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Journal Articles

Gamma-ray imaging using three-dimensional shadow images created by coded solid

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$$times$$3$$times$$3 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.

Journal Articles

A Phoswich alpha/beta detector for monitoring in the site of Fukushima Daiichi Nuclear Power Station

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 $$^{137}$$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.

Journal Articles

Shield-free directional gamma-ray detector using small-angle Compton scattering

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.

Journal Articles

Simulation study of a shield-free directional gamma-ray detector using Small-Angle Compton Scattering

Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo

Journal of Nuclear Engineering and Radiation Science, 7(4), p.042006_1 - 042006_7, 2021/10

Journal Articles

A Study of directional gamma-ray detector without shield by Monte Carlo simulation

Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo

Proceedings of International Youth Nuclear Congress 2020 (IYNC 2020) (Internet), 4 Pages, 2020/05

Oral presentation

A Development of directional gamma-ray detector without shield

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.

Oral presentation

Investigation of a new gamma-ray imager using small-angle Compton scattering without shield

Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki; Torii, Tatsuo

no journal, , 

no abstracts in English

Oral presentation

Feasibility study on directional gamma-ray detector using small-angle Compton scattering by simulation

Kitayama, Yoshiharu; Terasaka, Yuta; Sato, Yuki

no journal, , 

no abstracts in English

Oral presentation

Car-borne survey and gamma-ray imaging by vehicle-mounted gamma-ray imaging system iRIS-V

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 $$^{137}$$Cs checking source.

Oral presentation

Gamma-ray imaging using three-dimensional shadow images created by coded solids

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Feasibility study on a gamma-ray imaging using three-dimensional shadows of gamma rays

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

no journal, , 

Oral presentation

Study on a new gamma-ray imaging method

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Feasibility study on 4 pi imaging using three-dimensional shadows of gamma rays

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Feasibility study of rhombicuboctahedron directional gamma-ray detectors

Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*; Takada, Eiji*; Torii, Tatsuo*; Ishii, Keizo*

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Experimental feasibility study of an imaging technique using gamma-ray 3D shadows

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Investigation of source location method using multi-point observation data from directional detectors

Hayashi, Hiroko*; Kido, Hiroko*; Kurosawa, Ryohei*; Sone, Koichiro*; Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*; Torii, Tatsuo*

no journal, , 

no abstracts in English

Oral presentation

TlBr polishing & flat panel TlBr detector

Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Fundamental study of multi-isotope imaging using a novel gamma ray imaging technique based on detector response patterns

Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Development of polyhedral type directional gamma-ray detectors

Nogami, Mitsuhiro*; Kitayama, Yoshiharu; Hitomi, Keitaro*; Takada, Eiji*; Torii, Tatsuo*; Ishii, Keizo*

no journal, , 

no abstracts in English

23 (Records 1-20 displayed on this page)