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Yasuda, Hiroshi*; Yajima, Kazuaki*; Sato, Tatsuhiko
Radiation Measurements, 134, p.106309_1 - 106309_4, 2020/06
Times Cited Count：8 Percentile：60.71(Nuclear Science & Technology)We have investigated an application of a recently developed electronic personal dosimeter (D-Shuttle) for aviation dosimetry. As results of measurements in four long-haul flights between Japan and Germany, the D-Shuttle indicated values were in the range of 25 to 30% of the total H
(10) values estimated by a route-dose calculations program JISCARD EX. Though we need more measurements and analyses under different flight conditions to conclude, according to these results obtained so far, it would be possible to perform monitoring of the annual aviation doses of frequent flyers by using D-Shuttle on an individual basis.
Hoshi, Katsuya; Tsujimura, Norio; Yoshida, Tadayoshi; Kurihara, Osamu*; Kim, E.*; Yajima, Kazuaki*
Progress in Nuclear Science and Technology (Internet), 6, p.152 - 155, 2019/01
Yasuda, Hiroshi*; Yajima, Kazuaki*; Takada, Masashi*; Sato, Tatsuhiko; Nakamura, Takashi*
Progress in Nuclear Science and Technology (Internet), 1, p.356 - 359, 2011/02
It was verified that CREPAS can successfully measure cosmic-ray energetic neutrons (
10 MeV) separately from other components.
Takada, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*; Sato, Tatsuhiko; Nakamura, Takashi*
Radiation Measurements, 45(10), p.1297 - 1300, 2010/12
Times Cited Count：3 Percentile：24.08(Nuclear Science & Technology)In this study, we carried the phoswich-typed neutron detector on the business jet, and measured neutron energy spectrum above Japan.
Takada, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*; Sato, Tatsuhiko; Nakamura, Takashi*
Journal of Nuclear Science and Technology, 47(10), p.932 - 944, 2010/10
Times Cited Count：7 Percentile：45.04(Nuclear Science & Technology)Neutron energy spectrum from 7 to 180 MeV and photon energy spectrum from 3.5 to 42 MeV were measured on board an aircraft using a newly-developed phoswich-type neutron detector at 10.8 km altitude over Japan. The measured neutron energy spectrum using the phoswich neutron detector was compared with other on-board measurements using a multi-sphere moderator neutron detector, so called Bonner ball and the measurement on the ground using an organic liquid scintillator, and with the calculations using the LUIN2000, EXPACS and RMC codes.
Takada, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*; Nakamura, Takashi*; Baba, Mamoru*; Homma, Toshihiro*; Endo, Akira; Tanimura, Yoshihiko
Journal of Nuclear Science and Technology, 47(10), p.917 - 931, 2010/10
Times Cited Count：6 Percentile：40.28(Nuclear Science & Technology)A phoswich-type neutron detector was developed in order to measure high-energy cosmic-ray neutron spectrum in aircrafts. The neutron detector consists of a 121.7 mm diameter and a 121.7 mm long EJ309 organic liquid scintillator covered with a 15 mm thick EJ299-13 outer plastic scintillator. Neutron response functions of the detector are required for an unfolding method to get the energy spectrum. The neutron response functions were evaluated from measurements using quasi-monoenergetic neutron sources of various peak energies from 35 to 78 MeV and from the MCNPX simulation. Light output and scintillation attenuation in the scintillator were measured for proton, deuteron and helium-ion beams. The measured neutron response functions well agreed with the MCNPX simulation. Neutron response matrix was created up to 300 MeV neutron energy based on the MCNPX simulation in order to cover the wide neutron energy range in the fight experiment. Photon response matrix also was created up to 50 MeV.
