Optically stimulated luminescence in RE-doped LuAG crystals

Optically stimulated luminescence (OSL) technique is being extensively employed to assess the delivered dose in different applications, in particular dating and dosimetry. The dating of geological sediments, for example, relies on the luminescence properties of quartz and feldspars. Over the geological era, the exposure of buried quartz grains to natural radioactivity results in charges trapped in localized defects. Since some of these trapped electrons can be released by exposure to blue light producing an UV emission, it is possible to estimate the dose delivered to the sample (and the time elapsed) since its last exposure to sunlight (i.e. the burial time) using the OSL technique [1]. The same physical process is also exploited in radiation dosimetry applications using synthetic crystals commercially available (e.g. Al2O3:C) [2] and has been proposed for real time dose measurements when coupled to radioluminescence (RL) signal [3]. In this work, we describe the recently discovered OSL properties of rare earth doped Lu3Al5O12 crystals (LuAG:RE). We found, in fact, that a trap responsible for an intense peak detected with thermally stimulated luminescence (TSL), can be significantly depleted by exposure to white light. We will present a detailed characterization of OSL in LuAG showing the experimental evidences of the phenomenon. We investigated its properties to evaluate the feasibility of using this material as a dosimeter for various applications. In particular, we determined the trap parameters of the optically bleachable defect, its bleaching efficiency as a function of stimulation wavelength, the OSL emission spectrum, etc. Several samples with different growing conditions (RE-doping, co-doping, post growth annealing, etc.) have been considered. Moreover, our investigation aimed at the identification of the point defect responsible for the dosimetric traps. This would possibly allow the engineering of the material resulting in improved performances of the dosimeter. The state of the art of our investigation will be presented.