研究者詳細 - 瓜谷　章

講演・口頭発表等 - 瓜谷　章

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炭素量の異なる鉄鋼材料のパルス中性子を用いた透過率測定とブラッグエッジ解析国際会議

磯野真理子、塩田佳徳、渡辺賢一、瓜谷章、鬼柳善明、田中眞奈子

日本中性子科学会第14回年会

透明樹脂中分散型シンチレータ（TRUST LiCAF）の中性子検出特性

瓜谷章、杉本大、山﨑拓弥、水越友亮、渡辺賢一、山﨑淳、福田健太郎、石津澄人、河口範明、藤本裕、柳田健之、吉川彰

日本放射線安全管理学会　第13回学術大会

Stereographic Backscattered X-Ray Tomography with Scanning Pencil-Beam for One-Sided Nondestructive Inspection 国際会議

T. Tohyama, A. Yamazaki, K. Watanabe, A. Uritani

IEEE NUCLEAR SCIENCE SYMPOSIUM

開催年月日： 2014年11月

記述言語：英語会議種別：ポスター発表

国名：日本国

Routine maintenance and inspections for large size infrastructure, such as bridges and tunnels, are required due to aging degradation. The nondestructive internal inspection with imaging is quite useful for this purpose. Although the transmission X-ray imaging technique has high spatial resolution, it is unsuitable for large size structures because it is necessary to sandwich objects between an X-ray source and detectors. The backscattered X-ray imaging technique can be used for the internal visualization of large size structures because it can carry out an inspection from one-side of the object. However, it takes long time to obtain a tomographic image based on this technique. Therefore, we proposed a tomography technique based on backscattered X-ray, which is available for large size structures and reduces measurement time, as a one-sided inspection. The proposed system consists of a pencil-beam X-ray source, which can sweep an angle and slide a position, and the X-ray detectors which record the integrated quantity of the backscattered X-rays for every incident angles and source positions. The recorded values are indexes of the line integral of scattering cross section along the incident X-ray beam. Tomographic images can be acquired using image reconstruction procedures based on a stereographic technique. In this paper, we simulated the projection of backscattered X rays using the Monte Carlo simulation code EGS5 to confirm the principle of our tomographic imaging technique. We successfully demonstrated that the stereographic backscattered X-ray tomography was able to reconstruct the tomographic image of the object shape with one-sided inspection. In addition, we experimentally confirmed that a sufficient amount of backscattered X-ray can be acquired.

Characterization of Large Area Transparent RUbber SheeT (TRUST) LiCaAlF₆ Neutron Scintillator 国際会議

K. Watanabe, A. Yamazaki, D. Sugimoto, T. Yamazaki, A. Uritani, T. Iguchi, K. Fukuda, S. Ishidu, T. Yanagida, Y. Fujimoto

IEEE NUCLEAR SCIENCE SYMPOSIUM

開催年月日： 2014年11月

記述言語：英語会議種別：口頭発表（一般）

国名：日本国

Alternatives of standard He-3 neutron detectors have been required to be developed because of the He-3 shortage. We are developing the Eu:LiCaAlF₆ scintillators as one of the candidates for an alternative of the He-3 detector. Although this scintillator has high light yield, it suffers from the interference of gamma rays due to its relatively low a/ß ratio. In addition, synthesis of large Eu:LiCaAlF₆ single crystals requires relatively long time and high cost. In order to solve these problems, we have developed a Transparent RUbber SheeT type Eu:LiCaAlF₆ (TRUST LiCAF) scintillator in which small pieces of Eu:LiCaAlF₆ scintillators are dispersed. The size of small pieces of Eu:LiCaAlF₆ crystals are controlled to be smaller than the ranges of fast electrons induced by gamma rays and larger than the ranges of alphas and tritons produced by ⁶Li(n,t) reaction. Consequently, the signal pulse height of gamma-ray induced events can be reduced smaller than that of neutron induced events. The size or area of this type of scintillator can easily be enlarged using a large size mold in the solidification process of the resin. In this paper we fabricated a relatively large size TRUST LiCAF scintillator and evaluated its basic performances. The TRUST LiCAF scintillator was directly mounted on the window of the photomultiplier tube. Gamma-ray induced events are almost completely eliminated by setting an adequate threshold level. Consequently, sufficiently low gamma-ray detection efficiency was confirmed with keeping adequate neutron detection efficiency.

