DOI： 10.1016/j.nima.2022.167636

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Language：Japanese  

DOI： 10.35848/1347-4065/ac971e

Web of Science

Language：Japanese  

DOI： 10.1016/j.nima.2022.167414

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DOI： 10.1016/j.nima.2022.167140

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Language：Japanese  

Language：Japanese  

DOI： 10.1007/s10854-022-08843-0

Web of Science

DOI： 10.3390/jne3030012

Web of Science

Language：Japanese  

DOI： 10.1585/pfr.17.2405096

Web of Science

Language：Japanese  

DOI： 10.1080/00223131.2021.2017372

Web of Science

Language：Japanese  

DOI： 10.1016/j.nima.2022.166793

Web of Science

Language：Japanese  

DOI： 10.35848/1347-4065/ac7273

Web of Science

Language：Japanese  

DOI： 10.1585/pfr.17.2405045

Web of Science

Language：Japanese  

DOI： 10.1080/00223131.2021.1996297

Web of Science

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DOI： 10.1080/00223131.2021.1981475

Web of Science

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DOI： 10.35848/1347-4065/ac5153

Web of Science

Language：Japanese  

DOI： 10.1016/j.nima.2021.166074

Web of Science

Language：Japanese  

DOI： 10.35848/1347-4065/ac3524

Web of Science

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

DOI： 10.11269/jjrsm.20.45

Language：Japanese  

DOI： 10.1585/pfr.16.1405104

Web of Science

Language：Japanese  

DOI： 10.1115/1.4048841

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Language：Japanese  

Language：Japanese  

DOI： 10.1016/j.nima.2021.165151

Web of Science

Language：Japanese  

DOI： 10.1088/1748-0221/16/04/P04016

Web of Science

Language：Japanese  

DOI： 10.1016/j.apradiso.2020.109553

Web of Science

PubMed

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

The Pulse shape discrimination (PSD) technique for single crystal CVD diamond detector (SDD) was applied to
the real-time thermal neutron measurement during the 3rd campaign of Deuterium-Deuterium (D-D) plasma
experiment in the Large Helical Device (LHD). The PSD method is based upon the different shape of electrical
pulses produced in diamond by gamma-ray (triangular-shaped pulse) and energetic ions (rectangular-shaped
pulse), respectively. An improved PSD was developed which makes use of the full width at half maximum
(FWHM) and the full width at 2/3 of the peak height (FW2/3 PH). These two parameters reflect the difference in
the pulse shape produced by gamma-rays and energetic ions.
The performance of this improved PSD technique was first tested irradiating the SDD by gamma-rays from
60Co and alphas from 241Am radiation sources, respectively. Then, using a 6LiF thermal neutron converter, a
successful discrimination between gamma-rays and alpha particles and tritons generated by the 6Li(n,α)3H re-
action induced by neutrons from 252Cf spontaneous fission neutron source was achieved. Thanks to this PSD
processing technique, the thermal neutron detection efficiency increased about 1.7 times compared to previous
measurements performed without the PSD technique.
The real-time thermal neutron measurement by SDD with this enhanced PSD processing was also used during
D-D plasma discharges in the Large Helical Device (LHD). It was found that both the time integrated counts and
the time evolution count rate measured by the SDD reproduced well that of the fission chamber used as official
LHD neutron monitor. The capability of the SDD detector using the PSD technique of precise real-time thermal
neutron measurement in LHD was demonstrated.

DOI： 10.1016/j.fusengdes.2020.112063

Web of Science

Language：English   Publishing type：Research paper (international conference proceedings)  

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

DOI： 10.1088/1741-4326/ab90c9

Web of Science

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

The development of a neutron detector for real-time measurements in an intense neutron field is desired. We are developing a quartz optical-fiber-based neutron detector as a real-time neutron monitor. Thus far, Eu:LiCaAlF6 crystals and LiF/Eu:CaF2 eutectics were used as the scintillators of the quartz optical-fiber-based neutron detectors. These scintillators have high light yields, but relatively long decay time constants, which are limitation factors of the dynamic range of optical-fiber-based neutron detectors. In this paper, we applied a small Li-glass scintillator to a quartz optical-fiber-based neutron detector using an optical fiber with high numerical aperture (NA) and a UV-curable resin with high transmittance. The fabricated detector showed a clear peak corresponding to neutron events in the pulse height distribution. The radiation resistance was evaluated and no deterioration was observed up to 2×1012 n/cm2. The detector output linearity was confirmed up to 450 kcps, which was about ten times larger than that of the detector using the conventional Eu:LiCaAlF6 or LiF/Eu:CaF2 scintillator.

DOI： doi.org/10.18494/SAM.2020.2748

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

DOI： 10.1016/j.radmeas.2020.106270

Web of Science

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

The Nagoya University Accelerator driven Neutron Source (NUANS) is constructed at the main campus of the Nagoya University. The electrostatic accelerator is used with the maximum proton energy and intensity of 2.8MeV, 15mA(42kW) respectively. Two neutron beamlines are designed at NUANS. The BL1 is dedicated to BNCT development. The BL2 is designed for research and development for neutron devices and neutron imaging. The neutrons used for the BL2 are generated by using the (p, n) reaction from a thin beryllium target. We constructed a compact target station for the BL2 and measured the neutron transmission image.

DOI： 10.1051/epjconf/202023105002

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

DOI： 10.1016/j.nima.2018.11.120

Web of Science

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

DOI： 10.1016/j.nima.2018.09.079

Web of Science

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

高等学校などで使用されているクルックス管は，一般的に漏洩Ｘ線を発生している。Ｘ線の線量率の測定に，これらの学校が保有している箔検電器を使う方法を提案した。箔検電器の箔の開き角は電極に与えられた電位に依存して変化する。この電位はＸ線によって空気中に作られたイオンを集めて減少し箔は閉じて行く。しかし，空気中のイオン密度は周辺の電位や風，および箔検電器に荷電する電荷の正負の影響も受ける。正電荷を荷電した場合に箔が閉じる時間と負電荷を荷電した場合のそれとの幾何平均値をとることによって，電離箱で測定した線量率との間に再現性のある関係を得ることができた。この関係を校正線と呼ぶが，他の同様の市販の箔検電器にも適用できる。

DOI： 0.3769/radioisotopes.69.1

Language：Japanese  

DOI： 10.18494/SAM.2020.2748

Web of Science

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

In the Large Helical Device (LHD) of the National Institute for Fusion Science, a deuterium plasma experiment was performed in March 2017. Neutrons with an energy of 2.45 MeV are generated by d (d, n) 3He reactions. The evaluation of this neutron flux in the torus hall, as well as within the LHD vessel, is very important for the decommissioning of the LHD in the future and the radiation shielding for workers and components around the LHD. In this study, we evaluate the spatial distribution of thermal and epithermal neutron flux on the floor level of the LHD torus hall by measuring the neutron activation of gold foils. The flux information obtained in the experiment can be used for the evaluation of radio-activation and the shielding design.

DOI： 10.1585/pfr.14.340516

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

DOI： 227-232

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

DOI： 221-226

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

DOI： 214-220

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

DOI： 207-213

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

DOI： https://doi.org/10.1088/1748-0221/14/09/C09039

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

In the Large Helical Device (LHD) of the National Institute for Fusion Science, the experiments using deuterium plasma were performed from March 2017. Neutrons with the energy of 2.45 MeV are generated by d (d, n) 3He reactions. The evaluation of the neutron flux in the torus hall as well as the LHD vessel is very important for designing the decommissioning of the LHD in the future, and the radiation shielding for workers and components around LHD. In this study, we performed the activation experiments using multiple activation foils to obtain a neutron spectrum in the vacuum vessel of the LHD. The reaction rate of each activation foil was generally consistent with the calculation result by MCNP6. As a result of the unfolding with SAND-II code, we experimentally obtained the neutron spectrum in the vacuum vessel of the LHD for the first time.

DOI： 10.1016/j.fusengdes.2019.01.005

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Language：Japanese  

DOI： 10.1088/1748-0221/14/09/C09039

Web of Science

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

We developed a thermal neutron source for performance tests of boron agents for
Boron Neutron Capture Therapy (BNCT) at Neutron exposure Accelerator System for Biological
Effect Experiments (NASBEE) in National Institute of Radiological Sciences, Japan. The thermal
neutron flux at the experimental position was measured to be 2:18 108 ncm2s, the cadmium
ratio was 9:21, and gamma ray dose rate was 2:11 Gyh. The neutron dose rate was estimated to be
2:96 Gyh. These values indicate that the neutron source can be applicable for tests of boron agents
although application range is limited. An example of irradiation experiment is described.

DOI： 10.1088/1748-0221/14/06/T06010

Web of Science

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

We have developed the single sphere neutron spectrometer with five sensitive layers using the TRUST Eu:LiCAF scintillator and the WLSF readout. We evaluated the energy dependence of the detector response at thermal neutron and 24 keV, 144 keV, 565 keV, 5MeV and 14.8 MeV mono-energetic neutron irradiation fields. The experimentally determined neutron sensitivities are consistent with the Monte Carlo calculations. The detector responses for a bare and a heavy-water moderated 252Cf sources also show good agreement with the expected ones using the Monte Carlo calculations.

