Faculty Profiles - URITANI Akira

Papers - URITANI Akira

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Characterization of Kilo Electron Volt Neutron Fluence Standard with the ⁴⁵Sc(p,n)⁴⁵Ti Reaction at NMIJ Reviewed

T. Matsumoto, H. Harano, T. Shimoyama, K. Kudo, and A. Uritani

Radiation Protection and Dosimetry Vol. 126 page： 155-158 2007.8

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

We are developing a national standard of a monoenergetic kilo electron volt neutron field with the 45Sc(p,n)45Ti resonance reaction. A wide resonance yields 27.4 keV neutrons at 0° with respect to the proton beam. The proton energy was precisely determined in the measurement of the relative neutron yield as a function of the proton energy from the threshold energy to 2.942 MeV. Absolute measurement of the monoenergetic neutron fluence was performed using a 3He proportional counter. Relative measurement was also carried out using a Bonner sphere calibrated at our 144 keV standard neutron field. Calibration factors were obtained between the count of a neutron monitor and the neutron fluence. A silicon-surface barrier detector with a 6LiF foil converter was also being developed for the neutron fluence measurement. Successful results were obtained in the tests in the 144 keV standard neutron field.

International Key Comparison of Neutron Fluence Measurements in Mono-energetic Neutron Fields: CCRI(III)-K10 Invited Reviewed

J Chen, Z Wang, C Rong, G Lövestam, A Plompen, N Puglisi, D M Gilliam, C M Eisenhauer, J S Nico, M S Dewey, K Kudo, A Uritani, H Harano, N Takeda, D J Thomas, N J Roberts, A Bennett, P Kolkowski, N N Moisseev, I A Kharitonov, S Guldbakke, H Klein

Metrologia Vol. 44 page： 58 2007

Language：English

CCRI Section III (neutron measurements) conducted a unique key comparison of neutron fluence measurements in mono-energetic neutron fields. In contrast to former comparisons, here the fluence measurements were performed with the participants' instruments in the same neutron fields at the PTB accelerator facility. Seven laboratories - the CIAE (China), IRMM (EC), NMIJ (Japan), NIST (USA), NPL (UK), PTB (Germany) and the VNIIM (Russia) - employed their primary standard reference methods or transfer instruments carefully calibrated against their primary standards, to determine the fluence of 0.144 MeV, 1.2 MeV, 5.0 MeV and 14.8 MeV neutrons and reported calibration coefficients for a selected neutron monitor and each neutron energy with a detailed uncertainty budget for the measurements. The key comparison reference values (KCRV) were finally evaluated as the weighted mean values of the neutron fluence at 1 m distance from the target in vacuum per neutron monitor count. The uncertainties of each KCRV amounted to about 1%. The degree of equivalence (DoE), defined as the deviation of the result reported by the laboratories for each energy from the corresponding KCRV, and the associated expanded uncertainty are also reported. The deviations between the results of two laboratories each with the corresponding expanded uncertainties complete the documentation of the degrees of equivalence.

Convenient Method of Relative Calibration of the Neutron Source Emission Rate between Ddifferent Source Types Reviewed

H.Harano, T.Matsumoto, T.Shimoyama,Y. Sato, A. Uritani, Y.Hino, K. Kudo, T.Michikawa

Nuclear Science, IEEE Transactions on Vol. 53 ( 3 ) page： 1413 - 1417 2006.6

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

Neutron source emission rates are determined by absolute or relative measurement. The relative measurement is performed by comparing between a sample source and a calibrated reference source of the same type. In this calibration, the energy spectra of the sample and reference sources should be identical, since normally there exists energy dependence in the response of neutron detectors. We propose a method of relative calibration of the neutron source emission rate between different source types and spectra. In the present method, a sample source or a calibrated reference source is located at the center of a graphite pile and thermal neutron flux at a special position is monitored and compared. We performed gold foil activation measurements at the NMIJ/AIST graphite pile and revealed that the thermal neutron flux at that position per unit source emission rate is independent of the types of neutron sources. The details of the physical mechanism were examined by calculating the spectral fluence of the neutrons thermalized inside the graphite pile using the MCNP4C code. We demonstrated this method using Am-Be, Ra(α)-Be, Cf, Pu-Be neutron sources and obtained the successful results which agreed within 1%.

Development of Dynamic Three-Dimensional Multi-Pinhole Gamma Camera Reviewed

Hisato Takemoto, Kenichi Watanabe, Jun Kawarabayashi, Tetsuo Iguchi and Akira Uritani

Vol. 43 ( 4 ) page： 344-347 2006.4

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

In this paper we propose a dynamic 3-D gamma camera consisting of multi-pinhole collimators and flat panel detectors. Through simulation studies on various pinhole configurations we determined that from a spatial and time resolution consideration, pinhole collimators with a 60° opening angle achieved acceptable dynamic 3-D imaging results. With regard to basic system performance, we estimated that the spatial and time resolution exceeds 3.5 mm and 4 s, respectively, for a small animal injected with 99mTc with an activity of 37 MBq. In addition, from further experiments we concluded that the proposed system would be acceptable and practical as a dynamic 3-D imager for nuclear medicine applications although position calibration concerns require further study.