Gamma-Ray Suppression with Pulse Shape Discrimination Technique for Transparent RUbber SheeT (TRUST) LiCaAlF₆ Neutron Scintillator with Wavelength-Shifting Fiber Readout 国際会議

T. Yamazaki, K. Watanabe, A. Yamazaki, D. Sugimoto, A. Uritani, T. Iguchi, K. Fukuda, S. Ishidu, T. Yanagida

IEEE NUCLEAR SCIENCE SYMPOSIUM

開催年月日： 2014年11月

記述言語：英語会議種別：ポスター発表

国名：日本国

Alternatives to He-3 neutron detectors are required to be developed due to He-3 shortage problem and increase in demand for neutron detectors in security and scientific applications. We have, therefore, developed a Transparent RUbber SheeT type Eu:LiCaAlF₆ (TRUST LiCAF) neutron scintillator. This type of scintillator is made of a transparent rubber sheet in which a large number of small pieces of Eu:LiCaAlF6 scintillator are dispersed. In the TRUST LiCAF scintillator, pulse heights of gamma-ray induced events are suppressed and these events can easily be rejected with pulse height discrimination. In addition, this scintillator can easily be fabricated with large area. For large area scintillators, wavelength-shifting fiber (WLS) fiber readout is quite useful. In this paper, we evaluated the basic performance of the TRUST LiCAF scintillator with WLS fiber readout. WLS fibers were bundled in plate shape. The TRUST LiCAF scintillator with the size of 200x50x5 mm3 was mounted on the WLS fiber plate. Although the peak shape corresponding to the neutron absorption events can clearly be confirmed, gamma-ray induced events also have relatively high pulse heights. These events with relatively high pulse heights is considered to be events produced in the WLS fiber by interactions between gamma rays and the WLS fibers. The scintillation in the WLS fiber has shorter decay time of a few ns compared with the TRUST LiCAF scintillator whose decay time is a few µs. Fiber emission events can be clearly distinguished from TRUST LiCAF scintillator emission events by using the pulse shape discrimination technique. Consequently, gamma-ray detection efficiency can sufficiently be reduced with keeping adequate neutron detection efficiency.

Development of a Novel Neutron Energy Spectrometer Using Onion-like Multi-Shell Single Bonner Sphere 国際会議

K. Watanabe, M. Ushida, A. Yamazaki, A. Uritani, T. Iguchi, T. Ogata, T. Muramatsu

IEEE NUCLEAR SCIENCE SYMPOSIUM

開催年月日： 2014年11月

記述言語：英語会議種別：ポスター発表

国名：日本国

In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. The neutron spectrum can be derived by deconvolution procedures, which reconstruct the spectrum from several Bonner spheres outputs by using their response functions. In this spectrometer, since several measurements with different Bonner spheres are required, operators should bring these spheres many times to the measurement point where the radiation dose might be relatively high. In order to solve this disadvantage, a single Bonner sphere that utilizes difference in spatial distribution of the thermal neutrons in the sphere was proposed. Since the conventional single Bonner sphere spectrometers consist of some small thermal neutron detectors discretely arranged in the sphere or three one-dimensional position sensitive counters perpendicularly arranged, they have considerable directional dependence in the detector response. We have, therefore, proposed a novel neutron energy spectrometer using an onion-line single Bonner sphere, which has multiple sensitive spherical shells as the detector configuration without directional dependence. In this paper, in order to confirm the detector response of the proposed neutron spectrometer, the prototype detector with five sensitive layers was fabricated and basic experiments were carried out. The experimental results are consistent with the expected c simulated with Monte Carlo calculations. The count rates of outer layers increase and the rates of inner layers decrease compared with the direct irradiation condition in which the neutron spectrum is harder. We experimentally confirmed the detector response which reflects the neutron energy spectrum.

Study on Neutron Imaging Technique Using Transparent RUbber SheeT (TRUST) LiCaAlF₆ Neutron Scintillator 国際会議

D. Sugimoto, K. Watanabe, A. Yamazaki, T. Yamazaki, A. Uritani, T. Iguchi, K. Fukuda, S. Ishidzu, T. Yanagida

IEEE NUCLEAR SCIENCE SYMPOSIUM

開催年月日： 2014年11月

記述言語：英語会議種別：ポスター発表

国名：日本国

We have developed Eu:LiCaAlF₆ (Eu:LiCAF) scintillators as a novel He-3 alternative neutron detector. Although this scintillator has various useful properties such as high neutron detection efficiency, high light yield, no hygroscopicity and high transparency, it suffers from the influence of gamma-ray due to its low a/ß ratio. In addition, single crystal scintillators are generally difficult to fabricate detectors with a large area of several tens of square centimeters. To overcome these difficulties, we proposed to disperse small pieces of Eu:LiCAF scintillators into a transparent rubber and form a rubber sheet type scintillator. This type of scintillator is referred to as a Transparent RUbber SheeT (TRUST) LiCAF scintillator. A small piece of Eu:LiCAF scintillator can selectively reject only gamma-ray events due to a difference between ranges of fast electrons induced by gamma rays and 6Li(n,t) reaction products. By dispersing small pieces of Eu:LiCAF crystals into a transparent rubber sheet, the neutron detection efficiency can increase with keeping the gamma-ray event suppression ability. Since a TRUST LiCAF scintillator can easily enlarged its area, a neutron imaging is one of the attractive applications. In this paper, we successfully demonstrate that the TRUST LiCAF scintillator can acquire neutron images. Under the current status, the spatial resolution is evaluated to be less than a few mm.