DOI： 10.15669/pnst.6.122

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

We fabricated the hybrid type optical fiber based dosimeter system using Eu:BaFBr and Ce:CaF2 optically stimulated luminescence (OSL) materials in order to correct the quenching effect under high LET particle irradiation. The fabricated dosimeter probe can obtain signals from both OSL materials through one optical fiber. We investigated the probe response by irradiating it with mono-energetic carbon ions and broad-spectrum ones making the spread-out Bragg peak (SOBP). We demonstrated that the SOBP shape can be improved by correction of the quenching effect using the relationship between the luminescence efficiency and the signal intensity ratio of both OSL materials.

DOI： 10.15669/pnst.6.238

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

We fabricated a wide one-dimensional X-ray line sensor in backscatter X-ray imaging system. The length and width of the sensitive area of our line sensor is 200 mm and 50 mm, respectively. By using fan-beam X-rays and scanning in the perpendicular direction to the fan-beam plane, two-dimensional backscatter X-ray images can be obtained. In basic experiments, we confirmed that an iron rod placed at the depth of, at least, 9 cm in a concrete brock can be seen by combining our line sensor and C-band linac X-ray generator.

DOI： 10.15669/pnst.6.208

DOI： 10.1585/pfr.14.3405162

Web of Science

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

The Kyoto University electron linac, KURRI-LINAC, has been used for executing a project to develop methodology for the integrity evaluation of nuclear fuels, named the N-DeMAIN (Development of Non-Destructive Methods Adapted for Integrity test of Next generation nuclear fuels) project in Japan. As a non-destructive method, the neutron resonance transmission analysis was adopted for the identification and the quantification of nuclide in the fuels. Furthermore, determination of temperature distribution in the fuels based on Doppler broadening was also planned as well as traditional transmission imaging.
A target-moderator-reflector system (TMRS) and a beam collimator system has been redesigned to obtain the highest intensity with the use of simulation calculation. The neutron beam line is placed at an angle of 135° with respect to the electron beam line. Optimal arrangement of the target and the moderator was investigated. After then, collimator design was performed, and a collimator system to shape the neutron and γ ray beams was designed. Test experiments were performed by using this system.
Here, we explain the results of design study of the TMRS and the collimator, and the test experiments.

DOI： doi.org/10.1016/j.physb.2018.06.009

DOI： 10.1016/j.physb.2018.06.009

Web of Science

Language：Japanese  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.7566/JPSCP.22.011024

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.7566/JPSCP.22.011003

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We developed a one-dimensional position-sensitive neutron detector using Transparent RUbber SheeT type Eu:LiCaAlF6 (TRUST Eu:LiCAF) scintillators and a newly proposed wavelength-shifting fiber (WLSF) readout. The proposed position-sensitive WLSF readout consists of a number of WLSFs optically divided to distinguish the scintillation position. We experimentally compared the position sensitivities of the optically divided WLSF type detector and a conventional one using light attenuation in the WLSFs. We concluded that the proposed detector had higher spatial resolution than that of the conventional one. Additionally, we fabricated a prototype version of the optically divided WLSF type detector. We determined the prototype detector had a relative spatial resolution of approximately 20 %.

DOI： 10.7566/JPSCP.22.011020

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

An accelerator-driven compact neutron source for boron neutron capture therapy (BNCT) has been developed in Nagoya University since 2013. A Dynamitron accelerator and a Li target are used to generate neutrons. The 7Li(p, n)7Be nuclear reaction produces neutrons. Since the generated neutrons have considerably high energy, up to one MeV, it is necessary to lower the neutron energy to an epithermal region that is suitable for BNCT. In this work, we have designed a beam shaping assembly (BSA) that lowers the neutron energy and makes beam-like neutrons. The BSA consists of a MgF2 moderator, a lead reflector, a radiation shield and a neutron collimator. The PHITS (Ver.2.66) code has been used to simulate the neutron transport in the BSA. This paper mainly describes two issues. One is the optimization of the shape of the BSA, mainly the moderator, and the other is the dependence of the simulation results on the nuclear data libraries, JENDL-4.0 and ENDF/B-VII.1.

DOI： 10.7566/JPSCP.22.011002

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

The deuterium operation of the large helical device (LHD) began in March 7, 2017, after long-term preparation and commissioning of apparatuses necessary for execution of the deuterium experiment. A comprehensive set of neutron diagnostics was developed and installed onto LHD through numerous efforts in preparation. Neutron diagnostics play an essential role in both neutron yield management for the radiation safety and extension of energetic-particle physics study in LHD. Neutron flux monitor (NFM) characterized by fast-response and wide dynamic range capabilities is successfully working. Total neutron emission rate reached 3.3×10¹⁵(n/s) in the first deuterium campaign of LHD. The highest neutron emission rate was recorded in inward shifted configuration. Neutron yield evaluated by neutron activation system agrees with neutron yield measured with NFM. Performance of vertical neutron camera was demonstrated. Neutron emission profile was inwardly shifted in the inwardly shifted configuration, whereas it was outwardly shifted in the outwardly configuration. Secondary deuterium-tritium neutrons produced by triton burnup in LHD deuterium plasmas were detected for the first time in stellarator/heliotron devices in the world. Similar to total neutron emission rate, the inward shifted configuration provided highest triton burnup ratio.

DOI： 10.1109/TPS.2018.2836987

Web of Science

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

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

In situ calibration of the neutron activation system on the Large Helical Device (LHD) was performed by using an intense ²⁵²Cf neutron source. To simulate a ring-shaped neutron source, we installed a railway inside the LHD vacuum vessel and made a train loaded with the ²⁵²Cf source run along a typical magnetic axis position. Three activation capsules loaded with thirty pieces of indium foil-stacked with total mass of approximately 18 g were prepared. Each capsule was irradiated over 15 hours while the train was circulating. The activation response coefficient (9.4 ± 1.2)×10^-8 of ¹¹⁵In(n, n')^115mIn reaction obtained from the experiment is in good agreement with results by three-dimensional neutron transport calculations using the MCNP 6 code. The activation response coefficients for 2.45 MeV birth neutron and secondary 14.1 MeV neutron from deuterium plasma were evaluated from the activation response coefficient obtained in this calibration experiment.

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

DOI： 10.1016/j.radmeas.2017.03.043

Web of Science

DOI： 10.1063/1.5009475

Web of Science

PubMed

Language：Japanese  

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

To accurately estimate an actual dose during radiotherapy treatment, dosimeters are required to be inserted into the affected region in a patient's body. Therefore, we are developing a small size dosimeter consisting of optical fibers and optically stimulated luminescence (OSL) elements. We fabricated two types of small size dosimeters using Eu:BaFBr and Ce:CaF₂. We measured the Bragg peak of high energy carbon ions in a water equivalent material. OSL materials showed the quenching effect when irradiated by high linear energy transfer (LET) particles. The sensitivity of Eu:BaFBr and Ce:CaF₂ monotonically decreased with different coefficients. The ratio of the signal intensity of these two OSL materials can uniquely determine the sensitivity of each OSL material. We corrected the quenching effect of the OSL dosimeters in the spread out Bragg peak with this relationship.

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

DOI： 10.18494/SAM.2017.1626

Web of Science

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

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

Language：Japanese  

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

We fabricated a small size optical fiber type dosimeter system using Ce:CaF₂ OSL element. We evaluated basic response of fabricated dosimeter to radiations of X-ray and high-energy carbon ions. When irradiating X-ray, good linearity can be confirmed. With increasing linear energy transfer (LET) of carbon ions, luminescence efficiency of Ce:CaF₂ decreases. Compared with the conventional small dosimeter using Eu:BaFBr OSL element, Ce:CaF₂ shows a small deterioration in the luminescence efficiency.

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

We fabricated the prototype of a single sphere neutron spectrometer with five sensitive layers using the Transparent FUbber SheeT Eu:LiCaAlF₆ (TRUST Eu:LiCAF) scintillator and the wavelength-shifting fibers (WLSFs). We confirmed that the fabricated detector shows a clear neutron peak and can discriminate neutron and gamma-ray events in signal pulse height spectra. We additionally compared the neutron sensitivity between the new TRUST Eu:LiCAF type and the previous LiF-ZnS mixed powder type. The sensitivity of the new one is 40 times higher than that of the previous one.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.7566/JPSCP.11.030005

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

As an alternative to the standard 3He neutron detector, we are developing the Transparent RUbber SheeT type (TRUST)Eu doped LiCaAlF6 (Eu:LiCAF)scintillator. This type of neutron scintillator can easily be fabricated as a large area sheet. In order to take advantage of a large area detector, we try to read out scintillation photons using a wavelength-shifting fiber (WLSF) from a TRUSTEu:LiCAF scintillator. The TRUST Eu:LiCAF scintillator with the size of 50x50x5 mm3 was mounted on the WLSF plate and the end of the WLSFs was connected with a PMT. In order to reject high pulse height events induced in the WLSFs, we applied the pulse shape discrimination technique. The gamma-ray intrinsic and neutron
absolute detection efficiency is evaluated to be 8.8x10^7 and 9x103 cps/ng Cf(2m) for the TRUSTEu:
LiCAF scintillator with the size of 50x50x5 mm^3.

