Faculty Profiles - URITANI Akira

Papers - URITANI Akira

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Scintillation properties of composite ceramic YAG and its capability on pulse shape descrimination Reviewed

Takayuki Yanagida, Kenichi Watanabe, Yutaka Fujimoto, Akira Uritani, Hideki Yagi and Takagimi Yanagitani

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN ( 122 ) page： 1016-1019 2014.12

Language：English Publishing type：Research paper (scientific journal)

Transparent ceramic composite of non-doped and Ce-doped YAG was prepared by Konoshima Chemical with the vacuum sintering technique and investigated on pulse shape discrimination capability for functional collimator. Scintillation responses such as X-ray induced radioluminescence and decay time profiles of non-doped and Ce-doped YAG were evaluated. Pulse shape discrimination capability of the composite ceramic was evaluated by Cs-137 662 keV gamma-ray irradiation. As a result, clear separation of gamma-ray events at non-doped or Ce-doped YAG layers was observed in two dimensional histogram by using signal processing with two different shaping times. (C) 2014 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.122.1016

Study on in situ calibration for neutron flux monitor in the Large Helical Device based on Monte Carlo calculations Reviewed

Y. Nakano, A. Yamazaki, K. Watanabe, A. Uritani, K. Ogawa, M. Isobe

Rev. Sci. Instrum. Vol. 85 ( 11 ) page： 11E116-11E116-3 2014.11

Language：English Publishing type：Research paper (scientific journal)

Neutron monitoring is important to manage safety of fusion experiment facilities because neutrons are generated in fusion reactions. Monte Carlo simulations play an important role in evaluating the influence of neutron scattering from various structures and correcting differences between deuterium plasma experiments and in situ calibration experiments. We evaluated these influences based on differences between the both experiments at Large Helical Device using Monte Carlo simulation code MCNP5. A difference between the both experiments in absolute detection efficiency of the fission chamber between O-ports is estimated to be the biggest of all monitors. We additionally evaluated correction coefficients for some neutron monitors.

DOI： 10.1063/1.4891049

Progress in development of the neutron profile monitor for the large helical devicea Reviewed

K. Ogawa, M. Isobe, E. Takada, Y. Uchida, K. Ochiai, H. Tomita, A. Uritani, T. Kobuchi and Y. Takeiri

Rev. Sci. Instrum. Vol. 85 ( 11 ) page： 11E110-11E110-3 2014.11

Language：English Publishing type：Research paper (scientific journal)

The neutron profile monitor stably operated at a high-count-rate for deuterium operations in the Large Helical Device has been developed to enhance the research on the fast-ion confinement. It is composed of a multichannel collimator, scintillation-detectors, and a field programmable gate array circuit. The entire neutron detector system was tested using an accelerator-based neutron generator. This system stably acquires the pulse data without any data loss at high-count-rate conditions up to 8 × 105 counts per second.

DOI： 10.1063/1.4890399

Wide dynamic range neutron flux monitor having fast time response for the Large Helical Device) Reviewed

M. Isobe, K. Ogawa, H. Miyake, H. Hayashi, T. Kobuchi, Y. Nakano, K. Watanabe, A. Uritani, T. Misawa, T. Nishitani, M. Tomitaka, T. Kumagai, Y. Mashiyama, D. Ito, S. Kono, M. Yamauchi and Y. Takeiri

Rev. Sci. Instrum. Vol. 85 ( 11 ) page： 11E114-11E114-4 2014.11

Language：English Publishing type：Research paper (scientific journal)

A fast time response, wide dynamic range neutron flux monitor has been developed toward the LHD deuterium operation by using leading-edge signal processing technologies providing maximum counting rate up to ~5 x 10^9 counts/s. Because a maximum total neutron emission rate over 1 x 10^16 n/s is predicted in neutral beam-heated LHD plasmas, fast response and wide dynamic range capabilities of the system are essential. Preliminary tests have demonstrated successful performance as a wide dynamic range monitor along the design.

DOI： 10.1063/1.4891049

Study on In-Situ Calibration for Neutron Monitor in the Helical Type Fusion Experimental Device Based on Monte Carlo Calculations Reviewed

Y. Nakano, A. Yamazaki, K. Watanabe, A. Uritani, K. Ogawa, M. Isobe

Plasma and Fusion Research Vol. 9 page： 3405141-1 - 3405141-4 2014.10

Language：English Publishing type：Research paper (scientific journal)

Monte Carlo simulations in design of neutron monitors for fusion experimental devices play an important role
to evaluate the influence of scattering from various structures and to correct differences between neutron energies from calibration source and fusion plasma. We have developed an automated input file generation code based on finely segmented helical coil approximation. In this paper, we study the optimal number of divisions of segmented geometry from viewpoints of simulation precision and required calculation time. We conclude that results with more than 360 divisions saturate into the result with fully fine simulation. And we evaluate influence of neutron scattering from a miniature train, a railroad and supporting structures used in in-situ calibration experiments at LHD.