赤外発光シンチレータを用いた耐放射線性の高い放射線検出器の開発

熊谷洋祐，渡辺賢一，山崎　淳，瓜谷　章

第75回応用物理学会秋季学術講演会

透明樹脂型Eu:LiCaAlF₆シンチレータと波長シフトファイバ読出しを用いた大面積中性子検出器の開発

山﨑拓弥，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，柳田健之

第75回応用物理学会秋季学術講演会

Eu:LiCaAlF₆分散樹脂型シンチレータの発光特性の評価

杉本大，山﨑拓弥，渡辺賢一，山﨑淳，瓜谷章，井口哲夫，福田健太郎，石津澄人，柳田健之

第75回応用物理学会秋季学術講演会

モンテカルロ計算に基づくヘリカル型核融合実験装置の中性子モニタに関する研究（2）モニタ設置位置の検討

仲野裕次，瓜谷章，渡辺賢一，山﨑淳，磯部光孝，小川国大

日本原子力学会 2014年秋の大会

LIBS を用いた固体表面水素分布測定法に関する研究

吉本久晃，瓜谷章，渡辺賢一，山﨑淳，井上龍夫

日本原子力学会 2014年秋の大会

後方散乱X 線断層撮像技術に関する研究

○遠山貴之，瓜谷章，渡辺賢一，山﨑淳，吉田迅

日本原子力学会 2014年秋の大会

名古屋大学における静電加速器を用いたホウ素中性子捕捉療法用システム計画

鬼柳善明、土田一輝、瓜谷章、川端勇矢、山﨑淳、校條洋輔、山崎拓弥、渡辺賢一、市川豪、広田克也、北口雅暁、清水裕彦

第11回日本加速器学会年会

開催年月日： 2014年8月

記述言語：日本語会議種別：口頭発表（一般）

開催地：リンクステーションホール青森（青森市文化会館）国名：日本国

ホウ素中性子補足療法（ＢＮＣＴ）は、ガン部にホウ素薬剤を集め、そこに熱中性子を照射することによって、核反応で発生するLi とα粒子でDNAを切断し癌細胞を殺す方法である。癌細胞を選択的に殺すことができる方法として、他の放射線治療法とは異なった利点を持っている。これまで原子炉中性子を用いた治療が京大炉やJRR-4を用いて行われてきたが、原子炉を病院の中に設置することは難しく、加速器をベースとしたBNCT中性子源の建設が進められている。
我々は、陽子加速器としてIBA社の静電加速器ダイナミトロンを今年度導入し、2018年までにBNCTシステムを開発し、治療への適応の可否を明らかにする計画である。加速エネルギーは2.8 MeVで15 mAの大電流ビームを発生する。発生中性子エネルギーが低い7Li(p, n)反応を採用するため、システムの放射化が少なく、熱外中性子減速材がコンパクトになるというメリットがある。しかし、発熱密度が高いため、融点の低いLiターゲットの除熱などの問題を考えてターゲット設計を進めている。また、減速材システムはMgF2を主たる減速材とし、反射体、コリメータを設置したものを検討している。開発システムの照射条件の目標値は、中性子射出孔において、0.5 eV～10 keVの範囲の熱外中性子束が1×109 n/cm2/s、高速中性子混入率が2×10-13 Gy cm2である。

Development of an accelerator-driven compact neutron source for BNCT in Nagoya University 国際会議

K. Tsuchida, Y. Kiyanagi, A. Uritani, K. Watanabe, H. Shimizu, K. Hirota, M. Kitaguchi

16th International Congress on Neutron Capture Therapy

開催年月日： 2014年6月

記述言語：英語会議種別：口頭発表（一般）

国名：フィンランド共和国

Development of an accelerator-driven compact neutron source has been started in Nagoya University for BNCT application based on a low-energy high-current DC accelerator, which has also extra possibilities of applications to fundamental physics experiments and industry uses.

Fundamental properties of Transparent RUbber SheeT (TRUST) LiCaAlF₆ neutron scintillator 国際会議

Dai Sugimoto, A. Uritani et al.

2014 Symposium on Radiation Measurements and Applications

Response evaluation of a small radiation detector using OSL with optical fiber readout to high energy carbon ions 国際会議

Dai Sugimoto, A. Uritani et al.

2014 Symposium on Radiation Measurements and Applications

Tomographic imaging from one-side using backscattered X-ray 国際会議

K. Watanabe, A. Uritani et al.

2014 Symposium on Radiation Measurements and Applications

Wavelength-shifting fiber signal readout from Transparent Rubber SheeT (TRUST) type LiCaAlF₆ neutron scintillator 国際会議

K. Watanabe, A. Uritani et al.

2014 Symposium on Radiation Measurements and Applications

Wide dynamic range neutron flux monitor having fast time response for the Large Helical Device 国際会議

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

20th Topical Conference on High-Temperature Plasma Diagnostics

開催年月日： 2014年6月

記述言語：英語会議種別：口頭発表（一般）

国名：アメリカ合衆国

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 ~5×10⁹ (cps). Because a maximum total neutron emission rate over 1×10¹⁶ (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 wide dynamic range monitor along the design.

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