Language：Japanese  

There are more than 700 thousand road bridges, whose lengths are longer than 2 m. Sixteen percent of them were built more than 50 years ago, and their fraction will increase to 40% and 65%, in next 10 years and 20 years, respectively. The maintenance, inspection and repair of them are managed mainly by a local government, which the infrastructures are located. However, the management of the infrastructure is becoming more difficult for the local governments, because of the lack of a financial resource, human resource, and technical knowledge. In Japan, the deterioration of the infrastructures by the sea wind and the salt is serious especially for the roadbed and the reinforced concrete due to the corrosion. Nondestructive inspection methods, which are currently being applied on-site are not enough to measure the degree of damage of concretes, quantitatively. So, a novel method for nondestructive inspection of inner structure of concrete with radiation instrumentation and electron accelerator, which uses X-ray backscatter is being developed. The X-ray backscatter system, which has advantages in highly precise image and one-sided accessibility in inspection, is developed for use in inspecting roadbed and bridge, as a compact and light-weight system. Nondestructive inspection by visualization, using a high resolution X-ray backscatter image for reinforcement bar and a pot-hole inside concrete structure will be possible.

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

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

We fabricated a prototype portable neutron detector using a Ce:LiCaAlF₆ (Ce:LiCAF) scintillator and evaluated its basic performance. The weight of the fabricated detector including the battery is 800 g, significantly less than that of the conventional portable neutron detector, which weighs more than 5 kg. The neutron sensitivity of the fabricated detector is evaluated to be 2.3 cps/(mu Sv/h), comparable to that of the conventional detector. The gamma-ray intrinsic detection efficiency is evaluated to be less than 10(-6). The gamma-ray sensitivity is sufficiently low under ordinary circumstances. The expected count rate of the error counting due to the pile-up effect of gamma-ray-induced events is confirmed to be less than the background count rate for an incident gamma-ray rate of less than 10(4) gammas/s.

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

DOI： 00

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

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

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

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

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.

Language：Japanese  

Authorship：Lead author   Language：Japanese  

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

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

DOI： 10.1016/j.jlumin.2013.07.016

Authorship：Lead author   Language：Japanese  

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.

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.

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.

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

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

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

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

DOI： 10.1093/rpd/nct029

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

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.

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.

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

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.

Authorship：Lead author   Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (bulletin of university, research institution)  

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

We propose a novel electron density imaging technique based on a Compton scattered X-ray CT (CSX-CT)
technique. We design fundamental configuration of the CSX-CT system, which consists of a fan-shaped
X-ray beam, two-dimensional sensors for scattered X-ray detection, parallel plate collimators for limitation of the direction of scattered X-rays and a line sensor for the transmission of X-ray CT
(TX-CT). An image obtained by the TX-CT can be used to correct the attenuation effect of scattered X-rays.
Through Monte Carlo simulation modeling studies of the CSX-CT system, we demonstrate that the
utilization of the information of scattered X-rays is useful to obtain the electron density image. We
additionally confirm that the medical exposure irradiated in the CSX-CT is estimated to be lower than the maximum dose recommended in the guideline of some committees.

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

We demonstrate neutron-gamma discrimination based on a pulse shape discrimination method in a Ce:LiCAF scintillator. We have tried neutron-gamma discrimination using a difference in the pulse shape or the decay time of the scintillation light pulse. The decay time is converted into the rise time through an integrating circuit. A 252Cf enclosed in a polyethylene container is used as the source of thermal neutrons and prompt gamma-rays. Obvious separation of neutron and gamma-ray events is achieved using the information of the rise time of the scintillation light pulse. In the separated neutron spectrum, the gamma-ray events are effectively suppressed with little loss of neutron events. The pulse shape discrimination is confirmed to be useful to detect neutrons with the Ce:LiCAF scintillator under an intense high-energy gamma-ray condition.

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

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

Long counters are widely used as neutron fluence monitors for their flat response. However, a bulky neutron moderator is required to achieve the flat response, which can be a disadvantage for portability and an undesirable source of scattered neutrons. Reducing the size of the moderator degrades the flat response, especially for high-energy neutrons. We propose a new method to reduce the size of the moderator while keeping a flat response, and we develop a compact flat-response neutron detector. The detector consists of two small spherical $^{3}$ He proportional counters embedded at appropriate positions in a compact cylindrical polyethylene moderator. The sensitivity ratio between the two counters was adjusted to provide a flat response in the total outputs from the two counters. We demonstrated by MCNPX calculations and response measurements for Cf and Am-Be neutrons and monoenergetic neutrons that the present detector had a sensitivity comparable to long counters with a good flat response in a wide energy range up to 20 MeV while being only one-fifth of the weight of long counters. The positions of the effective center were determined as a function of neutron energy. We also proposed a method to evaluate the neutron energy using the detector, which will allow various new applications taking advantage of the ability to measure neutron fluence and energy at the same time.

DOI： 10.1109/TNS.2011.2163191

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

We propose a novel neutron detector that realized flat-response using information of a spatial
distribution of thermal neutrons in a moderator. The proposed detector consists of a 3He position sensitive proportional counter(PSPC) and a cylindrical moderator surrounding the 3He PSPC. The
cylindrical detector is irradiated by neutrons along the cylinder axis. The spatial response of the 3He
PSPC is used to correct the detector response in to flat-response. We adopt a weighting method to
achieve flat-response, in which detected neutrons weighted depending on their detected positions are
accumulated as the detector response. Through Monte Carlo simulation studies, we confirm that the
flat-response neutron detector can be realized by correcting the response of the proposed detector
using the weights determined by a multiple least squar emethod (MLSM). Additionally, fundamental
property of the 3He PSPC is experimentally investigated to check applicability to the proposed flat-response neutron detector. We conclude that we should take account of the end effect when
determining the weights and correcting the detector response.

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

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

Neutron monitoring is quite important because neutron yield generated by fusion reactions corresponds to
the fusion output. In design of the neutron monitor, Monte Carlo simulations play an important role to make
corrections on various parameters, such as neutron energy spectrum and spatial distribution when determining the calibration constant. We consider the calibration procedures using a Cf point source toroidally rotating in the vacuum vessel, and evaluate uncertainties of the calibration constant for the neutron detector placed on the center
axis.

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

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

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

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

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

We have developed a thermal neutron calibration method using a reactor produced neutron beam in JRR-3M of the Japan Atomic Energy Agency. Neutron-induced prompt gamma ray analysis has usually been performed in this beam line. Neutron energy distributions with negligible contributions from epithermal neutrons were measured by a time-of-flight method with a chopper made of 6LiF powder. The thermal neutron flux was determined by a gold foil activation method. We found that the thermal neutron beam in JRR-3M was well suited for calibration, neutron detector development or neutron dosimetry.

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

Neutron monitoring is quite important because fusion neutrons are a direct evidence of fusion reactions. In calibration experiments of a neutron monitoring system, Monte Carlo calculations play an important role to correct various effects. To perform Monte Carlo calculations for a helical type fusion device, we make a program that can automatically generate an input file of a helical coil geometry for the MCNP code. The neutron spatial distributions and spectra for the helical devices are calculated in the geometries automatically generated by this program. We also discuss in calibration experiments.

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

Deuterium experiment on the Large Helical Device LHD is now being planned at the National Institute for Fusion Science. The fusion product diagnostics systems currently considered for installation on LHD are described in this paper. The systems will include a time-resolved neutron yield monitor based on neutron gas counters, a time-integrated neutron yield monitor based on activation techniques, a multicollimator scintillation detector array for diagnosing spatial distribution of neutron emission rate, 2.5 MeV neutron spectrometer, 14 MeV neutron counter, and prompt -ray diagnostics.

Language：Japanese  

Language：Japanese  

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

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.

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.

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%.

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.

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.

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.

Authorship：Lead author   Language：Japanese  

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.

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%.

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.

Language：Japanese  

国際度量衡局が主催して行った単色エネルギー中性子フルエンスの国際比較について述べた。本論文では144keVと5.0MeVの２点について紹介しているが、日本の中性子フルエンス標準が、他国のそれと同等性を有していることを示した。

Language：English  

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).

Language：English  

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.

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.

