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

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

Rev. Sci. Instrum. 85 巻 ( 11 ) 頁： 11E116-11E116-3 2014年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Rev. Sci. Instrum. 85 巻 ( 11 ) 頁： 11E110-11E110-3 2014年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

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) 査読有り

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. 85 巻 ( 11 ) 頁： 11E114-11E114-4 2014年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Plasma and Fusion Research 9 巻頁： 3405141-1 - 3405141-4 2014年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

小片LiCaAlF₆シンチレータ分散樹脂型中性子検出器の開発招待有り

杉本大、渡辺賢一、山﨑淳、瓜谷章、井口哲夫、福田健太郎、石津澄人、河口範明、柳田建之、藤本裕、吉川彰

放射線 40 巻 ( 1 ) 頁： 67-70 2014年3月

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 39 巻 ( 4 ) 頁： 151 2014年2月

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

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 60 巻頁： 349-355 2014年

Scintillation Properties of LiF-SrF₂ and LiF-CaF₂ Eutectic 査読有り

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 144 巻頁： 212-216 2013年12月

３．核融合施設における放射線計測３．３中性子計測の基礎と実践招待有り

瓜谷章

89 巻 ( 10 ) 頁： 686-690 2013年10月

担当区分：筆頭著者記述言語：日本語

重水素を用いたプラズマ核融合実験においては，中性子の測定は物理的興味の面からも，安全管理の面からも重要である．本講座では，核融合実験における中性子計測で必要とされる基礎知識，すなわち熱中性子と高速中性子の検出原理をその素過程に遡って解説するとともに，基本的な中性子検出器を紹介した．また，核融合実
験装置での中性子測定例として，中性子束モニタ，中性子エネルギー測定，中性子プロファイル測定について解説した．

Neutron Detection with LiCaAlF₆ Scintillator Doped with 3d-transition Metal 査読有り

Radiation Measurements 55 巻頁： 128-131 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Radiation Measurements 55 巻頁： 64-67 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

Origin of Fast Scintillation Components of LiCaAlF₆ Crystals 査読有り

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

Applied Physics Express 6 巻頁： 062061-1 - 062061-3 2013年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Optical Materials 35 巻 ( 7 ) 頁： 1449-1454 2013年5月

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 60 巻 ( 2 ) 頁： 550-554 2013年4月

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 60 巻 ( 2 ) 頁： 959-962 2013年4月

Two-dimensional Differential Calibration Method for a Neutron Dosimeter Using a Thermal Neutron Beam 査読有り

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

155 巻 ( 4 ) 頁： 505-511 2013年3月

Eu-doped ⁶LiF-SrF₂ Eutectic Scintillators for Neutron Detection 査読有り

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

34 巻 ( 5 ) 頁： 868-871 2012年3月

Ultrafast Transparent Ceramic Scintillators Using the Yb³⁺ Charge Transfer Luminescence in RE₂O₃ Host 査読有り

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 4 巻頁： 126402-126404 2011年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 査読有り

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

Radiation Measurement 46 巻 ( 12 ) 頁： 1547-1550 2011年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

Development of Novel Rare Earth Doped Fluoride and Oxide Scintillators for Two-Dimensional Imaging 査読有り

29 巻 ( 12 ) 頁： 1178-1182 2011年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Two topics were focused. The first one was about the gamma-ray scintillator, Pr3+:Lu3Al5O12 (LuAG). The second one was about neutron scintillator, Ce3+:6LiCaAlF6 and Eu2+:6LiCaAlF6 (6LiCAF). Those scintillators have been developed very recently for modern imaging applications in the medical and homeland security fields. In both cases, the rare earth ions are playing the crucial role as emission centers. Pr3+ in LuAG provided fast 5d→4f transition providing noticeably shorter decay time than that of Ce3+. Among several candidate hosts, LuAG showed the best performance. Bulk crystal growth, basic scintillation properties, two-dimensional gamma-ray imaging and positron emission mammography (PEM) application were demonstrated. Due to the international situation, the homeland security was compromized by illicit traffic of explosives, drugs, nuclear materials, etc. and the ways to its improvement became an important R&D topic. For this purpose the Ce and Eu doped LiCAF appeared competitive candidates. Especially, when substitution of 3He neutron detectors was considered, the discrimination ability of gamma-ray from alpha-ray was important. Bulk crystal growth, basic scintillation properties and two-dimensional neutron imaging were demonstrated.

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