Faculty Profiles - URITANI Akira

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Performance of Neutron Energy Spectrometer with Onion-like Single Bonner Sphere Using TRUST Eu:LiCAF Scintillator

T. Mizukoshi, K. Watanabe, A. Uritani, A. Yamazaki, T. Iguchi, T. Ogata, T. Muramatsu, T. Matsumoto, A. Masuda

12th International Workshop on Ionizing Radiation Moitoring

Event date： 2016.12

Language：English Presentation type：Poster presentation

Country：Japan

In order to measure neutron energy spectra, the conventional Bonner Sphere Spectrometers (BSS) are widely used. Operators should place these spheres in several times to a measurement point where a radiation dose might be relatively high. In order to reduce this effort, a novel neutron energy spectrometer using an onion-like single Bonner sphere has been proposed by our group. This Bonner sphere has multiple sensitive spherical shell layers in a single sphere. In this spectrometer, a band-shaped thermal neutron detection medium, which consists of a Transparent RUbber SheeT type Eu:LiCaAlF6 (TRUST Eu:LiCAF) scintillator and a wavelength-shifting (WLS) fiber readout, was looped to each sphere at equal angular intervals. The amount of Eu:LiCAF neutron converter is reduced near polar region in order to uniform the directional sensitivity (Fig. 1). The TRUST Eu:LiCAF scintillator is flexible and shows a peak shape corresponding to thermal neutron absorption events in the pulse height spectrum. We fabricated the prototype detector with five sensitive layers using the TRUST LiCAF scintillators. The directionally variation of the detector sensitivity is less than 7% except the direction, in which there are PMTs, their supporting structures and a hole in the moderator sphere for drawing out the WLS fibers. The fabricated detector shows excellent directional uniformity of the neutron sensitivity.

パルス中性子透過分光法を用いた日本刀の製造過程における組織変化の解析 International conference

堀元紀、田中眞奈子、山﨑淳、渡辺賢一、鬼柳善明、瓜谷章

日本中性子科学会第16回年会

Event date： 2016.12

Language：Japanese Presentation type：Oral presentation (general)

Venue：名古屋大学 Country：Japan

本研究グループは、これまでパルス中性子透過分光法を用いて非破壊で日本刀や火縄銃などの鉄文化財内部の結晶組織構造情報を解析し、具体的な製造方法や材料特性を解明することを目的に研究を行ってきた。前報では、パルス中性子透過分光法を用いて日本刀の製造過程の試料の測定を行い、鍛造や熱処理加工による結晶組織の変化を非破壊で確認した。本報では、同試料の棟から刃にかけて、2ピクセルごとに細かく解析を行い、場所による加工の影響を確認した。最終的には各製造過程における組織情報の2Dマッピング像を得ることを目的としている。
　結晶格子面間隔ｄに着目して解析したところ、焼入れを施す前の試料では刃から棟にかけての間隔は一定だが、施した後の試料では刀の棟では面間隔が小さくなり、刃では大きくなった。棟は焼入れの際に焼刃土が盛られる為、除冷されることで炭素量の小さいパーライトとフェライトに相変態し、刃は急冷され炭素量の多いマルテンサイトに変態したと思われる。棟と刃で異なる組織に変化した事で、面間隔に差が生じたと考えられる。その後の過程において焼き戻しを行った試料では、刃側の面間隔が少し小さくなった。再加熱によって炭素が抜け、組織が変化し、体積が縮小した為と考えられる。今後、まだ解析を行ってない製造過程試料の解析を進めていく予定である。

加速器駆動中性子源の現状と将来 Invited

土田一輝，鬼柳善明，瓜谷章

日本放射線安全管理学会　第15回学術大会

Basic study of a Compton scattering camera using a pixelated TlBr detector International conference

Motohiro Matsumura, Kenichi Watanabe, Atsushi Yamazaki, Sachiko Yoshihashi Akira Uritani, Hiroki Sunaba, Nobumichi Nagano and Keitaro Hitomi