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

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

Language：Japanese  

産総研の電子蓄積リングTERASは760MeVの定常運転による放射光の他に、円偏光放射光やレーザー逆コンプトンγ線源としても利用されている。TERASにおいて、ここ一年間に行ったKickerやRF等の機器改良による蓄積電流量の向上、電子ビーム安定化、放射光利用環境の改善点、及び放射光利用による各研究成果等について報告する。

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

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

Authorship：Lead author   Language：Japanese  

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

The gas multiplication distributions along the anode wires of 3He proportional counters with different sensitive lengths of 10, 15 and 20 cm were measured using a collimated thermal neutron beam at the Kyoto University Reactor facility. The ideal response function excluding the effect of electric field distortion near the boundaries of the anode wire was derived by taking into account the difference between pulse height spectra measured by two different length counters. The pulse height spectrum calculated by the NRESPG Monte Carlo code assuming the ideal gas multiplication region showed relatively good agreement with the response function derived from the measurements. Both the energy resolution of the full energy peak at 764 keV and the peak ratio to the entire pulse height spectrum were improved markedly.

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

Language：English  

Language：English  

We proposed a new micro-calorimetric detector with four single electron transistor (SET) read-out circuits that aimed the real-time detector with spatial resolution of 100 nm. The new detector consists of two layers of the micro-calorimeters. The top layer had four SETs, which worked as thermometers to decide the photoelectron position by the difference of each SET's temperature caused by heat flow in the layer. We investigated the SET performance and the heat flow in the substrate at cryogenic temperature. From calculational results, the temperature resolution of 10 mK could be achieved with a pico-ammeter having 5.0 × 10-9S sensitivity. Also, the detector configuration achieving the 100 nm spatial and 8 μ second time resolution was successfully designed.

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

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

We have developed a novel multi-pinhole-type gamma camera for imaging low-energy gamma-ray emitters. The gamma camera consists of Imaging Plates (IPs) and multi-pinhole collimators made of a lead plate with many pinholes in lattice arrangement. The three-dimensional spatial distribution of a gamma-ray source is reconstructed by using a stereoscopic back-projection technique, where the directions of gamma-ray incidence are determined with the digitized two-dimensional images on the IPs and the configuration of the multi-pinhole collimators. The horizontal and vertical spatial resolutions for a point-like 57Co source evaluated with simulations are 1.5 and 2.5 mm, respectively.

Language：English  

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

設置以来使用してきた稼動心臓部でもあるチャージング用ペレット・チェーンのナイロン部品の劣化による事故などを懸念していたが、予算面から4年越しで少しずつ買い揃えて4本分のチェーンが揃ったので昨年5月に交換に至った。当所の加速器は直流ビーム電流150μA (H+ Beam)の大電流仕様であり、４本のチャージング・チェーンを持っている。　今回の報告は、チャージング・チェーン交換に伴うトラブル発生と加速器のエネルギー安定性について報告する。

Language：Japanese  

常のプラスチック光ファイバーにおいても放射線との相互作用で微弱シンチレーション光が発生することに着目し、これを用いることにより測定可能距離を大幅に延ばすとともに、その低検出効率を逆に活かして、より高フラックス下における放射線分布測定への適用可能性を検討した。その結果、これまでのシンチレーションファイバーを用いた場合に比べ、測定可能距離を約二桁のばすことできた。また、原子炉周辺や加速器、核融合実験装置環境等における放射線モニタリングへの適用の可能性を示した。また、ファイバー出力に対する分光学的片側読み出し手法を新規に考案し、その基本原理の有効性を実証した。

Language：Japanese  

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

Language：English  

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

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

The purpose of this study is to develop a radiation distribution monitor using a normal plastic optical fiber. The monitor has a long operating length and can obtain continuous radiation distributions. A principle of the position sensing is based on a time-of-flight technique. The monitor is sensitive to beta rays or charged particles, gamma rays, and fast neutrons. The spatial resolutions for beta-rays ( 90Sr-90Y), gamma-rays (137Cs), and D-T neutrons are 30, 37, and 13 cm, respectively. The detection efficiencies for the beta-rays, gamma-rays, and D-T neutrons are 0.11%, 1.6×10 -5% and 1.2×10-4%, respectively. The effective attenuation length of the detection efficiency is 18 m. In this paper, we describe the basic characteristics of this monitor.

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

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

Numerical analyzes on individual pulses from a cylindrical 3 He gas ionization chamber have been performed. A radial distribution of the electron ion pairs was successfully analyzed by a deconvolution technique combined with a digital waveform analysis. From the charge distribution, clear separation of events of the reactions of 3He(n,p)T and 3He(n,n)3He at the energy region of the 3He recoil edge was observed.

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

The application of a `digital-analog hybrid signal processing system' combined with a Euclidian distance method is presented. The proposed method is used to improve gamma-ray energy spectrum characteristics of a CdZnTe semiconductor detector. A digital and an analog system are simultaneously applied to the detector output after passing through a preamplifier, where the digital system digitizes the signal pulse shape for the Euclidian distance determination, while the analog system measures the signal pulse height with a conventional analog method. In this paper, the digital and the analog data are combined to improve the energy spectrum characteristics; giving the increase of the photopeak area, the peak-to-valley ratio, and the photopeak sharpness.

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

We present a study on pulse shapes of a CdZnTe semiconductor detector for beta particles and gamma-rays emitted by a 137Cs-90Sr mixed source. When beta and gamma radiations enter a semiconductor detector, two kinds of pulses are produced according to the type of radiations. The characteristics of the pulses are determined by their energy and depth of interaction. The energy deposited on the detector basically determines the pulse height and the depth of interaction affects the pulse shape. Because of the different characteristics of beta and gamma radiations, their pulse shapes are also different. The digital-analog hybrid signal processing method was applied to separation of the beta spectrum from the beta-gamma mixed one. The separation of beta spectrum was done based on a neural network algorithm, a leading edge area method, and a falling continuum tail value method. However, the perfect separation could not be obtained. The separation was also done by reconstructing the spectra on the basis of subtraction of gamma-ray component. The spectra of beta particles and gamma-rays from 137Cs-90Sr mixed source could be separated well by using the reconstruction method.

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

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

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

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

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

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

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

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

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English  

Numerical analyses on individual pulses from a cylindrical 3 He gas ionization chamber have been performed. A radial distribution of the electron ion pairs was successfully analyzed by a deconvolution technique combined with a digital waveform analysis. From the charge distribution, clear separation of events of the reactions of 3He(n,p)T and 3He(n,n)3He at the energy range of the 3He recoil edge was observed.

Language：English  

The purpose of this study is to develop a radiation distribution monitor using a normal plastic optical fiber. The monitor has a long operating length and can obtain continuous radiation distributions. A principle of;the position sensing is based on a time-of-flight technique. The monitor is sensitive to beta rays or charged particles, gamma rays, and fast neutrons. The spatial resolutions for beta rays ( 90Sr-90Y), gamma rays (137Cs) and D-T neutrons are 30 cm, 37 cm and 13 cm, respectively. The detection efficiencies for the beta rays, the gamma rays and D-T neutrons are 0.11%, 1.6×10-5% and 1.2×10-4%, respectively. The effective attenuation length of the detection efficiency is 18 m. In this paper, we describe the basic characteristics of this monitor.

Language：English  

A new concept of compact neutron camera with directional neutron detector arrays is proposed for nuclear fusion experiment. The basic performance of the directional neutron detector is made clear through experiment for a prototype detector with 14 MeV neutrons and design consideration of the detector specification to optimize its directionality. The results show that the angle resolution defined as a full width of neutron incident angles at a half maximum of detector counts would reach up to around 4 degrees at minimum around 45 degrees neutron incidence to the detector axis. The concept for a compact neutron camera is also given by making good use of an array of the optimized directional neutron detectors.

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We present a new application of a `Fusion Method' to improve gamma-ray energy spectrum characteristics of a CdZnTe semiconductor detector. A digital and an analog system are simultaneously applied for the detector output; The digital system digitizes the signal pulse shapes for pattern recognition based on a neural network algorithm. The analog measures the signal pulse heights with a conventional analog system. The digital and the analog output data are fused and then used for improvement of the energy spectrum characteristics, i.e. the photopeak area, the peak-to-valley ratio, and the FWHM of photopeaks.

