TOTAL-REFLECTION X-RAY-FLUORESCENCE SPECTROMETRY OF METAL SAMPLES USING SYNCHROTRON-RADIATION AT SSRL

It was demonstrated that a total reflection x-ray fluorescence spectro meter, using monoenergetic synchrotron radiation as the primary x-ray source, is suitable to measure the concentration of transmutational el ements in Cu and Fe metal matrices. In a typical irradiation of copper with 590 MeV protons or with spallation neutrons, where the damage do se is 0.4 dpa (displacement per atom), the calculated concentration of transmutational elements is Ni 25, Co 8 and Fe 8 mug g-1. The results show that the minimum detectable concentrations were lower than these values. The energy of the synchrotron radiation was set just below th e 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 mug g-1. In order to check systematically the possible geometric arrangeme nts of beam direction-reflector position-detector position, a new vacu um chamber was designed and tested. It provides all technical componen ts for remote control of the adjustment procedure to align the reflect or in total reflection geometry. Two ways of positioning the reflector in the beam, vertical to the plane of polarization and parallel to th at plane, were investigated, to find the best excitation conditions an d lowest limits of detection. A few pg corresponding to a concentratio n of ng g-1 of samples where the matrix can be easily removed as in aq ueous or acidic solutions and 50 ng g-1 concentration of metals in a l ight matrix as in oil were found as detection limits.