Improvement of Photon Collection Uniformity from an NE213 Scintillator Using a Light Guide Reviewed

H.Harano, T.Matsumoto, Y.Shibata, Y. Ito, A.Uritani, K.Kudo

Nuclear Science, IEEE Transactions on Vol. 52 ( 6 ) page： 3147 - 3150 2005.12

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

The uniformity in collecting scintillation photons to the photomultiplier is one of the key parameters to carry out precise measurement using scintillators. A simple method is proposed to improve the collection uniformity of the scintillation photons just by inserting a light guide between a scintillator and a photomultiplier where the sidewall of the light guide is surrounded by a black paper as a photon absorber. This light guide insertion is expected to have a function to reduce the collection efficiency of the scintillation photons generated closer to the photomultiplier due to the larger transmission loss, since a decrease of the angle of incidence raises the fraction of the photons escaping from the sidewall of the light guide. The experiments using an NE213 liquid organic scintillation detector and gamma-ray sources revealed that the light guide functioned as a compensator for the original tendency of the photon collection and improved the photon collection uniformity. The details of the physical mechanism were examined by simulating the behavior of the gamma rays using the EGS4 electron-photon transport Monte Carlo code and the light propagation process using the ray-tracing program GuideM. The effects of the light guide were also examined on the whole energy resolution and the discrimination capability to separate gamma rays and neutrons.

Fast Neutron Spectrometer Composed of PSPCs and Si(Li)-SSDs with Excellent Energy Rresolution and Detection Efficiency Reviewed

T.Matsumoto, H. Harano, A. Uritani, K.Kudo

IEEE Transactions on Nuclear Science Vol. 52 ( 6 ) page： 2923 - 2926 2005.12

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

We have developed a fast neutron spectrometer composed of three position-sensitive proportional counters (PSPCs) with methane gas and two Si(Li) surface barrier semiconductor detectors (SSDs). A collimated incident neutron beam interacts with hydrogen atoms in the methane gas to generate recoil protons. Position information of the recoil protons obtained from the PSPCs gives the recoil angle. At the same time, the energy of the recoil protons is measured with the three PSPCs and the two SSDs. Finally, the neutron energy is derived using the recoil-proton energy and the recoil angle. This spectrometer was experimentally tested using a monoenergetic neutron beam with energy of 5.0 MeV. The energy resolution and the detection efficiency were 3.5% and 1.1 times10-3 %, respectively. The energy resolution could be achieved better than 2% by selecting events under proper conditions. We also developed a Monte Carlo code to evaluate the characteristics of the spectrometer. The results obtained from these simulations are compared to those obtained through experiments.

中性子検出器の開発動向　―スペクトロメータを中心に―

瓜谷章

放射線 Vol. 31 ( 4 ) page： 273-278 2005.10

Development of Compact Compton Gamma Camera for Non-destructive Detection and Location of Hidden Explosives with Neutron Induced Prompt Gamma-Ray Imaging

T. Iguchi, J. Kawarabayashi, K. Watanabe, H. Kenjyo, A. Uritani

Nuclear Science Symposium Conference Record, 2005 IEEE Vol. 2 page： 735 - 739 2005.10

Language：English

As a unique gamma-ray sensor for detection and location of hidden explosives with neutron induced prompt gamma-ray analysis, we are developing a compact and efficient Compton gamma camera based on stacked BGO scintillator rods to deduce the incident direction of characteristic 10.8 MeV gamma-rays produced from nitrogen abundant in explosives through neutron capture reaction. The detector unit consists of 5.4 mm times; 5.4 mm times 150 mm BGO scintillator rods stacked into an 8times8 array and two multi-anode photomultiplier tubes mounted at the both ends, which can measure three-dimensional position and intensity of scintillations produced through Compton multiple scattering inside the detector and follow the track of scattered gamma-rays backward according to Compton scattering kinematics to estimate the location of a specific energy gamma-ray source without any mechanical collimation. We have designed and constructed the prototype system of 6 detector units with multi-functional ASIC for multichannel signal read-out. The outline and applicability of this system is presented with some preliminary performance tests by using quasi-monochromatic 10.8 MeV gamma-ray beams produced through laser-Compton scattering with the electron storage ring.

