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Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.
Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12
Times Cited Count：6 Percentile：51.19(Geosciences, Multidisciplinary)The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.
Al
GaO
scintillators by gamma-ray-induced positron annihilation lifetime spectroscopyFujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Watanabe, Shinta*; Kamada, Kei*; Okano, Yasuaki*; Kato, Masahiro*; Hosaka, Masahito*; et al.
Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08
Times Cited Count：5 Percentile：33.01(Physics, Applied)To clarify the existence of cation vacancies in Ce-doped GdAlGaO (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPAL spectra of GAGG and Ce:GAGG comprised two exponential decay components, which were assigned to positron annihilation at bulk and defect states. By an analogy with Ce:YAl
O, the defect-related component was attributed to Al/Ga-O divacancy complexes. This component was weaker for Ce, Mg:GAGG, which correlated with the suppression of shallow electron traps responsible for phosphorescence. Oxygen vacancies were charge compensators for Al/Ga vacancies. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg
ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.
Shirase, Mitsuyasu*; Abe, Akimasa*; Nago, Makito*; Ishii, Eiichi; Aoyagi, Kazuhei; Wakasugi, Shinichi*
Doboku Gakkai Heisei-29-Nendo Zenkoku Taikai Dai-72-Kai Nenji Gakujutsu Koenkai Koen Gaiyoshu (DVD-ROM), p.1795 - 1796, 2017/09
JAEA has executed the underground facility construction operation from February 2011 to June 2014, while carrying out the maintenance and research project until 2018. This report is about the extra high head pump which was able to drain the high specific gravity grout drainage, which develops during grouting operation at this facility, directly from 250m underground to the surface.
Ijiri, Yuji*; Shindo, Akihisa*; Miura, Hitoshi*; Kamemura, Katsumi*; Tomoe, Naoto*; Nagai, Norihisa*; Abe, Akimasa*; Fujita, Tomoo; Izumi, Atsushi
no journal, ,
no abstracts in English
Kitaura, Mamoru*; Fujimori, Kosuke*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Hirade, Tetsuya; Kamada, Kei*; Watanabe, Shinta*; Onishi, Akimasa*
no journal, ,
Positron annihilation spectroscopy is the only way to investigate the properties of cation vacancies because they are negatively charged. We generated high-energy pulsed gamma rays by the vertical collision of an ultrashort pulse laser and electron beam. In this study, we investigated the vacancy-type defects present in the crystals of GAGG(GdAlGaO), GAGG: Ce and GAGG: Ce, Mg by positron annihilation lifetime spectroscopy using the high-energy gamma rays. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.
AlGaO crystals revealed by gamma-ray induced positron annihilation lifetime spectroscopyFujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Hirade, Tetsuya; Kamada, Kei*; Watanabe, Shinta*; Onishi, Akimasa*
no journal, ,
We generated high-energy pulsed gamma rays by the vertical collision of an ultrashort pulse laser and electron beam. In this study, we investigated the vacancy-type defects present in the crystals of GAGG(GdAlGaO), GAGG: Ce and GAGG: Ce, Mg by positron annihilation lifetime spectroscopy using the high-energy gamma rays. The lifetime of the defect-related component was significantly changed by Mg co-doping. This indicates that the Al/Ga vacancies disappear. This fact corresponds well with the suppression of the phosphorescence component and is an important result showing that the Mg co-doping is effective in suppressing the shallow electron capture center.
