a 0.5 mm thick Beryllium (Be) absorbing layer, emitted from tin (Sn), cadmium (Cd), silver (Ag), gold (Au), and lead (Pb) foils with thicknesses ranging from 25–500 μm, following absorption of 36.1 keV and 98.4 keV LCS X‐rays. These reference foils were used for the proof of principle, and some have atomic numbers near to that of relevant fission products.