Study on Neutron detector using transparent rubber sheet with dispersed small pieces of LiCaAlF₆ Scintillator Invited

Vol. 40 ( 1 ) page： 67-70 2014.3

巻頭言　福島復興に向けた放射線計測研究者への期待

瓜谷章

放射線 Vol. 39 ( 4 ) page： 151 2014.2

Neutron TOF Experiments Using Transparent Rubber Sheet Type Neutron Detector with Dispersed Small Pieces of LiCaAlF₆ Scintillator Reviewed

Dai Sugimoto, Kenichi Watanabe, Katsuya Hirota, Atushi Yamazaki, Akira Uritani, Tetsuo Iguchi, Kentaro Fukuda, Sumito Ishidu, Noriaki Kawaguchi, Takayuki Yanagida, Yutaka Fujimoto, Akira Yoshikawa, Hiroyuki Hasemi, Kouichi Kino, Yoshiaki Kiyanagi

Physics Procedia Vol. 60 page： 349-355 2014

Scintillation Properties of LiF-SrF₂ and LiF-CaF₂ Eutectic Reviewed

Noriaki Kawaguchi, Takayuki Yanagida, Yutaka Fujimoto, Yuki Furuya, Yoshisuke Futami, Akihiro Yamaji, Kenichi Watanabe, Atsushi Yamazaki, Akira Uritani, Shinji Kajimoto, Hiroshi Fukumura, Shunsuke Kurosawa, Yuui Yokota, Jan Pejchal, Akira Yoshikawa

Journal of Luminescence Vol. 144 page： 212-216 2013.12

3. Radiation Measurement in Fusion Facility 3.3 Fundamentals and Applications of Neutron Measurement Invited

Akira URITANI

J. Plasma Fusion Research Vol. 89 ( 10 ) page： 686-690 2013.10

Neutron Detection with LiCaAlF₆ Scintillator Doped with 3d-transition Metal Reviewed

Radiation Measurements Vol. 55 page： 128-131 2013.8

Language：English Publishing type：Research paper (scientific journal)

We have developed a novel micro-size dosimeter using an optical fiber probe coupled with a photostimulable storage phosphor, such as BaFBr:Eu2+. Our micro-size dosimeter is based on the concept in which the radiation dose response is temporally compressed by using integrating-type dosimeter elements, such as a photostimulable storage phosphor, and the signal-to-noise ratio is improved to downsize the dosimeter probe. We fabricate the prototype dosimeter probe which has the detectable volume of 100 mm thick and 400 mm diameter and the outer diameter of 900 mm. The lower limit of detectable dose, which is defined as three times the noise level, is evaluated to be 0.9 mGy. This value is much smaller than the typical irradiation dose (a few Gy per treatment) in the radiotherapy. We, therefore, conclude that the proposed micro-size dosimeter can be a promising candidate of in-vivo and on-line dose monitor in the
radiotherapy.

Development of a Micro-Size Dosimeter Using an Optical Fiber Probe Based on Photostimulable Phosphorescence Reviewed

Kenichi Watanabe, Atsushi Yamazaki, Kotaro Nakahashi, Hidefumi Miyamae, Akira Uritani, Eiji Ariga

Radiation Measurements Vol. 55 page： 64-67 2013.8

Language：English Publishing type：Research paper (scientific journal)

Origin of Fast Scintillation Components of LiCaAlF₆ Crystals Reviewed

Masanori Koshimizu, Takayuki Yanagida, Yutaka Fujimoto, Atsushi Yamazaki, Kenichi Watanabe, Akira Uritani, Kentaro Fukuda, Noriaki Kawaguchi, Shunji Kishimoto, and Keisuke Asai

Applied Physics Express Vol. 6 page： 062061-1 - 062061-3 2013.5

Language：English Publishing type：Research paper (scientific journal)

The origin of the fast scintillation component of Ce-doped LiCaAlF6 crystal excited by gamma ray irradiation was studied with X-ray and vacuum
ultraviolet (VUV) irradiation. A fast luminescence component was observed under VUV irradiation and was ascribed to luminescence at defects in
the host matrix on the basis of VUV spectroscopy. No fast scintillation component was observed in the scintillation time profile under X-ray
irradiation. The fast scintillation component under gamma ray irradiation can be concluded to be the result of Cherenkov radiation from energetic
secondary electrons.