Convenient Method of Relative Calibration of the Neutron Source Emission Rate between Ddifferent Source Types

H. Harano, T. Matsumoto, T. Shimoyama, Y. Sato, A. Uritani, Y. Hino, K. Kudo, T. Michikawa

Nuclear Science Symposium Conference Record, 2005 IEEE Vol. 1 page： 524 - 528 2005.10

Language：English

Neutron source emission rates are determined by absolute or relative measurement. The relative measurement is performed by comparing between a sample source and a calibrated reference source of the same type. In this calibration, the energy spectra of the sample and reference sources should be identical, since normally there exists energy dependence in the response of neutron detectors. We propose a method of relative calibration of the neutron source emission rate between different source types and spectra. In the present method, a sample source or a calibrated reference source is located at the center of a graphite pile and thermal neutron flux at a special position is monitored and compared. We performed gold foil activation measurements at the NMIJ/AIST graphite pile and revealed that the thermal neutron flux at that position per unit source emission rate is independent on the types of neutron sources. The details of the physical mechanism were examined by calculating the spectral fluence of the neutrons thermalized inside the graphite pile using the MCNP4C code. We demonstrated this method using Am-Be, Ra(alpha)-Be, Cf, Pu-Be neutron sources and obtained the successful results which agreed within 1%.

Development of a Novel Small-Sized Neutron Detector Based on a ⁶Li-Glass Scintillator

T. Matsumoto, H. Harano, T. Shimoyama, A. Uritani, Y. Sakurai, K. Kudo

Nuclear Science Symposium Conference Record, 2005 IEEE Vol. 3 page： 1291 - 1293 2005.10

Language：English

A small-sized thermal neutron detector based on a 6Li-glass scintillator and a plastic optical fiber was developed for measurement of a dose distribution of thermal neutrons in a thermal-neutron standard field. A contribution of gamma rays can not completely be neglected in the neutron measurement with this detector, although the 6Li-glass scintillator is distinguishable for the neutrons and the gamma rays by difference of each pulse height. Moreover, to reduce an uncertainty of neutron counts caused by the gamma ray background around a discrimination level, we suggested a gamma-ray suppression type of a small-sized thermal neutron detector with a 6Li-glass scintillator, a hollow CsI(Tl) scintillator and plastic optical fibers. The detector can reject signals due to the gamma rays with an anti-coincidence method. In the present paper, we evaluated the gamma-ray suppression ability of the detector using the EGS4 electron-photon transport Monte-Carlo code with the PRESTA routine. As the results, the sufficient gamma-ray suppression effect was shown.

トレーサブルな中性子計測と国際比較 Invited

工藤勝久、瓜谷章、原野英樹、松本哲郎、戸田泰弘

放射線 Vol. 31 ( 2 ) page： 105-110 2005.4

Fast Neutron Spectrometer Composed of Position-Sensitive Proportional Counters and Si(Li)-SSDs with Excellent Energy Resolution and Detection Efficiency

Progress Report Vol. 194/U page： 91 2005.3

Development of Real-time Thermal Neutron Monitor Using Boron-Loaded Plastic Scintillator with Optical Fiber for Boron Neutron Capture Therapy Reviewed

M. Ishikawa, K. Ono, Y. Sakurai, H. Unesaki, A. Uritani, G. Bengua, T. Kobayashi, K. Tanaka ,T. Kosako

Applied Radiation and Isotopes Vol. 61 ( 5 ) page： 775-779 2004.11

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

A new thermal neutron monitor for boron neutron capture therapy was developed in this study. We called this monitor equipped boron-loaded plastic scintillator that uses optical fiber for signal transmission as an [scintillator with optical fiber] SOF detector. A water phantom experiment was performed to verify how the SOF detector compared with conventional method of measuring thermal neutron fluence. Measurements with a single SOF detector yielded indistinguishable signals for thermal neutrons and gamma rays. To account for the gamma ray contribution in the signal recorded by the SOF detector, a paired SOF detector system was employed. This was composed of an SOF detector with boron-loaded scintillator and an SOF detector with a boron-free scintillator. The difference between the recorded counts of these paired SOF detectors was used as the measure of the gamma ray contribution in the measured neutron fluence. The paired SOF detectors were ascertained to be effective in measuring thermal neutron flux in the range above 106 (n/cm2/s).

Development of a Tiny Neutron Probe with an Optical Fiber for BNCT

KURRI Progress Report 2003 page： 133 2004.10

Fast Neutron Spectrometer Composed of Position-Sensitive Proportional Counters and Si(Li)-SSDs with Excellent Energy Resolution and Detection Efficiency

T. Matsumoto, H. Harano, A. Uritani, K. Kudo

Nuclear Science Symposium Conference Record, 2004 IEEE Vol. 2 page： 715 - 719 2004.10

Language：English

We have developed a fast neutron spectrometer composed of three position-sensitive proportional counters (PSPCs) with methane gas and two Si(Li) detectors. A collimated incident neutron interacts with a hydrogen atom in the methane gas to generate a recoil proton. Position information on the recoil proton obtained from the PSPCs gives the recoil angle. At the same time, the energy of the recoil proton is measured with the three PSPCs and the Si(Li) detectors. Finally, the neutron energy is derived using the recoil-proton energy and the recoil angle. This spectrometer was experimentally tested using a monoenergetic neutron beam with energy of 5.0 MeV. The energy resolution and the detection efficiency were 3.5% and 1.1×10-5, respectively. The energy resolution better than 2% could be achieved by selecting events under proper conditions. We also developed a Monte-Carlo code in order to evaluate the characteristics of the spectrometer. The calculation results were compared with the experimental ones.

