Surface thermometry by laser-induced fluorescence of Dy3+:YAG

Abstract

A novel, non-intrusive, high spatial and temporal resolution thermal imaging system, based on the fluorescence properties of a dysprosium doped yttrium-aluminum-garnet (Dy3+:YAG) thermographic phosphor, has been developed. In this system, the phosphor coating on the test surface is excited by a pulsed Nd:YAG laser. The resulting fluorescent emission of the temperature sensitive 456nm transition and that of the temperature independent 496nm transition, are acquired using a pair of image-intensified charged coupled device cameras. The ratio of the acquired emissions is then correlated to temperature. The Dy:YAG phosphor displays temperature sensitivity in the range of 295-1,350K (with possibility up to 1,800K). Temperature measurements obtained from the surface of a disk heated by an impinging jet, demonstrate the feasibility of this technique for general heat transfer studies involving significant unsteadiness and transient phenomena.