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Yoneda, Yasuhiro; Takeda, Hiroaki*; Tsurumi, Takaaki*
JPS Conference Proceedings (Internet), 1, p.012103_1 - 012103_4, 2014/03
BiWO is the simplest member of the Aurivillius family of (BiO)(ABO) with one oxygen octahedron sandwiched between two BiO layers (m=1). We report the high-energy synchrotron X-ray diffraction study of ferroelectric BiWO at low temperatures, and a new phase transition was found around 200 K. The mechanism of this phase transition was examined by atomic pair-distribution function (PDF) method.
Odaka, Hirokazu*; Ichinohe, Yuto*; Takeda, Shinichiro*; Fukuyama, Taro*; Hagino, Koichi*; Saito, Shinya*; Sato, Tamotsu*; Sato, Goro*; Watanabe, Shin*; Kokubun, Motohide*; et al.
Nuclear Instruments and Methods in Physics Research A, 695, p.179 - 183, 2012/12
Times Cited Count:23 Percentile:84.01(Instruments & Instrumentation)We have developed a new Si/CdTe semiconductor double-sided strip detector (DSD) Compton camera. The camera consists of a 500-m-thick Si-DSD and four layers of 750-m-thick CdTe-DSDs all of which have common electrode configuration segmented into 128 strips on each side with pitches of 250m. In order to realize high angular resolution and to reduce size of the detector system, a stack of DSDs with short stack pitches of 4 mm is utilized to make the camera. Taking advantage of the excellent energy and position resolutions of the semiconductor devices, the camera achieves high angular resolutions of 4.5 degrees at 356 keV and 3.5 degrees at 662 keV. To obtain such high resolutions together with an acceptable detection efficiency, we demonstrate data reduction methods including energy calibration using Compton scattering continuum and depth sensing in the CdTe-DSD. We also discuss imaging capability of the camera and show simultaneous multi-energy imaging.
Takeda, Shinichiro*; Ichinohe, Yuto*; Hagino, Koichi*; Odaka, Hirokazu*; Yuasa, Takayuki*; Ishikawa, Shinnosuke*; Fukuyama, Taro*; Saito, Shinya*; Sato, Tamotsu*; Sato, Goro*; et al.
Physics Procedia, 37, p.859 - 866, 2012/10
Times Cited Count:22 Percentile:98.43(Physics, Applied)By using new Compton camera consisting of silicon double-sided strip detector (Si-DSD) and CdTe-DSD developed for the ASTRO-H mission, an experiment was conducted to study its feasibility for advanced hotspot monitoring. In addition to hotspot imaging already provided by commercial imaging systems, the identification of the variety of radioisotopes is realized thanks to the good energy resolution given by the semiconductor detectors. Three radioisotopes of Ba (356 keV), Na (511 keV) and Cs (662 keV) were individually imaged by applying event selection in the energy window and the -ray images was correctly overlapped by an optical picture. The detection efficiency of 1.6810 (effective area: 1.710 cm) and angular resolution of 3.8 were obtained by stacking five detector modules for 662 keV -ray. The higher detection efficiency required in a specific use can be achieved by stacking more detector modules.
Yoneda, Yasuhiro; Kohara, Shinji*; Takeda, Hiroaki*; Tsurumi, Takaaki*
Japanese Journal of Applied Physics, 51(9), p.09LE06_1 - 09LE06_6, 2012/09
Times Cited Count:14 Percentile:51.32(Physics, Applied)Local structure analysis of BiWO was performed by high-energy X-ray atomic pair-distribution function (PDF) analysis. We found a deviation between local and average structures owing to the different coherence length between BiO and WO layers. Bi atoms were displaced toward the -axis of the orthorhombic structure. The local off-center shift of Bi atoms coupled with thermal factor and negrected in the average structure. The coherence length of BiO layer increased with increasing temperature and splead in the whole crystal when the average structure changed from to structure.
Kajimoto, Ryoichi; Yokoo, Tetsuya*; Nakamura, Mitsutaka; Nakajima, Kenji; Inamura, Yasuhiro; Takahashi, Nobuaki; Maruyama, Ryuji; Soyama, Kazuhiko; Mizuno, Fumio; Shibata, Kaoru; et al.
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no abstracts in English
Kajimoto, Ryoichi; Yokoo, Tetsuya*; Nakamura, Mitsutaka; Nakajima, Kenji; Inamura, Yasuhiro; Takahashi, Nobuaki; Maruyama, Ryuji; Soyama, Kazuhiko; Mizuno, Fumio; Shibata, Kaoru; et al.
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Yoneda, Yasuhiro; Kohara, Shinji*; Han, J. S.*; Takeda, Hiroaki*; Tsurumi, Takaaki*
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BiWO of a bismuth layered compound is expected as non-lead system ferroelectric. The Curie point is in about 1000C. Therefore, it was thought that it became possible to synthesize below the Curie point, and the sample of a single domain was obtained easily in crystal breeding by the flux method and the thin film making by the PLD method. However, a lot of observations not thought about were found with a single domain as for the BiWO crystal actually made. Then, it is a purpose of this experiment to perform high-temperature X-ray diffraction of BiWO, and to verify the phase transition system again. As a result of the experiment, it has been understood that additional structural phase transition exists also below the Curie point. The domain configuration changes by the existence of another phase transition caused during cooling afterwards even if the crystal is promoted below the Curie point at the high temperature.
Takeda, Ayaka*; Nakano, Yuriko*; Ochiai, Asumi*; Yokoo, Hiroki*; Ohara, Yoshiyuki; Fukuyama, Kenjin; Nagayasu, Takaaki; Onuki, Toshihiko*; Utsunomiya, Satoshi*
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Onoe, Hironori; Matsuoka, Toshiyuki; Niwa, Masakazu; Takeda, Takaaki*
no journal, ,
no abstracts in English