Improvement of Photon Collection Uniformity from an NE213 Scintillator Using a Light Guide

H. Harano, T. Matsumoto, Y. Shibata, Y. Ito, A. Uritani, K. Kudo

Nuclear Science Symposium Conference Record, 2004 IEEE Vol. 2 page： 841 - 845 2004.10

Language：English

The uniformity in collecting scintillation photons to the photomultiplier is one of the key parameters to carry out precise measurement using scintillators. A simple method is proposed to improve the collection uniformity of the scintillation photons just by inserting a light guide between a scintillator and a photomultiplier where the sidewall of the light guide is surrounded by a black paper as a photon absorber. This light guide insertion is expected to have a function to reduce the collection efficiency of the scintillation photons generated closer to the photomultiplier due to the larger transmission loss, since a decrease of the angle of incidence raises the fraction of the photons escaping from the sidewall of the light guide. The experiments using an NE213 liquid organic scintillation detector and gamma-ray sources revealed that the light guide functioned as a compensator for the original tendency of the photon collection and improved the photon collection uniformity. The details of the physical mechanism were examined by simulating the behavior of the gamma rays using the EGS4 electron-photon transport Monte-Carlo code and the light propagation process using the ray-tracing program GuideM. The effects of the light guide were also examined on the whole energy resolution and the discrimination capability to separate gamma rays and neutrons.

Construction of 144, 565 keV and 5.0 MeV Monoenergetic Neutron Calibration Fields at JAERI Reviewed

Y. Tanimura, M. Yoshizawa, J. Saegusa, S. shimizu, M. Yoshida, Y. shibata, A Uritani, K Kudo

Radiat Protection and Dosimetry Vol. 110 page： 85-89 2004.9

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

Monoenergetic neutron calibration fields of 144, 565 keV and 5.0 MeV have been developed at the Facility of Radiation Standards of JAERI using a 4 MV Pelletron accelerator. The 7Li(p,n)7Be and 2H(d,n)3He reactions are employed for neutron production. The neutron energy was measured by the time-of-flight method with a liquid scintillation detector and calculated with the MCNP-ANT code. A long counter is employed as a neutron monitor because of the flat response. The monitor is set up where the influence of inscattered neutrons from devices and their supporting materials at a calibration point is as small as possible. The calibration coefficients from the monitor counts to the neutron fluence at a calibration point were obtained from the reference fluence measured with the transfer instrument of the primary standard laboratory (AIST), a 24.13 cm Bonner sphere counter. The traceability of the fields to AIST was established through the calibration

Development of a Tiny Neutron Pprobe with an Optical Fibre for BNCT Reviewed

Y. Ito, G. Katano, H. Harano, T. Matsumoto, A. Uritani, K. Kudo, K. Kobayashi, T. Yoshimoto, Y. Sakurai, T. Kobayashi, and C. Mori

Radiat Protection and Dosimetry Vol. 110 ( 1-4 ) page： 619-622 2004.8

Characterization of Gamma Rays Existing in the NMIJ Standard Neutron Field Reviewed

H. Harano, T. Matsumoto, Y. Ito, A. Uritani, and K. Kudo

Radiat Protection and Dosimetry Vol. 110 ( 1-4 ) page： 69-72 2004.8

Development of a Fast Neutron Spectrometer Composed of Silicon-SSD and Position-Sensitive Proportional Counters Reviewed

T. Matsumoto, H. Harano, Y. Ito, A. Uritani, K. Emi, and K. Kudo

Radiat Protection and Dosimetry Vol. 110 ( 1-4 ) page： 223-226 2004.8

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

A new fast neutron spectrometer has been developed. The spectrometer is composed of a silicon surface barrier detector and three position-sensitive proportional counters with methane gas working as counting gas and a radiator. A collimated incident neutron interacts with a hydrogen atom in the methane gas to generate a recoil proton. The position information on the path of the recoil proton obtained from the three position-sensitive proportional counters gives the recoil angle. In the meanwhile, the energy of the recoil protons is measured with the three proportional counters and the silicon surface barrier detector. The characteristics of the spectrometer were evaluated with a monoenergetic neutron beam. The best energy resolution was 1.8% for 5.0 MeV neutrons.

DOI： 10.1093/rpd/nch125

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