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A new pulse shape recognition method with multi-shaping amplifiers, combined with a neural network algorithm, has been developed, where four pulse heights are sampled from one signal pulse through four linear amplifiers with different shaping time constants. The four pulse heights are used as characteristic parameters to recognize the pulse shape with a neural network. This method has been applied to signal processing for a CdZnTe semiconductor detector to improve the deteriorated energy spectra caused by pulse height deficits due to the different mobilities of electrons and holes in the detector. The neural network recognizes the pulse shape patterns and provides the corrective magnification factors of the pulse heights. After the corrective procedure, the energy spectrum for 137Cs gamma-rays is improved from 9.3 keV to 7.4 keV in the energy resolution (FWHM) of the 662 keV gamma rays photopeak. The photopeak becomes a considerably symmetrical shape without a low-energy tail. It has been verified that this method is simple and useful for pulse shape analyses, which can be used for many other applications.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The spatial dependence of thermal and fast neutron flux was measured axially in the core of a 1 MW research reactor. The measurements were made by a thin optical fibre detector with a neutron sensitive ZnS(Ag) scintillation tip. For thermal neutrons 6Li was used, whereas for fast neutrons 232Th was used as neutron converter. The spatial dependence was measured by moving the fibre axially with a uniform speed. The measurement takes a few minutes, compared to up to 10 h with the conventional wire activation method. Comparison with traditional measurements shows a good agreement.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A novel neutron detector has been developed to measure energy spectra of space neutrons in a spaceship. The detector consists of a spherical polyethylene moderator with a diameter of 30 cm and 19 pairs of 6Li- and 7Li-glass scintillators arranged along the orthogonal x-, y-, and z-axes of the sphere. The pairs can distinctively detect thermal neutrons in some radiation fields, where other radiation exists, by subtracting the number of detected events of the 7Li-glass scintillator from that of the 6Li-glass one. Hence the detector can clearly obtain the thermal neutron flux distribution in the spherical moderator even in such fields. The detector was applied to the measurement of monoenergetic and 252Cf neutrons. The characteristics of the detector were studied by comparison with the simulations.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Time-spatial neutron measurement was carried out by using a position-sensitive 3He proportional counter (PSPC) in the Kyoto University Critical Assembly. The data of the output pulses from the PSPC were acquired by a data acquisition system which was based on the LN-9000 system of Laboratory Equipment Corporation. In this system, the time and the position data of the neutron detection pulses were simultaneously accumulated by a personal computer. In the present study, the Rossi-α method, which was derived for time-domain neutron correlation analysis, was extended in order to process the measured two-dimensional data of time and space. The processed experimental results and a theoretical formula based on the one-group diffusion approximation neglecting the higher modes agreed well with each other, which indicates the present system is applicable for reactor physics experiments including reactor kinetics.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

On the tip of an optical fiber, a very small amount of ZnS(Ag) scintillator mixed with neutron converter and adhesive paste was painted, which can be inserted into a narrow space and moved by a fiber-driving unit controlled with a personal computer. The presented method made it possible to measure neutron flux distributions in critical assemblies, research reactors or other neutron facilities with position resolution of less than 1 mm and in 10 min or so over a meter. As neutron converter, 6Li and 235U are good for thermal neutrons and 232Th is useful for fast neutrons. When a neutron converter is not used, the method can be applied to the measurement of γ-ray intensity distribution.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A novel pulse-shape analysis method that uses similarity to recognize an individual pulse shape is presented in this paper. We obtain four pulse heights by using four linear amplifiers with different shaping time constants. We treat a combination of the four pulse heights as a pattern vector. A similarity of the pulse shape can be obtained by comparison between the pattern vector and a discriminant vector which was given in advance. Each pulse shape is analyzed by using the similarity. The method has been applied for the improvement of characteristics of a CdZnTe semiconductor detector. The characteristics of the energy spectrum of the CdZnTe detector such as the photopeak efficiency or the peak-to-valley ratio are improved after the correction procedure with the similarity.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese  

Language：English  

A new pulse shape recognition method with multi-shaping amplifiers, combined with a neural network algorithm, has been developed, where four pulse heights are sampled from one signal pulse through four linear amplifiers with different shaping time constants. The four pulse heights are used as characteristic parameters to recognize the pulse shape with a neural network. This method has been applied to signal processing for a CdZnTe semiconductor detector to improve the deteriorated energy spectra caused by pulse height deficits due to the different mobilities of electrons and holes in the detector. The neural network recognizes the pulse shape patterns and provides the corrective magnification factors of the pulse heights. After the corrective procedure, the energy spectrum for 137Cs gamma-rays is improved from 9.3 keV to 7.4 keV in the energy resolution (FWHM) of the 662 keV gamma ray photopeak. The photopeak becomes a considerably symmetrical shape without a low-energy tail. It has been verified that this method is simple and useful for pulse shape analyses, which can be used for many other applications.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

In the absolute radioactivity determination of gaseous samples using the internal gas counting method with proportional counters, evaluation of counting losses of pulses whose pulse heights are lower than the discrimination level is very important to obtain high accuracy. Counting losses due to wall effect and to very low energy of a β-ray were evaluated by experiment and EGS4 Monte Carlo calculation. The calculated results agreed well with experimental results when parameters in the EGS4 code were properly chosen; which shows the calculation code is able to be applied to other radioactive nuclides and other measurement conditions for the evaluation of counting losses.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A novel pulse-shape-analysis method that uses the similarity of patterns to recognize individual pulse shapes is presented. The principle of this method is described. The method has been applied to improve the gamma-ray energy spectrum of a CdZnTe semiconductor detector. The energy spectrum has been improved with increased photopeak efficiency and better energy resolution.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

To obtain a high precision in radiation or radioactivity measurements with an imaging plate, the photo-stimulated luminescence intensity must be large. To get the highest intensity, we reread an imaging plate repeatedly and summed each intensity for the purpose of reducing the variation of the measured intensities. A great improvement of the precision in the measurement was achieved with the method of repeated readings when the time interval between each reading is more than about 1 h.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Eigenvalue separation is an important index of power reactor stability in the view of neutronics. In recent years, a long, slender Position Sensitive Proportional Counter has been developed. By using this proportional counter, the spatial neutron flux distribution of a nuclear reactor can be measured rapidly. Using these characteristics, we intend to develop the experimental method evaluating eigenvalue separation as an index for reactor stability. A method based on spatial integrals of neutron flux measured at a subcritical system with an external source is proposed. To verify this method, experiments were carried out at Kyoto University Critical Assembly. It was confirmed that eigenvalue separation can be evaluated within a relative error of 10%.

Language：Japanese  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We have studied the improvement of gamma-ray energy spectrum characteristics of a CdZnTe semiconductor detector by means of a neural network algorithm. The neural network recognizes the pulse shapes and determines the corrective magnification factors of pulse heights. After the corrective procedure with the network, the gamma-ray energy spectra of some radioisotope sources become more ideal with better energy resolution.

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

A spherical neutron counter for spectroscopy and dosimetry has been developed. The counter consists of a spherical polyethylene moderator and three slender 3He position-sensitive proportional counters. Rough measurements of neutron fluence spectra and ambient dose equivalents, H*(10), have been done in the moderated-neutron field of JAERI. Characteristics of the counter are examined and compared with those of a Bonner sphere neutron spectrometer.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We present a new idea to apply a parallel plate collimator to an electronically collimated gamma camera, to reduce the complexity of image reconstruction. Back projected images obtained experimentally and using Monte Carlo simulations are shown. Using the collimator, backprojected images of single low-energy gamma-ray emitters can be obtained with larger signal-to-noise ratio than those obtained without the collimator. The results show that this method is useful in obtaining Tc-99m images.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

When the latent images formed by exposure with incident particles in the phosphor of Imaging Plate (IP) are irradiated with laser beam, photo-stimulated luminescence (PSL) is emitted and read through a photomultiplier. PSL intensity fades with increasing the elapsed time between the exposure and the PSL reading. When the IP is read successively, the PSL intensities decrease with the number of reading times. The tendency of the decreasing becomes gradual with increasing the elapsed time after exposure. The multiple successive reading method gives the means of the correction of the fading.

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A spherical neutron counter for spectrometry and dosimetry has been developed. The counter consists of a spherical polyethylene moderator and three slender 3He position-sensitive proportional counters inserted into the moderator. The thermal neutron distribution in the moderator, which is a function of the energy of the incident neutrons is obtained with the proportional counters. Characteristics of the counter have been studied with experiments and Monte Carlo simulations. Also shown are energy spectra of a 252Cf neutron source that are obtained by an unfolding method using the thermal neutron distributions as response functions.

Language：English  

A spherical neutron counter for spectroscopy and dosimetry has been developed. The counter consists of a spherical polyethylene moderator and three slender 3He position-sensitive proportional counters. Rough measurements of neutron fluence spectra and ambient dose equivalents, H*(10), has been done in the moderated-neutron field of JAERI. Characteristics of the counter are examined and compared with those of a Bonner sphere neutron spectrometer.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A single polarity charge sensing method has been studied using coplanar electrodes on 5 mm cubes of CdZnTe γ-ray detectors. This method can ameliorate the hole trapping problem of room-temperature semiconductor detectors. Our experimental results confirm that the energy resolution is dramatically improved compared with that obtained using the conventional readout method, but is still about an order of magnitude worse than the theoretical limit. A method to obtain the γ-ray interaction depth between the cathode and the anode is presented here. This technique could be used to correct for the electron trapping as a function of distance from the coplanar electrodes. Experimental results showed that a position resolution of about 0.9 mm FWHM at 122 keV can be obtained. These results will be of interest in the design of higher performance room-temperature semiconductor γ-ray detectors.

