Determination of the ore grade of tunnel walls by in situ x-ray fluorescence analysis

A new technique for determining ore grades from tunnel or channel walls by using a portable x-ray fluorescence spectrometer presents an available alternative to the traditional channel-chemical sampling technique. This new technique uses an optimal source-sample distance and a double-beam source probe to measure the ratio of the characteristic to scattered radiation. This differs from the previous method which only measured characteristic energies. In this research, three problems were considered and successfully solved: (1) the matrix effect (an interference effect due to a multi-element matrix); (2) the geometrical effect due to the roughness of the walls; and (3) the effect of uneven mineralization. (author)