Radiation resistance of praseodymium-doped aluminum lithium fluorophosphate scintillator glasses for laser fusion experiments

We report the gamma (γ)-ray radiation resistance of praseodymium (Pr3+)-doped aluminum lithium fluorophosphate scintillator glasses. For its assessment as a scintillator material for laser fusion experiments, a 20Al(PO3)3-80LiF-PrF3 (Pr3+-doped APLF) glass was irradiated with γ-rays from a cobalt-60 (60Co) source resulting in an absorbed dose of 5.2 kGy. Although γ-ray-irradiation results in increased absorption due to phosphorus-oxygen hole centers (POHCs) and PO32− electron centers (PO3 ECs), these radiation-induced defects do not modify the glass emission as both non-irradiated and γ-ray-irradiated glasses exhibit similar emission spectra and decay times under optical and X-ray excitation. The emission peaks observed also correspond to the different interconfigurational 4f5d → 4f2 and intraconfigurational 4f2 transitions of Pr3+ ions which are neither oxidized nor reduced by irradiation. Our results show that Pr3+-doped APLF glass still maintains its characteristic fast decay time and that γ-ray irradiation does not affect the glass scintillation mechanisms.Shinohara K., Empizo M.J.F., Cadatal-Raduban M., et al. Radiation resistance of praseodymium-doped aluminum lithium fluorophosphate scintillator glasses for laser fusion experiments. Japanese Journal of Applied Physics 62, 010613 (2023); https://doi.org/10.35848/1347-4065/aca0d4

Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.Iwano K., Yamanoi K., Iwasa Y., et al. Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors. AIP Advances 6, 105108 (2016); https://doi.org/10.1063/1.4965927

科学技術評価のための包括的分析基盤の構築 : 国際戦略編

一般講演要

Photoluminescence and enhanced photocatalytic activity of mechanically activated graphite-zinc oxide composites

In this work, we show evidence of enhanced photocatalytic activity in mechanically activated graphite-zinc oxide (ZnO) composites using time-resolved photoluminescence (TRPL) and time-integrated photoluminescence (TIPL) spectroscopy. The graphite-ZnO composites were synthesized through facile mixing and grinding of graphite and ZnO precursors without any heat treatment. The precursors were ground at room temperature with varying graphite to ZnO mass ratios of 3:1, 2:2, and 1:3 for 0, 2, and 4 h. Raman spectroscopy and x-ray diffractometry confirm the presence of both graphite and ZnO and corroborate the graphite-to-ZnO ratio. XRD results also show a hexagonal wurtzite ZnO crystal structure. To determine the photocatalytic activity of the composites, the degradation of methylene blue (MB) under UV light was measured with a UV–vis spectrophotometer. Nearly full degradation was achieved within a half hour for all composite samples. The kinetic rates of 0.10 min ^−1 were also estimated for mixed and unground samples and samples ground for 2 h. Time-resolved photoluminescence (TRPL) and time-integrated photoluminescence (TIPL) spectroscopy reveal longer lifetimes and more intense UV emissions, respectively, for composite samples compared to pure ZnO. We propose that the even agglomeration of zinc oxide particles on graphite due to grinding enhances the photocatalytic degradation by the zinc oxide. TRPL and TIPL spectroscopy implies the excellent binding between ZnO and graphite, which greatly contributes to the decreased charge recombination resulting in the superior photocatalytic activity observed with our samples

Spectroscopic investigation of praseodymium and cerium co-doped 20Al(PO3)3-80LiF glass for potential scintillator applications

International audienceThe optical properties of 20Al(PO3)3–80LiF (APLF80) glass co-doped with praseodymium (Pr3+) and cerium (Ce3+) ions are explored. By co-doping the host APLF80 glass matrix with praseodymium (Pr3+) and cerium (Ce3+) ions (APLF80 + PrCe), improvement in the luminescence decay time of the 5d → 4f allowed electric dipole transition of singly-doped APLF80 + Pr under optical excitation is achieved. Both radiative and non-radiative energy transfers from Pr3+ to Ce3+ are observed. Non-radiative energy transfer leads to Pr3+ luminescence quenching resulting to faster decay times of Pr3+, especially at high Ce3+-doping concentrations. Our results present exciting prospects for APLF80 as a response time improved scintillator

Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium