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Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
Japanese Journal of Applied Physics, 63(3), p.032005_1 - 032005_6, 2024/03
Times Cited Count：0 Percentile：0.01(Physics, Applied)We introduce a novel gamma-ray imaging technique that uses detector response patterns. This method employs multiple shielding cubes randomly positioned in a three-dimensional configuration. Within the volume defined by these cubes, a unique gamma-ray flux pattern is formed based on the incidence direction of the gamma rays. This pattern can be measured using the responses of several scintillator cubes. By pre-measuring the detector response pattern and incidence direction of the gamma rays, the incidence direction can be estimated using an unfolding technique. Simulations were performed using a 
Cs point source. Our results show that a 10 MBq Cs source, located 3 m away from the imager, can be imaged with an angular resolution close to 10
. These findings suggest that our new method is comparable to existing gamma-ray imaging techniques. Potential applications of this imaging method include nuclear power plant decommissioning, nuclear medicine, security, and astronomy.
Ishikawa, Takuto*; Matsuo, Mamoru; Kato, Takeo*
Physical Review B, 107(5), p.054426_1 - 054426_9, 2023/02
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
KEK Proceedings 2022-3, p.46 - 53, 2023/01
The position of a streetlight can be predicted from the direction and shape of one's shadow projected on the street at night by the light of the streetlight. The application of this idea to gamma-ray imagers is known as coded aperture. In this study, we proposed the Coded Cube Camera - POrtable (C3PO), which has a three-dimensional shielding and scintillator crystal arrangement, and is composed of lead, scintillator, and depletion cubes randomly arranged in a 3
33 Rurik's cube shape, with each. The output of each scintillator produces a three-dimensional shadow pattern, which is returned to the source direction distribution by unfolding. In this study, we investigated the characteristics and feasibility of the system by simulation using Geant 4.
Schreiber, F.*; Meer, H.*; Schmitt, C.*; Ramos, R.*; Saito, Eiji; Baldrati, L.*; Kl
ui, M.*
Physical Review Applied (Internet), 16(6), p.064023_1 - 064023_9, 2021/12
Times Cited Count：3 Percentile：26.56(Physics, Applied)Oyanagi, Koichi*; Gomez-Perez, J. M.*; Zhang, X.-P.*; Kikkawa, Takashi*; Chen, Y.*; Sagasta, E.*; Chuvilin, A.*; Hueso, L. E.*; Golovach, V. N.*; Sebastian Bergeret, F.*; et al.
Physical Review B, 104(13), p.134428_1 - 134428_14, 2021/10
Times Cited Count：13 Percentile：78.56(Materials Science, Multidisciplinary)
O
/YIG structureQi, J.*; Hou, D.*; Chen, Y.*; Saito, Eiji; Jin, X.*
Journal of Magnetism and Magnetic Materials, 534, p.167980_1 - 167980_6, 2021/09
Times Cited Count：1 Percentile：7.51(Materials Science, Multidisciplinary)Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
Physical Review Research (Internet), 3(2), p.023219_1 - 023219_15, 2021/06
We theoretically propose the long-range spin transport mediated by the gapless surface states of topological Dirac semimetal (TDSM). Low-dissipation spin current is a building block of next-generation spintronics devices. While conduction electrons in metals and spin waves in ferromagnetic insulators (FMIs) are the major carriers of spin current, their propagation length is inevitably limited due to the Joule heating or the Gilbert damping. In order to suppress dissipation and realize long-range spin transport, we here make use of the spin-helical surface states of TDSMs, such as CdAs and NaBi, which are robust against disorder. Based on a junction of two FMIs connected by a TDSM, we demonstrate that the magnetization dynamics in one FMI induces a spin current on the TDSM surface flowing to the other FMI. By both the analytical transport theory on the surface and the numerical simulation of real-time evolution in the bulk, we find that the induced spin current takes a universal semi-quantized value that is insensitive to the microscopic coupling structure between the FMI and the TDSM. We show that this surface spin current is robust against disorder over a long range, which indicates that the TDSM surface serves as a promising system for realizing spintronics devices.
Baldrati, L.*; Schmitt, C.*; Gomonay, O.*; Lebrun, R.*; Ramos, R.*; Saito, Eiji; Sinova, J.*; Klui, M.*
Physical Review Letters, 125(7), p.077201_1 - 077201_6, 2020/08
Times Cited Count：36 Percentile：91.52(Physics, Multidisciplinary)Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
Physical Review Research (Internet), 2(2), p.023195_1 - 023195_11, 2020/05
Hou, D.*; Qiu, Z.*; Saito, Eiji
NPG Asia Materials, 11, p.35_1 - 35_6, 2019/07
Times Cited Count：40 Percentile：84.4(Materials Science, Multidisciplinary)
-FeO/NiO/Pt epitaxial stacksDong, B.-W.*; Baldrati, L.*; Schneider, C.*; Niizeki, Tomohiko*; Ramos, R.*; Ross, A.*; Cramer, J.*; Saito, Eiji; Klui, M.*
Applied Physics Letters, 114(10), p.102405_1 - 102405_5, 2019/03
Times Cited Count：11 Percentile：52.56(Physics, Applied)Maki, Akira; ; Taguchi, Katsuya; ; Shimizu, Ryo; Shoji, Kenji;
JNC TN8410 2001-012, 185 Pages, 2001/04
JNC-TN8410-2001-012.pdf:9.61MB
"The third technological meeting of Tokai Reprocessing plant (TRP)" was held in JNFL Rokkasyo site on March 14
, 2001. The technical meetings have been held in the past two times. The first one was about the present status and future plan of the TRP and second one was about safety evaluation work on the TRP. At this time, the meeting focussed on the corrosion experrience, in-service inspection technology and future maintenance plan. The report contains the proceedings, transparancies and questionnaires of the meeting are contained.
Usami, Hiroshi; Morishita, Yuki; Torii, Tatsuo; Sugita, Takeshi*; Kobayashi, Ikuo*
no journal, ,
no abstracts in English
Araki, Yasufumi
no journal, ,
Araki, Yasufumi
no journal, ,
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo
no journal, ,
To ensure the safety of workers working at the Fukushima Daiichi Nuclear Power Station (FDNPS), a technology to measure the distribution of radioactive materials in the working environment is required. In order to develop a new gamma-ray imager that can compensate for the shortcomings of existing gamma-ray imagers, the feasibility of a gamma-ray detector that does not require a shield was examined by simulation. There are pinhole cameras and a Compton camera as a technology for imaging radioactive material distribution. Since the pinhole camera can identify the source direction in one event, the image reconstruction is easy, and there is a possibility that it can be applied to quantitative measurement. However, the total weight is too heavy to be suitable for remote measurement because a shield is required. Since the Compton camera does not require a shield, it is small and light, and remote measurement is possible. However, multiple events are required to estimate the source direction, and the cone drawn at that time becomes noise, and the S/N ratio of the image is lowered. We propose a novel gamma-ray imager such as a pinhole camera that does not require shields. In this study, we verified the principle of a directional gamma-ray detector that does not require a shield.
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