Yajima, Kazuaki*; Yasuda, Hiroshi*; Takada, Masashi*; Sato, Tatsuhiko; Goka, Tateo*; Matsumoto, Haruhisa*; Nakamura, Takashi*
Journal of Nuclear Science and Technology, 47(1), p.31 - 39, 2010/01
Times Cited Count：11 Percentile：59.22(Nuclear Science & Technology)Cosmic-ray neutron energy spectra from thermal to 15 MeV were measured with the multi-moderator spectrometer named the Bonner Ball Neutron Detector (BBND) at aviation altitude (9-11 km). Four flights were carried out around the Nagoya Airport in Japan. The measured data were unfolded using the maximum entropy deconvolution code MAXED, and the derived spectra agreed with calculated results using PHITS-based Analytical Radiation Model in the Atmosphere (PARMA) based on the Monte Carlo calculations by Particle and Heavy Ion Transport code System (PHITS). The results of the aircraft measurement verified the accuracy of model calculation.
Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira; Shigyo, Nobuhiro*; Yasuda, Hiroshi*; Takada, Masashi*; Yajima, Kazuaki*; Nakamura, Takashi
Nuclear Technology, 168(1), p.113 - 117, 2009/10
Times Cited Count：1 Percentile：10.22(Nuclear Science & Technology)The details of the features of DARWIN will be presented at the meeting, together with the recent improvements of the system such as the implementation of the function for estimating neutron spectra using the unfolding technique.
Torii, Tatsuo; Sugita, Takeshi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*
Geophysical Research Letters, 36(13), p.L13804_1 - L13804_4, 2009/07
Times Cited Count：57 Percentile：80.7(Geosciences, Multidisciplinary)Fluctuations of energetic radiation that seemed to be caused by a summer thunderstorm were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy 
rays having a continuous energy spectrum up to 10 MeV or more. As for the feature of these fluctuations, it seems naturally that such fluctuations are caused by the bremsstrahlung photons generated by the energetic electrons produced continuously with an intense electric field in the thundercloud rather than originated in the process of lightning discharge.
Yasuda, Hiroshi*; Yajima, Kazuaki*; Sato, Tatsuhiko; Takada, Masashi*; Nakamura, Takashi*
Health Physics, 96(6), p.655 - 660, 2009/06
Times Cited Count：11 Percentile：59.85(Environmental Sciences)Cosmic radiation exposure of aircraft crew is generally evaluated by numerical simulations and those are desirably verified by measurements. We examined the applicability of selected transportable neutron monitors that are commercially available for measurements of neutron ambient dose equivalent.
Torii, Tatsuo; Sugita, Takeshi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*
Taiki Denki Gakkai-Shi, 3(1), p.111 - 112, 2009/00
Fluctuations of energetic radiation that were seemed to be caused by a summer thunderstorm activity were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy rays having a continuous energy spectrum up to 10 MeV or more. As for the feature of these fluctuations, it seems naturally that such fluctuations are caused by the bremsstrahlung photons generated by the runaway electrons produced continuously with an intense electric field in the thundercloud rather than originated in the process of lightning discharge.
Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira; Shigyo, Nobuhiro*; Yasuda, Hiroshi*; Takada, Masashi*; Yajima, Kazuaki*; Nakamura, Takashi
Transactions of the American Nuclear Society, 99(1), P. 589, 2008/11
A dose monitoring system applicable to various radiations with wide energy ranges, DARWIN, has been developed for measuring dose rates in workspaces and surrounding environments of accelerator facilities. DARWIN satisfies the following features: (1) capable of monitoring doses from neutrons, photons and muons over wide energy ranges, from thermal energy to 1 GeV, 150 keV to 100 MeV, and 1 MeV to 100 GeV, respectively, (2) high sensitivity and precision, more than 10 times as sensitive as conventional moderator-based survey instruments for neutrons, (3) easy to operate with a simple user-interface, and (4) light weighted for movability. The commercial version of DARWIN is expected to be available in near future.
Sato, Tatsuhiko; Yasuda, Hiroshi*; Takada, Masashi*; Yajima, Kazuaki*; Nakamura, Takashi
no journal, ,
We developed the PHITS-based Analytical Radiation Model in the Atmosphere.
