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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 333 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.
Morishita, Yuki; Takasaki, Koji; Kitayama, Yoshiharu; Tagawa, Akihiro; Shibata, Takuya; Hoshi, Katsuya; Kaneko, Junichi*; Higuchi, Mikio*; Oura, Masatoshi*
Radiation Measurements, 160, p.106896_1 - 106896_10, 2023/01
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)This study proposes a newly developed phoswich alpha/beta detector that can discriminate alpha and beta particles emitted from the alpha and beta contaminations in the FDNPS site. The phoswich alpha/beta detector is made up of two layers of scintillators that detect alpha and beta particles. The pulse shape discrimination (PSD) method was used to detect alpha particles in high beta particle and high gamma-ray (comparable to gamma-ray dose rate near the FDNPS reactor building) environments. Due to a 23.3% full width at half maximum (FWHM) energy resolution for alpha particles, the detector can be used to distinguish between nuclear fuel materials such as plutonium and its radon progeny (Po-214). Moreover, the detector could distinguish alpha particles from Cs gamma rays with a dose rate background up to 9.0 mSv/h. It is the first to demonstrate that the developed phoswich detector can be used to discriminate and measure alpha and beta particles of the actual contaminated FDNPS samples.
Kitayama, Yoshiharu
Gamma Ray Imaging; Technology and Applications, p.165 - 179, 2023/00
A gamma-ray imager is a powerful tool for visualizing the distribution of radioactive materials. Recently, it has been applied to the decommissioning site of the Fukushima Daiichi Nuclear Power Station. At the decommissioning site, an imager compact, lightweight, and capable of quantitative evaluation of radioactivity is demanded. The Gamma-ray Imager using Small-Angle Scattering (GISAS) was proposed as a gamma-ray imager that meets all these requirements. GISAS consists of several shield-free directional gamma-ray detectors that detect only small-angle Compton scattering. Simulations and experiments verified the feasibility of the shield-free directional gamma-ray detectors. The shield-free directional gamma-ray detector consists of a scatterer that detects small-angle Compton scattering and an absorber that detects the scattered gamma rays. By setting an appropriate energy window for each detector, only scattering events that can be considered almost straightforward are detected. Through simulations and experiments, we have confirmed that using a silicon drift detector as the scatterer and a Gd3Al2Ga3O12 scintillator as the absorber, we can detect only small-angle Compton scattering events and obtain directionality for 662 keV gamma rays.
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo
Journal of Nuclear Engineering and Radiation Science, 7(4), p.042006_1 - 042006_7, 2021/10
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo
Proceedings of International Youth Nuclear Congress 2020 (IYNC 2020) (Internet), 4 Pages, 2020/05
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.
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo
no journal, ,
no abstracts in English
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki
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no abstracts in English
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki
no journal, ,
We have developed a vehicle-mounted gamma-ray imaging system, iRIS-V. This system is capable of gamma-ray imaging around the vehicle and a car-borne survey similar to that of a monitoring car. This presentation will report the results of a car-borne survey of Route 35 in the difficult-to-return zone by iRIS-V and a gamma-ray imaging test around the entire vehicle using a Cs checking source.
Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
no abstracts in English
Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
no abstracts in English
Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
no abstracts in English
Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*; Takada, Eiji*; Torii, Tatsuo*; Ishii, Keizo*
no journal, ,
no abstracts in English
Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki
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Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
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no abstracts in English
Hayashi, Hiroko*; Kido, Hiroko*; Kurosawa, Ryohei*; Sone, Koichiro*; Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*; Torii, Tatsuo*
no journal, ,
no abstracts in English
Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*
no journal, ,
no abstracts in English
Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
no abstracts in English
Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*; Takada, Eiji*; Torii, Tatsuo*; Ishii, Keizo*
no journal, ,
no abstracts in English