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Your search keyword '"Yokota, Yuui"' showing total 1,039 results
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1,039 results on '"Yokota, Yuui"'

2. Shape-controlled crystal growth of Y$_3$Al$_5$O$_{12}$:Ce single crystals with application of micro-pulling-down method and Mo crucibles, and their scintillation properties

Author

Yoshino, Masao, Kotaki, Atsushi, Yokota, Yuui, Horiai, Takahiko, and Yoshikawa, Akira

Subjects
Condensed Matter - Materials Science, Physics - Instrumentation and Detectors, Physics - Optics
Abstract

The technology to grow single crystals of the required shape directly from a melt has been researched extensively and developed in various industries and research fields. In this study, a micro-pulling-down method and a Mo crucible were applied to the shape-controlled crystal growth of Y$_3$Al$_5$O$_{12}$:Ce (YAG:Ce). Three types of Mo crucibles with different die shapes were developed. Stable crystal growth in the same shape as the die was achieved, and scintillation properties that are comparable with those of the previously reported YAG:Ce were obtained., Comment: 15 pages, 8 figures, submitted to Journal of Crystal Growth

Published
2021

3. Temperature dependence and quenching characteristics of (La, Gd)$_2$Si$_2$O$_7$ scintillators at various Ce concentrations

Author

Yoshino, Masao, Horiai, Takahiko, Takasugi, Tatsuki, Jary, Vitezslav, Nikl, Martin, Yokota, Yuui, Kamada, Kei, Shoji, Yasuhiro, Kucerkova, Romana, and Yoshikawa, Akira

Subjects
Condensed Matter - Materials Science, Physics - Instrumentation and Detectors, Physics - Optics
Abstract

We investigated the thermal stability of scintillation and the luminescence performances of (La, Gd)${}_{2}$Si${}_{2}$O${}_{7}$ single crystals at various Ce concentrations. We prepared (La${}_{0.25-x}$, Ce${}_{x}$, Gd${}_{0.75}$)${}_{2}$Si${}_{2}$O${}_{7}$ (x = 0.0001, 0.001, 0.005, 0.01, 0.02, 0.05, and 0.1; unit: molar concentration) single crystals by the Czochralski and micro-pulling-down methods. With increasing Ce concentration, the photoluminescence emission and photoluminescence excitation spectral bands shifted to low energies and the activation energy $\mathrm{\Delta }E$ for thermal quenching decreased. For Ce $\mathrm{<}$ 0.5 at.% samples, the photoluminescence emission background value calculated in the exponential approximation started to increase at temperatures greater than 320 K, which is probably because of Ce${}^{3+}$ 5$\textit{d}$ excited-state ionization. However, the effect was weaker for the Ce $\ge $ 0.5% samples, which may indicate a comparatively larger contribution from other nonradiative relaxations. Thus the main reason for the thermal quenching of the Ce${}^{3+}$ emission in (La, Gd)${}_{2}$Si${}_{2}$O${}_{7}$ is the combination of the 5$\textit{d}$1 excited-state ionization and nonradiative relaxation via thermally excited crossover from the 5$\textit{d}$ excited state to the 4$\textit{f}$ ground state. The temperature dependence of the scintillation light yield was similar irrespective of the Ce concentration, with Ce 1.0% exhibiting the best performance within the temperature range 300 K to 450 K., Comment: 27 pages, 11 figures

Published
2021

9. Crystal growth and optical properties of Ce-doped (La,Y)$_2$Si$_2$O$_7$ single crystal

Author

Horiai, Takahiko, Paterek, Juraj, Pejchal, Jan, Jarosova, Marketa, Rohlicek, Jan, Kurosawa, Shunsuke, Hanada, Takashi, Yoshino, Masao, Yamaji, Akihiro, Toyoda, Satoshi, Sato, Hiroki, Ohashi, Yuji, Kamada, Kei, Yokota, Yuui, Yoshikawa, Akira, and Nikl, Martin

Subjects
Physics - Optics, Condensed Matter - Materials Science
Abstract

We have grown Ce-doped (La,Y)$_2$Si$_2$O$_7$ single crystal by micro-pulling-down method and investigated its optical and scintillation properties. We have successfully prepared the single crystal with (Ce$_{0.015}$La$_{0.600}$Y$_{0.385}$)$_2$Si$_2$O$_7$ composition. The observed thermal quenching process could be characterized by the quenching temperature (T50%) of 526 K and its activation energy was determined to be 0.62 eV. Further considering the thermal quenching factors, it was found that the thermal quenching was caused by at least the thermal ionization and maybe also by classical thermal quenching. The light output and scintillation decay time were evaluated to be ~12,000 photons/MeV and ~42 ns, respectively. These results indicate that (Ce$_{0.015}$La$_{0.600}$Y$_{0.385}$)$_2$Si$_2$O$_7$ has a great potential for application in scintillation materials.

Published
2021
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21. Development of a three-dimensional-micro-pulling-down method and growth of spring-shaped sapphire single crystals.