Ce-doped LiF-SrF₂ Eutectic Scintillators for Thermal Neutron Detection Produced at Different Solidification Rates Reviewed

Takayuki Yanagida, Yutaka Fujimoto, Kentaro Fukuda, Noriaki Kawaguchi, Kenichi Watanabe, Atsushi Yamazaki, Akira Uritani, Valery Chani

Optical Materials Vol. 35 ( 7 ) page： 1449-1454 2013.5

Study on Background Gamma-Ray Reduction Using a Compton Backscattering Coincidence Technique

Takashi Takagi, Kenichi Watanabe, Atsushi Yamazaki, and Akira Uritani

IEEE TRANSACTIONS ON NUCLEAR SCIENCE Vol. 60 ( 2 ) page： 550-554 2013.4

Temperature Dependence of Neutron-Gamma Discrimination Based on Pulse Shape Discrimination Technique in a Ce:LiCaAlF₆ Scintillator

Kenichi Watanabe, Yoshiyuki Kondo, Atsushi Yamazaki, Akira Uritani, Tetsuo Iguchi, Noriaki Kawaguchi, Kentaro Fukuda, Sumito Ishidu, Takayuki Yanagida, Yutaka Fujimoto, and Akira Yoshikawa

IEEE TRANSACTIONS ON NUCLEAR SCIENCE Vol. 60 ( 2 ) page： 959-962 2013.4

Two-dimensional Differential Calibration Method for a Neutron Dosimeter Using a Thermal Neutron Beam Reviewed

Matsumoto, Tetsuro; Harano, Hideki; Masuda, Akihiko; Nishiyama, Jun; Matsue, Hideaki; Uritani, Akira; Nunomiya, Tomoya

Vol. 155 ( 4 ) page： 505-511 2013.3

Eu-doped ⁶LiF-SrF₂ Eutectic Scintillators for Neutron Detection Reviewed

Takayuki Yanagida, Kentaro Fukuda, Yutaka Fujimoto, Noriaki Kawaguchi, Shunsuke Kurosawa, Atsushi Yamazaki, Kenichi Watanabe, Yoshisuke Futami, Yuui Yokota, Jan Pejchal, Akira Yoshikawa, Akira Uritani, Tetsuo Iguchi

Vol. 34 ( 5 ) page： 868-871 2012.3

Ultrafast Transparent Ceramic Scintillators Using the Yb³⁺ Charge Transfer Luminescence in RE₂O₃ Host Reviewed

Takayuki Yanagida, Yutaka Fujimoto, Shunsuke Kurosawa, Kenichi Watanabe, Hideki Yagi, Takagimi Yanagitani, Vitezslav Jary, Yoshisuke Futami, Yuui Yokota, Akira Yoshikawa, Akira Uritani, Tetsuo Iguchi, and Martin Nikl

Applied Physics Express 4 (2011) 126402 Vol. 4 page： 126402-126404 2011.12

Language：English Publishing type：Research paper (scientific journal)

We report a new discovery of Yb3+-doped ultrafast scintillators based on the Yb3+ charge transfer luminescence. Transparent ceramic Yb3+-doped Y2O3, Sc2O3, Lu2O3, and Yb2O3 were prepared by sintering. When irradiated by γ- and X-rays, they showed a well detectable photoabsorption peak in the pulse height spectra and ultrafast scintillation decay dominated by the decay time of about 1 ns. For the first time, the Yb3+-doped oxide materials show detectable scintillation in the pulse height measurement at room temperature with ultrafast scintillation decay.

Feasibility Study on a Micro-Size Dosimeter Using an Optical Fiber Probe Based on a Photostimulable Phosphorescence Reviewed

Kotaro Nakahashi, Kenichi Watanabe, Akira Uritani, Atsushi Yamazaki, Eiji Ariga

Radiation Measurement Vol. 46 ( 12 ) page： 1547-1550 2011.12

Language：English Publishing type：Research paper (scientific journal)

We propose a novel micro-size dosimeter using an optical fiber probe based on the PSL from the BaFBr:Eu2þ. Through basic experiments using the prototype dosimeter, the feasibility of the proposed dose monitoring method has been confirmed.We confirmthat increasing the stimulus laser poweris effective to improve the signal to noise ratio. The lower limit of detectable dose of the prototype dosimeter probe having sensitive region with the diameter of 200 mm is preliminarily estimated to be 11 mGy for a Co-60 gamma-rays. This value is much smaller than the typical irradiation dose (a few Gy per treatment) in the radiotherapy.We can measure the dose in a few hundred subdivisions during a treatment. We, therefore, conclude that the
proposed micro-size dosimeter can be a promising candidate of in-vivo and on-line dose monitor in the
radiotherapy.

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