Beta backscat­ter method

How does the beta backscatter method work? The functional principle is a simple one: An isotope source emits beta rays - i.e. electrons. These permeate the surface of the coated work piece and initiate an interaction with the atoms in the coating material as well as the base material. The number of returned electrons is measured using a so-called Geiger-Müller tube. This enables precise determination of the coat thickness. However, a prerequisite for successful measurement is that the atomic numbers “Z” of the coating and base material differ by at least 5.