Beta backscatter coating thickness gauge
An instrument permitting a quantitative measurement of the thickness of a coating (or a deposit) of a metal (or an alloy) on a different substrate (like silver on brass or copper, or gold on silver...). The principle of the measurement is based on the backscatter phenomenon of beta particles emitted by a sealed radioactive source like promethium 147, srontium-yttrium 90...) and detected by an appropriate detector. Such an instrument can be be hand held or table top one; it is of classical use in jewellery.
jauge d'épaisseur de depôt à rétrodiffusion bêta (Fr.);