Development of a method for distinguishing alpha particles from other types of radiation using a high-resolution alpha imager

Morishita, Yuki; Sagawa, Naoki; Fujisawa, Makoto; Kurosawa, Shunsuke*; Sasano, Makoto*; Hayashi, Masateru*; Tanaka, Hiroki*

Radiation Measurements, 181, p.107371_1 - 107371_5, 2025/02

https://doi.org/10.1016/j.radmeas.2024.107371

The effects of different types of radiation on a high-resolution alpha imager developed using an electron multiplying charge-coupled device (EMCCD) camera were investigated. This imager was originally developed to visualize alpha particles from Pu oxide particles at decommissioning sites. Other types of radiation such as beta particles, gamma rays, and neutrons are also present. The purpose of this study is to investigate the effects of these background radiations on the imager and to develop a method to discriminate between alpha particles and other types of radiation. When measuring gamma rays, and neutrons, the sensor of the EMCCD camera generated high intensity signals due to gamma rays and neutrons. These radiations were identified by image processing. The image values were binarized and the findContours function was applied to count the number of alpha particle spots. The results showed that alpha and gamma (neutron) radiation can be discriminated by using differences in intensity. This method will be useful for visualizing alpha particles at decommissioning sites.

Eddy current-adjusted plasma shape reconstruction by Cauchy condition surface method on QUEST

Nakamura, Kazuo*; Jiang, Y.*; Liu, X.*; Mitarai, Osamu*; Kurihara, Kenichi; Kawamata, Yoichi; Sueoka, Michiharu; Hasegawa, Makoto*; Tokunaga, Kazutoshi*; Zushi, Hideki*; et al.

Fusion Engineering and Design, 86(6-8), p.1080 - 1084, 2011/10

https://doi.org/10.1016/j.fusengdes.2011.04.045

A Conceptual design of a negative-ion-grounded advanced tokamak reactor; NAVIGATOR(FER)

Yamamoto, Shin; Ohara, Yoshihiro; Tani, Keiji; Nishio, Satoshi; Okumura, Yoshikazu; Araki, Masanori; Azumi, Masafumi; R.S.Devoto*; Fujisawa, Noboru; Hitoki, Shigehisa*; et al.

JAERI-M 88-086, 183 Pages, 1988/05

JAERI-M-88-086.pdf:4.57MB

no abstracts in English

Development of discrimination method of alpha particles and other radiations by alpha particle imaging detector using a CCD camera

Morishita, Yuki; Sagawa, Naoki; Fujisawa, Makoto; Kurosawa, Shunsuke*; Sasano, Makoto*; Hayashi, Masateru*; Tanaka, Hiroki*

no journal, , 

This study reports the effects of different types of radiation on a high-resolution alpha imager, developed using an Electron Multiplying Charge-Coupled Device (EMCCD) camera. The imager was originally designed to visualize Pu oxide particles in decommissioning sites, where other types of radiation such as beta particles, gamma-rays, and neutrons are also present. The measurement of alpha particles, beta particles, gamma-rays, and neutrons were performed, and it was found that the EMCCD camera's sensor detected gamma-rays and neutrons. The discrimination method was based on the characteristics of the image distribution, where the image values were binarized and a Gaussian filter was applied to count the number of alpha particle spots. The results show that it is possible to discriminate between alpha and gamma (neutron) rays using the difference in intensity. The study provides important information for the development of radiation detection techniques in decommissioning sites.

Improvement of the decontamination detergents and methods for body radioactive contamination, 2; Evaluation of residual locations after decontamination and spread of contamination by dequiping of protective equipments

Fujisawa, Makoto; Tomioka, Akifumi; Izaki, Kenji; Shioya, Satoshi

no journal, , 

It is important to predict the spread of radioactive materials attached to workers' bodies. We evaluated the degree to which contamination remained after wiping off protective gear and the degree to which contamination was dispersed when it was removed. In the test, we applied fluorescent paint that simulates radioactive substances to protective gear, wiped it off with a wet rag, and removed the gear. And we photographed the fluorescent paint with a camera and evaluated the decontamination effect of wiping and the spread of simulated contamination. As a result of the test, we were able to evaluate the degree to which the protective gear was contaminated.

Measurement of mixed samples of alpha and beta (gamma) nuclides using a high spatial resolution alpha-particle imager with Quantitative CMOS camera

Fujisawa, Makoto; Morishita, Yuki; Sagawa, Naoki; Kurosawa, Shunsuke*; Sasano, Makoto*; Hayashi, Masateru*

no journal, , 

The measurement of alpha contamination, or alpha radiation, is important for the decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS). It is very important to verify whether alpha particles can be visualized in a situation where alpha, beta, gamma-rays are mixed together. In this study, we applied our newly developed alpha imager to the measurement of actual samples containing a mixture of alpha, beta, and gamma nuclides, and verified its effectiveness. The alpha imager consisted of a qCMOS camera (ORCA-Quest (C15550-20UP)) and an optical microscope (BX53MRF-S from Olympus). A ZnS(Ag) scintillator with a thickness of 3.25 mg/cm was used for alpha measurements by placing the scintillator closely over a sample. An Am alpha standard source was measured to verify whether alpha particles could be measured. In addition, samples containing a mixture of alpha, beta, and gamma nuclides were measured. Image processing was used to extract clusters of alpha particles. By applying image processing, clusters of alpha particles were successfully extracted. When measuring a sample with a mixture of alpha, beta, and gamma nuclides, clusters of alpha particles could be confirmed. Although the sample had a higher beta activity than alpha activity, only alpha particles were successfully extracted. The developed alpha imager will be useful for contamination measurement in the site of FDNPS.

Improvement of the decontamination detergents and methods for body radioactive contamination, 1; Evaluation of skin decontamination effects using various commercial detergents and methods

Tomioka, Akifumi; Fujisawa, Makoto; Izaki, Kenji; Shioya, Satoshi

no journal, , 

When body contamination occurs, decontamination is carried out basically by wiping with wet paper rag, pouring large amounts of running water, and using detergents such as neutral detergents. However, it can be said that these methods do not reflect much of the technological progress to date. For example, we believe that more efficient body decontamination can be achieved by applying new technologies of the beauty care and health care field. In this study, we evaluated the decontamination effects of multiple commercially available detergents and microbubble showers that are expected to have decontamination effects, through tests using a particulate visualization system and tests using radioactive substances.

Spin dynamics of the quasi-one-dimensional antiferromagnet CuClHCSO

Fujisawa, Masashi*; Shiraki, Kosuke*; Okubo, Susumu*; Ota, Hitoshi*; Yoshida, Makoto*; Tanaka, Hidekazu*; Sakai, Toru

no journal, , 

The spin dynamics of the quasi-one-dimensional antiferromagnet CuClHCSO was investigated by the electron spin resonance (ESR). The system has a spin gap, but the direct ESR transition of the spin gap is forbidden due to the spin conservation law, because the spin gap is an energy gap between the singlet and triplet states. However, the direct ESR transition of the spin gap was observed for this material. The present study revealed that the origin of the direct ESR transition is the Dzyaloshinsky-Moriya interaction, and applying the selection rule of the angle-dependent ESR intensity, we successfully specified the direction of the interaction vector.

Observable counting rate limits of radiation detectors used in stack monitors

Imahashi, Atsushi; Hosomi, Kenji; Fujisawa, Makoto; Takada, Chie

no journal, , 

no abstracts in English