Language：English  

We present a new idea to apply a parallel plate collimator to an electronically-collimated gamma camera, to reduce the complexity of image reconstruction. Back projected images obtained experimentally and using Monte Carlo simulations are shown. Using the collimator, backprojected images of single low-energy gamma-ray emitters can be obtained with better spatial resolution and larger signal-to-noise ratio than those obtained without the collimator. The results show that this method is useful in obtaining Tc-99m images.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Distribution images of natural radioactivity contained in various natural materials such as vegetable, animal meat and pottery work can be obtained with an imaging plate which has high sensitivity for nuclear radiations. For such very low levels of radioactivity, natural background radiations must be reduced using a shielding box. The lining, on the inside of the box, with low atomic number material such as acrylic resin is very effective in reducing electrons, β-rays and low energy X- and γ-rays emitted from the inner surface of the shielding material. Some images of natural radioactivity distribution were obtained and the radioactivity, mainly 40K, contained in natural materials was measured by using an HPGe detector and also the imaging plate itself.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

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

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We have developed a unique neutron counter applicable to measurements of fluence, energy distribution and the dose equivalent of neutrons with very wide energy range, and to estimations of incident direction of neutron beams. This 4π sensitive neutron counter consists of a spherical polyethylene moderator and three charge-division-type position-sensitive proportional counters (PSPCs) inserted into the moderator orthogonally with each other. The three PSPCs give thermal neutron distributions in the spherical moderator that bring us the above information. The characteristics of this neutron counter have been studied with Monte Carlo simulations and with experiments using monoenergetic neutrons.

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A long and slender position-sensitive 3He proportional counter with an outer diameter of 8mm and an effective length of 1.2m has been developed to measure neutron flux distributions in a critical assembly. Because it is difficult to make such a long and slender counter of con- ventional structure where an anode wire is stretched at the center of a cylindrical cathode tube, three prototype electrode systems of which anode wires are supported by insulator plates have been proposed. Among these three electrode systems, the electrode system of which anode wire is stuck on a ladder-shaped insulator has been adopted. The neutron flux distributions in the core of the Kyoto University Critical Assembly (KUCA) have been measured with the counter. Some non-uniformity of the detection efficiency has been observed throughout the counter. This non-uniformity has been corrected by calibrating the position-dependent detection efficiency with a gold wire activation method. A fairly satisfactory distribution, where the relative deviation from the gold wire activation method is 5.0%, has been obtained. Though the non-uniformity of the detection efficiency should be solved for precise measurements, the counter can be used for quick and rough measurements of neutron flux distributions.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

In a charge-division type position-sensitive proportional counter (PSPC) with an anode wire of small resistance, a reflected component from an opposite end and thermal noise involved in signals deteriorate the position resolution of the PSPC. A digital waveform processing method was applied to the reduction of these undesirable effects by skillfully utilizing their signal characteristics that can be observed as inversely correlative signals between two-output signals from both sides of the PSPC. The digital waveform processing could improve the position resolution compared to a conventional pulse height processing method with analog filters. When the digital waveform processing was applied to signals of an equivalent circuit simulating the PSPC, the position resolutions defined by the full width at half maximum were improved to about 30% of those of conventional analog pulse processing. In the case of an actual PSPC, the position resolutions by the digital waveform processing were improved by 4-10% as compared with those of conventional pulse height processing.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

This paper describes a new method of microphonic noise reduction by digital waveform processing. This method predicts the microphonic noise shape over the duration of a detector signal by making full use of the periodicity of the noise, and then removes the microphonic noise component from the detector signal. Preliminary experimental results that prove the validity of this method are presented.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

In the absolute radioactivity measurement of radioisotope gaseous samples with newly developed position-sensitive proportional counter (PSPC) method, it is necessary to change the counting gas pressure for the correction of the wall effect. The position signal was found to drift depending on the pressure. Theoretical explanation was given for this drift. Rise time of output pulses varies with gas pressure, which leads to a change of ballistic deficit. Consequently, the ballistic deficit differs between pulses from both the ends of the PSPC, which causes the change of position signals. Increasing the pressure of the counting gas from 0.5×105Pa to 4×105Pa, the range of position signals for two position calibration sources became narrower by about 8% under 6μs shaping time.

Language：English  

This paper describes a new reduction method of microphonic noises, or some other periodic noises by means of digital waveform processing. This method predicts the microphonic noise shape over the duration of a detector signal by making full use of periodicity of the noise, and then removes the noise component from the detector signal. Experimental results that prove the validity of this method are presented.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The influences of wall effects and saturation of the gas multiplication on position resolutions of position-sensitive 3He proportional counters have been studied by means of numerical calculations, computer simulations and experiments. When the proton produced by the 3He(n,p)t reaction loses its specific energy in a counter wall by wall effects, a good position resolution is obtained escaping from any effects of a finite range of the proton and the triton. In the case where the gas multiplication is saturated, the best position resolution is obtained by selecting low pulse height events that the protons and the tritons move perpendicularly to the anode wire.

Language：English  

We have developed a unique neutron counter applicable to measurements of fluence, energy distribution and the dose equivalent of neutrons with a very wide energy range, and to estimations of the incident direction of neutron beams. This 4π sensitive neutron counter consists of a spherical polyethylene moderator and three charge-division-type position-sensitive proportional counters (PSPCs) inserted into the moderator orthogonally with each other. The three PSPCs give thermal neutron distributions in the spherical moderator that bring us the above information. The characteristics of this neutron counter have been studied with Monte Carlo simulations and with experiments using monoenergetic neutrons.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The self-attenuation of photons was analytically calculated for an 192Ir metallic wire source and an aqueous standard source. The influence of the self-attenuation on the current of the calibrated ionization chamber was also evaluated. The self-attenuation did considerably affect the ionization current. It was concluded that the apparent radioactivity must be multiplied by a correction factor larger than unity (1.09±0.01 in the present case) to get the true radioactivity when the radioactivity of the 192Ir metallic wire source was measured with the ionization chamber calibrated with the aqueous standard source of 192Ir.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Radioactivities of metallic 192Ir sources are measured with a microcalorimeter nondestructively. In order to convert the complete decay energy evolved from the source into thermal energy, a tungsten block is used as radiation absorber. The sample sources measured are four thin wires of Ir/Pt alloy with dimensions of 0.1 mmø × 10 mm1, each coated by 0.1 mm thick platinum, giving the final diameter of 0.3 mmø. Overall uncertainty of the measurement for some 60 MBq activity is ±3.2%. Measurements of the wire sources with an ionisation chamber give smaller activities which are smaller by 10% than those from microcalorimetry mainly because of the autoattenuation effect.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Direct measurement of gaseous activities by the diffusion-in long proportional counter method (DLPC method) was studied. The measuring time without end effect was estimated by observing the behavior of 37Ar in the counter and was long enough to carry out the accurate activity measurement. The correction for wall effect was also examined on the basis of the measured and calculated correction factors. Among the tested gases of methane, P10 gas and propane, P10 gas was made clear to be a suitable counting gas for the DLPC method because of good diffusion properties and small wall effect. This method is quite effective for standardization of gaseous activities used for tracer experiments and calibration works of radioactive gas monitoring instruments.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Direct radioactivity measurement of 85Kr is difficult with ionization chambers, since it emits high-energy β-rays (Eβmax = 667 keV) which results in a severe wall effect. Also with proportional counters, the end-effect must be taken into account. The position-sensitive proportional counter (PSPC) method which can eliminate the end-effect was applied to direct measurement of 85Kr radioactivity. In the measurement, logarithmic amplifiers were employed to clearly distinguish between β-ray signals and noise signals, and to eliminate digital error in the calculation of position information. The radioactivity of 85Kr was determined with ±0.80% standard deviation.

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We have developed a novel position-sensing method of a proportional counter using slow and fast components in the output signal observed at one end of a resistive anode wire of which the other end is grounded through a capacitor. This paper describes the principle of the position sensing and some experimental results. Fairly sufficient characteristics in position resolution and integral linearity were obtained. This method will extend the application field of position-sensitive detectors.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Fulfillment of both observation of pulses ranging from about 10 mV to 10 V through ADC and carrying out an arithmetic calculation with small digital errors for such digitized pulses is usually difficult, although it is required in measurements using a charge-division-type position-sensitive proportional counter (PSPC). However, the use of a logarithmic pulse amplifier sometimes solves this problem. The advantage of using a logarithmic pulse amplifier is described through the application of the amplifier to absolute-radioactivity measurements of gaseous samples and to the simultaneous measurement of geometrical distributions of neutrons and gamma-rays with the PSPC.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We propose a novel position-sensing method using slow and fast components in an output signal observed at one end of a resistive anode wire in a proportional counter in which the other end of the anode wire was grounded through a capacitor. Fairly sufficient characteristics in position resolution and an integral linearity were obtained. This method will extend the application field of a position-sensitive detector.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A position sensitive 3He proportional counter for thermal neutrons with a novel signal readout method which has two pre-amplifiers at only one end of the counter body has been developed. It has an advantage for usage in a special environment, such as in a subcritical facility or in water, or for insertion into a narrow space. The characteristics of the counter were evaluated with thermal neutrons. The position resolution was 7 mm with an effective length of 1, 200 mm. The integral non-linearity of position signal was less than 0.5%.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

