Application of Ag-Doped Phosphate Glasses as Etched Nuclear Track Detectors

Introduction: The Ag-doped phosphate glasses are commonly employed as the personal dosimeter based on the radio photoluminescence detection. It is well-known that phosphate glass is suitable glass type for the nuclear track detectors such as BP-1 and VG-13. Glass nuclear track detectors can register a latent track even in vacuum. Therefore, it is able to use under the strict environments such as temperature and vacuum in space because of its excellent stability. BP-1 is a successful detector to observe ultra-heavy cosmic rays. However, it is very difficult to get it because BP-1 is not a commercial product. Moreover, in our study, it was found that the quality control is very difficult for the mass production. In this study, we challenged the utilization of Ag-doped phosphate glass as a nuclear track detector, which is commercial and mass product for personal dosimeter. We introduce the ability and possibility of this glass.\nExperimental: The Ag-doped phosphate glass (51.2wt%O, 31.6wt%P, 11.0wt%Na, 6.1wt%Al, 0.2wt%Ag) with size of 8.5 mm x 8.5mm x 1.5mm , AGC Techno Glass Co. Ltd., Japan, was employed. The chemical etching with NaOH solution varying its normality (0.5 N – 12 N) was applied for verifying etching condition. Detectors were irradiated to Xe ion beams with energies below 290 MeV/n, covering Z/beta range of 90 - 130, at HIMAC (Heavy Ion Medical Accelerator in Chiba) of NIRS, Japan. The exposed density was ~ 3,000 ions/cm2 for each detector. After the etching, the diameter of etch pit formed in glass was automatically measured and analyzed with a high-speed imaging microscope system (HSP-1000, SEIKO Precision Inc., Japan). The track registration sensitivity was determined as a function of Z/beta.\nResults and Discussion: The glass was linearly etched with NaOH solutions as a function of etching time. The bulk etching velocity was found to be extremely faster (~40 times) than CR-39 plastic nuclear track detectors. A unique tendency that the bulk etching velocity shows a maximum peak around 2N of the normality of NaOH was observed. This is quite different from the hydrolysis process in the CR-39 polymer. It implies the different etching mechanism in glass due to the interaction of alkaline OH- and acid oxide (PO3). The etch pits of Xe ions were successfully formed in glass as shown in Fig. 1. The surface condition of the glass after the etching is quite clear and also the shape of formed etch pit is extremely fine compared with the etch pit in other conventional materials including even CR-39. The track response as a function of Z/beta showed the extremely steep function and high sensitivity comparable with BP-1 glass detectors. The Ag-doped phosphate glass will be applicable to the precise observation of ultra-heavy cosmic rays for resolving the still unknown puzzle about galactic material source and its evolution in the galaxy.17th International Conference on Solid State Dosimetr