Total reflection X-ray fluorescence spectrometry of metal samples using synchrotron radiation at SSRL

It was demonstrated that a total reflection x-ray fluorescence spectrometer, using monoenergetic synchrotron radiation as the primary x-ray source, is suitable to measure the concentration of transmutational elements in Cu and Fe metal matrices. In a typical irradiation of copper with 590 MeV protons or with spallation neutrons, where the damage dose is 0.4 dpa (displacement per atom), the calculated concentration of transmutational elements is Ni 25, Co 8 and Fe 8 μg g−1. The results show that the minimum detectable concentrations were lower than these values. The energy of the sychrotron radiation was set just below the K-edge energy of the matrix element, eliminating the large peak due to the matrix. As an example, in the case of a Cu (Z = 29) matrix, the minimum detectable concentration for Ni (Z = 28) was as low as 3 μg g−1. In order to check systematically the possible geometric arrangements of beam direction–reflector position–detector position, a new vacuum chamber was designed and tested. It provides all technical components for remote control of the adjustment procedure to align the reflector in total reflection geometry. Two ways of positioning the reflector in the beam, vertical to the plane of polarization and parallel to that plane, were investigated, to find the best excitation conditions and lowest limits of detection. A few pg corresponding to a concentration of ng g−1 of samples where the matrix can be easily removed as in aqueous or acidic solutions and 50 ng g−1 concentration of metals in a light matrix as in oil were found as detection limits.