It is generally difficult to insert a position sensitive proportional counter (PSPC) with a conventional charge division in a narrow space, or to work the counter under special environments, such as in water or in a reactor. We improved the position signal readout to make it possible to use a PSPC under such environments. A position signal was extracted from only one end of an anode wire by grounding the other end through a capacitor and a total charge signal was obtained from twelve cathode wires stretched parallel to the anode wire, so that two pre-amplifiers were able to be connected at only one end of the counter. The character-istics of the PSPC with the improved signal readout were examined with X-rays. The position resolution was 1.3 mm with an effective length of 550 mm, and depended on the X-ray injection position. A non-linearity of position signals was less than 0.2%.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A multielement position sensitive proportional counter was developed for the measurement of 3H labeled gas movement in a pipe by internal counting. The counter consists of an outer cylindrical pipe with an inner diameter of 40 mm, seven resistive stainless steel anode wires with a diameter of 22μm, and 24 cathode wires with a diameter of 120μm. These wires divide the radial cross section of the pipe into seven regions. Since each region independently works as a position sensitive proportional counter and the seven resistive anode wires are connected in series through lump resistors, the region and the axial position where a β-decay event occurred can be known by a simple operation upon the charge signals obtained from two preamplifiers. The axial position resolution for 3H β-rays was 9 mm FWHM. Demonstrative experiments were performed for the flow and diffusion of 3H labeled ethane in the counter pipe.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

It is well known that adsorption of electronegative or electropositive atoms on a metal surface results in charge transfer between the metal conduction band and the adsorbate atom. This charge transfer results in the formation of a coverage-dependent image dipole and a consequent change in the work function and adsorbate binding energy. Additionally, the secondary electron yield and the charge state of surface atoms desorbed by thermal, electron impact or ion impact desorption processes are closely related to the effective adsorbate charge.

We discuss here the effect of Gibbsian segregation as a means of producing similar effects for electropositive (alkali metal) layers on a number of metal substrates. Classical chemisorption theory is used as a means of estimating the adsorbate effective charge and the results are compared with models used to predict the secondary ion fraction of sputtered atoms. The resulting concept of self-sustaining sputter-resistant coatings is analyzed in the context of applications to the fusion environment as well as to, e.g., materials for high current electrical contacts.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A new partial pressure gauge is proposed that is capable of measuring partial pressures of He and D2 gases in the mixture. The gauge consists of a conventional ion scattering spectrometer with a Wien filter. The influence of the residual gases CH4 and H2O on the pressure measurements of D2 and He in this gauge is discussed.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

In parallel to the conceptual design of the R-tokamak, research and development efforts on
the systems and the components have been carried out to obtain scopes to realize the device.
Because we intended to introduce DT fuels into the device, the items of research and
development works are quite different to that of non-burning machines. Alminium alloy
developments to avoid activations by 14 MeV neutron irradiations, tritium safe handling and
vacuum system with tritium are examples of this category. Beside specific requirement directly
caused by DT introduction, highly reliable operation of the machine is strongly requested,
because it is the necessary condition to perform experiments safely. However, these efforts are
still in an early stage of investigation and many efforts are needed to prepare a rigid data base
tokamak operation with reacting plasma.

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A position sensitive proportional counter of a charge division type with a single resistive anode wire was constructed for the measurement of the movement of 3H labelled gas which is flowing or diffusing in a pipe. The introduction of resistors between the anode wire and pre-amplifiers brought a uniform detection efficiency for 3Hβ-rays throughout the counter. The position resolution was 3.1 mm FWHM. Detection efficiency was almost 100% uniformly over about 700 mm in the total anode length of 740 mm. The movement of 3H labelled gas could be measured effectively.

Language：English

Language：Japanese

Language：English

Language：English

Event date： 2023.11

Language：Japanese   Presentation type：Poster presentation  

Venue：静岡県コンベンションアーツセンター  

Event date： 2023.11

Language：Japanese   Presentation type：Poster presentation  

Venue：グランドニッコー東京台場ホテル  

Event date： 2023.11

Language：Japanese   Presentation type：Poster presentation  

Venue：グランドニッコー東京台場ホテル  

Event date： 2023.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2023.9

Language：Japanese   Presentation type：Poster presentation  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

Event date： 2022.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

Event date： 2022.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.10

Language：Japanese   Presentation type：Poster presentation  

Venue：つくば市  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2022.3

Language：Japanese   Presentation type：Poster presentation  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.12

Language：English   Presentation type：Oral presentation (general)  

Event date： 2021.12

Language：English   Presentation type：Oral presentation (general)  

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.10

Language：English   Presentation type：Poster presentation  

Venue：WEB  

Event date： 2021.10

Language：English   Presentation type：Poster presentation  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.11 - 2020.12

Language：English   Presentation type：Oral presentation (general)  

Venue：WEB   Country：Japan  

Event date： 2020.11

Language：Japanese   Presentation type：Poster presentation  

Country：Japan  

Event date： 2020.11

Language：English  

Venue：online  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Symposium, workshop panel (nominated)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：ＷＥＢ   Country：Japan  

Event date： 2020.8

Language：Japanese  

Event date： 2020.7

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

福島第一原子力発電所（1F）の廃炉作業を円滑に進めるためには、線量率及び放射性物質の分布を詳細に把握する必要がある。これまでに登壇者らは光ファイバーを用いた新しい一次元放射線分布測定法として、ファイバー内での光の減衰量が波長依存であることを利用し、ファイバー片側から波長スペクトルを測定し発光位置分布を逆推定する「波長分解分析法」を提案し、基本的な線源位置分布測定が可能であることを確認した。本発表では波長分解分析法の位置決定精度やファイバーの耐放射線性に基づく適用範囲等について検証した結果を報告する。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

核融合炉ブランケットは、中性子の減速・遮蔽、トリチウムの増殖、熱の取り出しといった役割を有する。ダイヤモンド検出器はブランケットにおける高速中性子束やトリチウム発生量の実時間測定のための有用なモニタとして期待されるが、ガンマ線に感度を有するため、ガンマ線の寄与を適切に除す必要がある。
本研究では単結晶CVDダイヤモンド検出器をリチウム材料と組み合わせ、中性子照射環境下で発生する高エネルギートリトンの直接測定を実施した。波形弁別と粒子輸送計算によりトリチウム発生量の定量手法について評価した。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

ホウ素中性子捕捉療法において、ホウ素と中性子の反応率（すなわち治療効果）を定量的に評価することが求められている。本研究グループでは、単結晶CVDダイヤモンド検出器とホウ素化合物とを組み合わせ、中性子照射下でホウ素中性子捕捉反応により発生する高エネルギー荷電粒子を直接測定する方法について評価を行っている。本発表では、中性子照射環境下でホウ素化合物から発生するアルファ線の直接測定およびアルファ線とガンマ線の波形弁別結果について報告する。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

老朽化する大型インフラの長期保守管理をより効率的に行うために非破壊で内部情報を取得できる技術の開発が期待されている。X線を用いた非破壊検査の手法の中に後方散乱X線撮像法があり、この手法では被写体の片側にX線源と検出器を設置して検査を行うことができる。本研究においてはコリメータ等の重量物を稼働させることなく一次元プロファイルが取得可能なファンビームX線方式を採用している。この検査手法の課題として検査スピードの向上が挙げられている。そこでシンチレータをCWOからCsI:Tl結晶に変更、集光体系をCMOSカメラからフォトダイオードアレイに変更した検出器を製作し、性能を評価した。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

炭素線治療はスキャニング照射法などの技術を用いて腫瘍のみを選択的に損傷させることが可能である。安全に治療を行うためには体内での線量評が求められている。そこで我々は光ファイバーの先端に光刺激蛍光体を配した小型線量計の開発を行っている。今回は、小型線量計の治療場での応用に向けて炭素線照射実験を行った。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

BNCT照射場のような中性子が支配的で、実測困難なエネルギースペクトル場の人体に対するガンマ線量を正確に把握するために、我々は組成が人体に近く中性子感度が低いとされるBeOに注目し、OSL線量計として利用するための測定体系や測定方法を検討した。また、中性子とガンマ線が混在する場でガンマ線線量の実測を行った。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福島大学   Country：Japan  

小型加速器中性子源での利用を想定した高効率な中性子回折計の開発を進めた。粉末中性子回折を想定し、柔軟性の高いTRUST Eu：LiCAFシンチレータを用いた円環状中性子検出器を多数配置し、大立体角を有する中性子回折計を製作し、京都大学加速器中性子源KUANSにて基礎試験を実施した。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学四谷キャンパス   Country：Japan  

TlBr検出器の開発の効率を図るためには、個々の製作プロセス間で、結晶の品質を評価可能な手法の開発が望まれている。本研究では、その試みの一つとして、中性子ブラッグディップ法を用いた評価手法を提案し、その特性について調べることを目的としている。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学四谷キャンパス   Country：Japan  

