Characterisation of radioactive decay series by digital autoradiography, part 2: Experimental evidence of time and space coincidences (TSCs) on geo-materials

Abstract

The BeaQuant gas detector is a real-time digital autoradiography system that sequentially acquires alpha and beta emissions from natural decay chains. Each emission is identified according to the type of particle emitted (alpha or beta), and the time and position of emergence in two dimensions. The experimental data generated were interpreted using an algorithm to identify Time and Space Coincidences (TSCs). Three different TSCs were detected on a thin section of uranium ore at secular equilibrium. These α/α, α/α/α and β/α coincidences come from three short-lived radionuclides: ²¹⁵Po and ²¹⁹Rn in the ²³⁵U chain, and ²¹⁴Po in the ²³⁸U chain. The distribution of the differences in arrival times of the particles forming a coincidence was analysed in terms of half-life. This analysis confirmed that these three coincidences originated from these three radionuclides, the periods having been found experimentally. The theoretical calculations of the number of coincidences confirm those obtained by the algorithm for analysing the experimental autoradiographic data.