Event date： 2016.10 - 2016.11

Language：English Presentation type：Poster presentation

Venue：Strasbourg, France Country：France

Compton scattering cameras have exciting potentials for wide applications such as the medical imaging, radioactive decontamination and so on. Thallium bromide (TlBr) is one of the promising candidates for detectors in the Compton scattering camera because of operating stably at room temperature and the good energy resolutions for gamma rays.
The requirements for constructing Compton scattering cameras include the good energy resolutions and the good position resolutions for incident gamma-rays. In case of pixelated detectors, the energy and position resolutions for near-anode events become worse because the pulse height decreases due to the weighting potential distortion. Charge-sharing events in adjacent pixels contribute also to deteriorate the energy and position resolutions. Therefore, development of pulse waveform analysis methods is necessary for using the pixelated TlBr detectors for the Compton scattering cameras.
In this paper, we discuss the basic issues for using the pixelated TlBr detectors as the Compton scattering cameras. We have already demonstrated the depth-sensing capability in the pixelated detector by using anode/cathode signal ratio. However, the detector sharing a cathode for all pixels cannot reconstruct the depth-of-interaction from the anode/cathode ratio. We, therefore, adopt a new depth-sensing method, which derives the depth-of-interaction from electron drift time extracted with waveform processing. We confirmed that the depth-of-interaction estimated with the proposed procedure is well consistent with expectation from Compton scattering kinematics.

Ce concentration dependence of quenching effects in Ce:CaF₂ small size dosimeters International conference

Yuho Hirata, Kenichi Watanabe, Akira Uritani, Atsushi Yamazaki, Yusuke KOBA, Naruhiro MATSUFUJI, Takayuki YANAGIDA, Kentaro FUKUDA

Event date： 2016.10 - 2016.11

Language：English Presentation type：Poster presentation

Venue：Strasbourg, France Country：France

Heavy ion therapies can form fine and complex dose distributions and reduce undesired irradiation into normal organs. Misalignment of an irradiation position may cause significant accident. In order to accurately estimate the irradiation dose, dosimeters are required to be inserted into an affected region in a patient body. We, therefore, are developing a small size dosimeter consisting of an optical fiber and an optically stimulated luminescence (OSL) element. We evaluated the characteristics of OSL used small size dosimeters with a high energy carbon beam. OSL materials show quenching effects when irradiated by high linear energy transfer (LET) particles. We assumed the quenching effect was caused by local occupation of trap centers due to high density ionization. The quenching effect, therefore, depends on the density of trap centers. Ce:CaF₂ is one of the most useful OSL elements. The OSL signal intensity is increased with Ce concentration. This means high Ce concentration make high density of trap centers. In this paper, we evaluate the quenching effect with different Ce concentration doped CaF₂. We prepared different Ce concentration as 0.1, 0.5 and 5.0 % doped CaF₂. Carbon ions were irradiated to the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The fabricated dosimeters were set behind the water equivalent acrylic phantom. The LET value of carbon ions were varied by changing the phantom thickness. The dosimeters showed different level quenching. Luminescence efficiencies increased with Ce concentration. We confirmed that the quenching effect depends on the density of trap centers.

The design for BNCT facility based on radiation dose estimation International conference

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

International Congress on Neutron Capture Therapy 17

Design of a Beam Shaping Assembly for the Nagoya University BNCT Engineering Study System International conference

Y. Menjo, Y. Kiyanagi, K. Tsuchida, A. Yamazaki, K. Watanabe and A. Uritani

International Congress on Neutron Capture Therapy 17

Event date： 2016.10

Language：English Presentation type：Poster presentation

Country：Japan

The proton energy is low and Li produces higher neutron intensity than Be at this energy. We decided to use a sealed Li target. The beam shaping assembly (BSA) will be different from the one designed for higher energy protons. In order to manufacturing a high efficiency BSA, we performed simulation calculations to design a sealed Li target BNCT system that fullfiled the conditions indicated in IAEA-TECDOC-1223.

CompactAccelerator-DrivenBNCT SystemUsed Sealed LithiumTarget International conference

K. Tsuchida, Y. Kiyanagi, A. Uritani, K. Watanabe, S. Yoshihashi, Y. Menjo, D. Furuzawa, Y. Tsuji, T. Tsuneyoshi, H. Shimizu, K. Hirota, G. Ichikawa, A. Sagara and Y. Hamaji

