Novel radio-photoluminescence materials and applications

Abstract

Radio-photoluminescence (RPL) is a phenomenon whereby a new luminescent centre is generated in a material by the interaction of an ionizing radiation with the medium. Despite the usefulness of RPL, e.g. in radiation measurements, there are only a limited number of RPL materials available today, which limits our understanding of the phenomenon as well as extending its use for new applications. In recent investigations, a large number of new RPL material systems have been proposed for radiation measurements. In particular, Sm-based RPL is one of the most intensively studied alternative systems, which shows RPL properties owing to the intravalence reduction of the Sm ion (Sm³⁺ → Sm²⁺) induced by ionizing radiation. The generated Sm²⁺, as well as Sm³⁺, acts as a luminescent centre and shows photoluminescence, typically around 700 nm. This approach has enabled us to explore a wider range of material choices and to find a new application of RPL. An example is microbeam radiation therapy (MRT), which requires the measurement of extremely large radiation dose distributions at a microscopic scale. Such a new class of RPL is not only limited to Sm-based materials but also to those doped with other rare earth ions (e.g., Eu and Yb) and undoped materials.