Fast determination of gold in large mass samples of gold ores by photoexcitation reactions using 10 MeV bremsstrahlung

Abstract

The determination of gold is based on the photoexcitation reaction ¹⁹⁷Au(γ,γ’)^197mAu with the half-life of 7.73 seconds and energy of emitted gamma-rays of 279 keV. Three 100 ml aliquots of coarsely ground Au-ore (grains <2 mm) corresponding to ca. 150–180 g were irradiated for 20 seconds with bremsstrahlung of maximum energy 10 MeV produced by a microtron at the electron beam current of 30–40 μA, 1–10 times reactivation was applied. After 3 seconds of decay, samples were measured for 20 seconds using scintillation or semiconductor gamma-spectrometry with the detection limits for an ideal sample down to 0.5 μg·g⁻¹ and 0.1–0.2 μg·g⁻¹ of Au, respectively. Content of U and Th undergoing photo-fission increases the detection limits several times.