17th International Congress on Neutron Capture Therapy

Event date： 2016.10

Language：English Presentation type：Poster presentation

Country：Japan

A compact sealed lithium target is underdevelopingfor BNCT application in combination with a Dynamitron(2.8MeV,15mA). Low energy protons incident on lithium target are one of the most suitable reaction for accelerator-based BNCT [1, 2], because a sufficient flux and good quality of epi thermal neutron beam can be obtained by using a compact beam shaping assembly (BSA) and also radiationexposer of medical staffs can be reduced by lowering the activationof accelerator facility. However, metallic lithium has several difficulties in chemical properties (low melting point, high chemical activityand 7Be production) as a target material. For resolving those isssues, we are developing a compactand sealedLi target. A thin lithium layer (0.14mm) is set on the embossed structure of a tantalum plate and coveredby a thin titanium alloy foil to confine liquid lithium and radio isotopes (Be-7, T) in the target. The low-energy and high current proton beam is passing through a titanium foil and irradiated to the lithium layer. Strong turbulent flow is arose with ribs in cooling water channels of the target and had been confirmed to be able to remove high beam flux of more than 10MW/m2. It can reduce the irradiation area of the proton beam (42kW) down to the60mm squareon theLi target Neutrons withtheenergies ofless than1MeV are produced duetothe 7Li(p,n)7Bereaction by the irradiation of the 2.8MeV proton beams and could be moderated using a compact beam shaping assembly (1m in dia.) to meet all the conditions indicated in the IAEATECDOC-1223.
We are constructing a compact accelerator-driven neutron source to confirm the practical reliability of thesealed lithiumtargetfortheBNCTapplication in theNagoya University.

名古屋大学NUANSの中性子発生ターゲットの研究開発

瓜谷章

日本原子力学会2016年秋の大会

光刺激蛍光体を用いた光ファイバ型小型線量計のヘリウム線に対する基礎的な応答の評価

平田悠歩、瓜谷章、渡辺賢一、吉橋幸子、山﨑淳、古場裕介、松藤成弘、歳藤利行、柳田健之、福田健太郎

日本原子力学会2016年秋の大会

TRUST Eu:LiCAFを用いた多重球殻構造を有する一球型中性子スペクトロメータの評価

水越友亮、渡辺賢一、瓜谷章、山崎淳、井口哲夫、尾方智洋、村松貴史、松本哲郎、増田明彦

日本原子力学会2016年秋の大会

Nondestructive study on metallurgical characteristics of traditional Japanese sword throughout the manufacturing process by pulsed neutron imaging International conference

A Design Study of a Neutron Source for Pulsed Neutron Imaging at Kyoto University Research Reactor Institute Linac International conference

Y. Kiyanagi, A. Haradda, A. Uritani

Development of the Electrostatic Accelerator driven BNCT neutron source at Nagoya University

Event date： 2016.8

Language：Japanese Presentation type：Oral presentation (general)

Country：Japan

A neutron source based on an electrostatic accelerator, Dynamitron (2.8MeV, 15mA), is under construction at Nagoya University. The neutron source is planned to be used for boron neutron capture therapy and for science and engineering applications. Due to the low proton energy a Li target is used to obtain much higher neutron intensity than a Be target. The accelerator was installed in 20015. The first beam was delivered at 2.8MeV and 11mA in January 2016. Commissioning is underway for stable operation. A design study on a beam shaping assembly (BSA) has been performed under the condition of the IAEA-TECDOC-1223. A BSA that can produce epi-thermal neutron intensity over 10⁹ n/cm²/sec was designed fulfilling the condition. Heat removal is one of serious issues of the Li target. Therefore, we performed preliminary experiment using an electron beam heating method. The result indicated that the cooling system developed will be able to remove the heat expected at full power accelerator operation.

名古屋大学における加速器BNCT 用システムの開発―（１）事業概要と加速器について ―

土田一輝、鬼柳善明、瓜谷章、渡辺賢一、吉橋幸子、山崎淳、清水裕彦、北口雅暁、広田克也、市川豪、NUANS グループ

第13回日本中性子捕捉療法学会学術大会

名古屋大学における加速器BNCT 用システムの開発―（３） Li 封入型ターゲットの除熱方法の検討 ―

古澤大貴、瓜谷章、山崎淳、鬼柳善明、土田一輝、辻義之、恒吉達矢、浜地志憲、時谷政行、田村仁、相良明男

第13回日本中性子捕捉療法学会学術大会

名古屋大学における加速器BNCT 用システムの開発―（２）Beam Shaping Assembly の設計検討 ―

瓜谷章、校條洋輔、土田一輝、鬼柳善明、清水裕彦、広田克也、市川豪、渡辺賢一、山﨑淳、吉橋幸子、NUANSグループ

第13回日本中性子捕捉療法学会学術大会

Development of Accelerator-based BNCT System in Nagoya University 3

Akira Uritani, Yosuke Menjo, Kenichi Watanabe, Atsushi Yamazaki, Katsuya Hirota, Masaaki Kitaguchi, Hirohiko Shimizu,Go Ichikawa, Yoshiaki Kiyanagi and Kazuki Tsuchida

Basic response evaluation of optical fiber type small size dosimeter using optically stimulated luminescence for 225 MeV/u proton ions

Neutron Energy Spectrometer with Onion-like Single Bonner Sphere Using TRSUT Eu:LiCAF Scintillator for High Flux

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