Author

Yokota, Yuui, Ohashi, Yuji, and Yoshikawa, Akira

Subjects
*SINGLE crystals, *SAPPHIRES, *CRUCIBLES, *CRYSTALS, *CRYSTALLINITY
Abstract

A three-dimensional-micro-pulling-down (3D-μ-PD) method was developed for the growth of 3D shaped single crystals, and spring-shaped sapphire single crystals were grown by the 3D-μ-PD method using Mo crucibles with different dies. The shape of the die significantly affected the growth stability and shape control of the spring-shaped single crystals. Spring-shaped sapphire single crystals with a smaller helical pitch and larger helical radius were obtained easily using a Mo crucible with a sharp conical die compared to that with a blunt conical die. However, spring-shaped sapphire single crystals grown using a Mo crucible with an inverse conical die can be obtained with smaller helical pitches, and the shape of the cross-sectional plane is a horizontally extended elliptical shape. The difference in the shape of the cross-sectional plane for spring-shaped sapphire single crystals affects the crystallinity and mechanical properties. Furthermore, crystals grown using the Mo crucible with the inverse conical die exhibited a larger shrinkage rate in the compression test. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Crystal growth, luminescence, and scintillation properties of Er-doped La2Hf2O7 single crystal

Author

Hayashi, Naomoto, primary, Yokota, Yuui, additional, Horiai, Takahiko, additional, Yamanoi, Kohei, additional, Yoshino, Masao, additional, Yamaji, Akihiro, additional, Murakami, Rikito, additional, Hanada, Takashi, additional, Sato, Hiroki, additional, Ohashi, Yuji, additional, Kurosawa, Shunsuke, additional, Kamada, Kei, additional, Sarukura, Nobuhiko, additional, and Yoshikawa, Akira, additional

Published
2024
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32. Fabrication and Properties for Thermal Neutron Detection of 6LiCl/Rb2CeCl5 Eutectic Scintillator

Author

Sasaki, Rei, primary, Kamada, Kei, additional, Yoshino, Masao, additional, Kim, Kyoung Jin, additional, Murakami, Rikito, additional, Horiai, Takahiko, additional, Yamaji, Akihiro, additional, Kurosawa, Shunsuke, additional, Yokota, Yuui, additional, Sato, Hiroki, additional, Ohashi, Yuji, additional, Hanada, Takashi, additional, and Yoshikawa, Akira, additional

Published
2024
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33. Growth of Mg2Si thermoelectric eutectics by unidirectional solidification

Author

Hayashi, Naomoto, primary, Yokota, Yuui, additional, Horiai, Takahiko, additional, Yoshino, Masao, additional, Yamaji, Akihiro, additional, Murakami, Rikito, additional, Hanada, Takashi, additional, Sato, Hiroki, additional, Ohashi, Yuji, additional, Kurosawa, Shunsuke, additional, Kamada, Kei, additional, and Yoshikawa, Akira, additional

Published
2023
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40. Fabrication and Properties for Thermal Neutron Detection of 6 LiCl/Rb 2 CeCl 5 Eutectic Scintillator.

Author

Sasaki, Rei, Kamada, Kei, Yoshino, Masao, Kim, Kyoung Jin, Murakami, Rikito, Horiai, Takahiko, Yamaji, Akihiro, Kurosawa, Shunsuke, Yokota, Yuui, Sato, Hiroki, Ohashi, Yuji, Hanada, Takashi, and Yoshikawa, Akira

Subjects
NEUTRON counters, THERMAL neutrons, SCINTILLATORS, THERMAL properties, EUTECTICS, NEUTRON capture, LITHIUM chloride, CATHODOLUMINESCENCE
Abstract

The 3He gas is commonly used for the detection of thermal neutrons. However, with the depletion of 3He gas, there is a need to develop new solid scintillators for thermal neutron detection. Solid scintillators containing 6Li, which have large neutron capture cross-sections and a large amount of energy released by transmutation reactions, are commonly used as alternative candidates. However, only single-crystal scintillators are currently used, and their 6Li concentration is limited by their chemical composition. In this study, we designed, grew, and evaluated a new eutectic scintillator, Rb2CeCl5/LiCl, which can improve the 6Li concentration compared with single-crystal scintillators. Rb2CeCl5, which was selected as the scintillator phase, has excellent scintillator properties (light yield: 36,000 photons/MeV, decay time: mostly 24 ns, slightly 153 ns), and is less deliquescent than other halide scintillators. The crystal grown using the vertical Bridgman method exhibited a eutectic phase composed of Rb2CeCl5 and LiCl. The eutectic crystals exhibited Ce3+ 5d-4f emissions, with a peak between 360 and 370 nm. The Rb2CeCl5 phase was identified as the luminescent phase via cathodoluminescence mapping, and 16,000 photons/neutron of the light yield and 56.1 ns of the decay time were observed. This study indicates that the Rb2CeCl5/LiCl eutectic scintillator is a promising candidate for use in thermal neutron detectors. [ABSTRACT FROM AUTHOR]

Published
2024
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