On-belt analysis of minerals using naturally occurring gamma radiation

We describe a method to analyze materials on a conveyor belt using natural gamma spectra collected with a BGO (bismuth germanate) gamma ray detector, which collects emissions from potassium (K), uranium (U), and thorium (Th) in the materials. A statistical model is proposed based on a Poisson process and an approximate maximum likelihood (ML) technique via the expectation-maximization (EM) algorithm is then used to estimate the amount of each of the three elements in the material. A refinement of the statistical model is used to estimate linear drift in the detector.