Torii, Tatsuo; Sugita, Takeshi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*
no journal, ,
Fluctuations of energetic radiation that were seemed to be caused by a summer thunderstorm activity were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy rays having a continuous energy spectrum up to 10 MeV or more. As for the feature of these fluctuations, it seems naturally that such fluctuations are caused by the bremsstrahlung photons generated by the runaway electrons produced continuously with an intense electric field in the thundercloud rather than originated in the process of lightning discharge. The 5-inch NaI detector used in the observation was so sensitive to photons that it could not have differentiated electrons from photons even if high-energy electrons had been incident upon the detector. When conducting the analysis of energy spectrum, sufficient convergence was achieved in the calculation even in the case where only the sensitivity to photons was considered.
Torii, Tatsuo; Yasuda, Hiroshi*; Yajima, Kazuaki*; Sugita, Takeshi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*
no journal, ,
Fluctuations of energetic radiation that were seemed to be caused by a summer thunderstorm were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy rays having a continuous energy spectrum up to 10 MeV or more. As for the feature of these fluctuations, it seems naturally that such fluctuations are caused by the bremsstrahlung photons generated by the energetic electrons produced continuously with an intense electric field in the thundercloud rather than originated in the process of lightning discharge.
Torii, Tatsuo; Sugita, Takeshi*; Tsuchiya, Harufumi*; Tanabe, Sachiko*; Kimura, Yoshihisa*; Kamogawa, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*
no journal, ,
The dose rate of the -rays increases in association with the activities of the thunderstorm. They were observed on the ground in the winter season of Japan. As an observed result, the following two types of the radiation enhancements have been found during the winter thunderstorm activities; the gradual variation of photon intensity with energy of a few MeV, and the burst type of the radiation that is attributed to the injection of high energy photons with the energy over 10 MeV. Furthermore, fluctuations of energetic radiation that were seemed to be caused by a summer thunderstorm activity were observed at the top of Mt. Fuji. The largest of such fluctuations was gradual and lasted for about 20 minutes, and was found to be high-energy rays having a continuous energy spectrum up to 10 MeV or more.
Yasuda, Hiroshi*; Yajima, Kazuaki*; Takada, Masashi*; Nakamura, Takashi*; Fukuda, Mitsuhiro*; Sato, Tatsuhiko; Naganuma, Takeshi*; Onishi, Takeo*
no journal, ,
A novel survey meter for application to future interplanetary exploration has been developed. It is expected that the survey meter will measure separately exact doses of various cosmic-ray particles at any places even on the ground of moon and Mars. This feature surpasses those of other onboard active monitors or present crew personal dosimeters.
raysYamazaki, Takumi; Takada, Chie; Nakamura, Keisuke; Sagawa, Naoki; Hoshi, Katsuya; Nakagawa, Takahiro; Takimoto, Misaki; Tanimura, Yoshihiko*; Takahashi, Fumiaki; Momose, Takumaro; et al.
no journal, ,
no abstracts in English
Takahashi, Fumiaki; Ishimori, Yuu; Inagaki, Masayo*; Omori, Yasutaka*; Sanada, Tetsuya*; Sugino, Masato*; Furukawa, Masahide*; Hosoda, Masahiro*; Manabe, Kentaro; Yajima, Kazuaki*; et al.
no journal, ,
The Japan Health Physics Society (JHPS) established a committee on dose assessments of Japanese population in August, 2015. The committee consists of 12 members (researchers and technicians) who are engaged in natural radiation measurements, radiation monitoring, radiation dose assessment and so on. Discussion have been made on dose assessments for daily life exposure in Japan. At the first meeting, stragedy of the committee was discussed and terrestrial radiation, cosmic radiation. Radon and radioactivity in food were defined as the radiological source to be investigated. It was also decided that the committee also would investigate influential factors (e.g., dose assessment model, daily life pattern) on radiation dose assessments. In addition, the committee has a plan to make discussions how JHPS should undertake this issue in future. At the 49th Annual meeting of JHPS, the committee members report their activities and make discussions on radiation dose assessment of Japanese population with the participants to the meeting.
Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Yajima, Kazuaki*; Aono, Tatsuo*
no journal, ,
no abstracts in English