炭素線治療のスキャニング照射法は腫瘍にのみ集中的に線量付与することが可能である。安全に治療を行うためには体内での線量評が求められている。そこで我々は光ファイバーの先端に光刺激蛍光体を配した小型線量計の開発を行っている。今回は、小型線量計を用いてスキャニング法による炭素線治療場への応用を検討した。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学四谷キャンパス   Country：Japan  

ダイヤモンド検出器の表面にリチウムやホウ素を含む化合物を付与することにより、(n,a)反応により発生するアルファ線や高エネルギー荷電粒子を直接測定することが可能である。本研究では、パルス波形弁別に基づくコードを確立し、リチウムやホウ素化合物を付したダイヤモンド検出器への中性子照射実験を行い、荷電粒子の定量評価を行う。

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：上智大学四谷キャンパス   Country：Japan  

我々の研究グループでは、高強度中性子場において使用可能なリアルタイム中性子モニタとして、光ファイバ型中性子検出器の開発を行っている。本研究では、中性子検出媒体にLiガラスを用いて検出器を製作、その計数率特性を評価し、従来の約10倍の計数率においても出力線形性を維持できることを示した。さらに、放射線耐性の評価では、熱中性子フルエンス2×10¹² n/cm²を超える中性子照射において、検出器の劣化は確認されなかった。

Event date： 2020.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学青葉山新キャンパス   Country：Japan  

Event date： 2019.11

Language：English   Presentation type：Poster presentation  

Venue：Howard Beach Resort Kenting, Kaohsiung, Taiwan   Country：Taiwan, Province of China  

Neutron diffraction is one of the structural analysis methods of materials. Unlike X-ray diffraction, neutron diffraction has the feature that neutrons can penetrate to the deep part of some materials, and analysis of light elements is possible. However, at present, facilities that can conduct neutron utilization research including neutron diffraction are limited to large facilities. In order to overcome such a situation, many compact accelerator neutron source (CANS) facilities are under development. It is important to effectively use neutrons in CANS because neutron intensity is low compared to large facilities. Therefore, it is desirable for neutron diffractometers to have large a solid angle. In general, neutron diffractometers that cover large solid angles are large and very expensive equipment. In this study, we aim to realize a compact and large solid angle neutron diffractometer. Our research group has been developing the Transparent rubber sheet type Eu:LiCaAlF6 (TRUST Eu:LiCAF scintillators), which are highly flexible neutron scintillators. It has become possible to make the circular neutron detectors by using the TRUST Eu:LiCAF scintillators and a wavelength-shifting fiber light readout system. A neutron diffractometer with a multiple ring structure consisting of many neutron detectors as shown in Fig. 1 was fabricated.
Neutron diffraction experiments were carried out using one of such compact neutron sources in Kyoto University (KUANS). Although KUANS has low neutron flux, diffraction peak of silicon powder is clearly observed as shown in Fig. 2. This is because the diffractometer covers a large solid angle, and it has been demonstrated that a diffraction peak of a material having a low diffraction intensity such as silicon can be obtained at KUANS. In addition, iron powder diffraction pattern was measured. The minimum resolution of the 110 reflection is 3.0%. This resolution can be expected for engineering applications such as residual austenite measurement.

Event date： 2019.10 - 2019.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Manchester   Country：United Kingdom  

Event date： 2019.10 - 2019.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Manchester   Country：United Kingdom  

Event date： 2019.10 - 2019.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Manchester   Country：United Kingdom  

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：北海道大学札幌キャンパス   Country：Japan  

シンチレータ粉末とコンバータ粉末を混ぜ合わせる混合粉末シンチレータは、任意の組成を実現でき、シンチレータ選択の自由度を高めることが可能である。本研究では、コンバータとしてLiFを採用し、これと様々な蛍光体粉末を組み合わせて混合粉末シンチレータを製作し、既存の透明結晶シンチレータとの比較を通じて応答評価を行うことで、既存のシンチレータを凌駕する新規中性子検出媒体の開発に向けた基礎研究を行った。

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：北海道大学札幌キャンパス   Country：Japan  

粒子線の高線エネルギー付与（LET）領域では光刺激蛍光体は消光現象により感度が低下する。消光現象による感度低下は蛍光体内部のエネルギー付与密度に関係することが考えられる。今回は光刺激蛍光体の感度変化を比エネルギー計算により評価し実験により得られた結果と比較検討を行った。

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学札幌キャンパス   Country：Japan  

本研究は、TlBr検出器を大型化することで、高エネルギー分解能かつ高感度なTlBr検出器を開発することを目的としている。そのためには電極構造や信号読み出しの工夫が必要不可欠である。そこで、信号読み出し数が少なく、他の化合物半導体検出器でも実績のあるコプレナーグリッド型電極に着目し、TlBr検出器への適用を検討した。

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北海道大学札幌キャンパス   Country：Japan  

社会インフラ設備の長期保守管理をより効率的に行うことができる非破壊検査手法の一つに後方散乱X線検査がある。この手法では被写体の片側にX線源と検出器を設置して検査が可能である。本研究ではコリメータ等の重量物を稼働させずに1次元プロファイルを取得できるファンビームX線方式を採用し、ファンビームX線に直行する平行平板コリメータで散乱位置を限定している。先行研究で製作された検出器の要素検討を行いシンチレータと発光取得体系の変更した新たな検出器を製作した。

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：北海道大学札幌キャンパス   Country：Japan  

臭化タリウム（TlBr）は室温動作可能な化合物半導体検出器として期待されている。TlBr結晶の品質評価に、中性子ブラッグディップイメージングを適用した。ディップ波長の位置依存性が確認された。

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：北海道大学札幌キャンパス   Country：Japan  

BNCT照射場のような中性子が支配的で、実測困難なエネルギースペクトル場のガンマ線量を正確に把握するには、これら素子の中性子に対する感度評価や線量計応答のエネルギー依存性に関する詳細検討が必要である。そこで本研究では、中性子感度が低いと考えられているBeO熱刺激蛍光体(TLD)と、読出しが簡便で比較的安定性の高いC:Al2O3光刺激蛍光体(OSL)のBNCTへの適用性の検討を進めた。

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

福島第一原子力発電所（1F）の廃炉過程における作業者の被ばく線量低減及び効率的な除染計画立案を行うためには、局所的に存在するホットスポットの分布を把握する必要がある。シンチレーション光ファイバーに飛行時間法を適用した広域一次元放射線分布測定システムが1F事故後に広く応用されてきたが、1F原子炉建屋内のような高線量率の環境では回路系のパイルアップやセンサーの偶発同時計数が問題となる。そこで、パイルアップ等の問題を回避できる積分型の測定手法として、光ファイバーの片側から波長スペクトルを読み出し、ファイバー内での光の減衰が波長依存であることを利用して放射線入射位置を特定する「波長分解法」の原理検証試験を実施した。

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山大学五福キャンパス   Country：Japan  

ホウ素中性子捕捉療法に用いる中性子場の構築、人体内での中性子の減速過程の評価、治療効果のモニタリングのため、ホウ素中性子捕捉反応の実時間・定量測定が求められる。本研究では単結晶CVDダイヤモンド検出器をホウ素材料と組み合わせ、中性子照射下でホウ素中性子捕捉反応により発生する高エネルギーイオンを直接測定することで、ホウ素中性子捕捉反応発生率の定量評価手法を確立する。

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学キャンパス宇治おうばくプラザ   Country：Japan  

本研究では、生物・物理・医学・工学分野の研究者が連携することで、
ホウ素中性子捕捉反応に伴う荷電粒子の発生を制御・計測し、DNAの
二重鎖切断や細胞内DNA修復速度からBNCTの治療効果を定量する。

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：京都大学キャンパス宇治おうばくプラザ   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：京都大学キャンパス宇治おうばくプラザ   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：京都大学キャンパス宇治おうばくプラザ   Country：Japan  

Event date： 2019.9

Language：Japanese   Presentation type：Poster presentation  

Venue：京都大学キャンパス宇治おうばくプラザ   Country：Japan  

名古屋大学では、2015年にダイナミトロン加速器を設置して以降、加速器の調整、中性子の発生、中性子場の特性評価を行ってきた。2016年度から2018年度にかけては、国立研究開発法人日本医療研究開発機構殿より岡山大学と共同で医療機器開発推進研究事業の委託を受け、１）中性子生成減速装置(BSA)の開発、　２）中性子照射場の特性評価、 ３）BNCT線量評価、 ４）加速器型BNCTガイドライン策定に向けた取組み、 ５）非臨床試験（細胞実験）　を行ってきた。本大会においては、中性子照射場の特性評価結果、中性子発生に用いるリチウムターゲットの開発状況、細胞実験結果について発表する。

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都大学キャンパス宇治おうばくプラザ   Country：Japan  

Event date： 2019.5

Language：English   Presentation type：Oral presentation (general)  

Country：Portugal  

The single crystal CVD diamond detector (SDD) was installed in the torus hall
of the Large Helical Device (LHD) to measure neutrons with high time resolution and neutron
energy resolution. The LiF foil with 95.62 % of 6Li isotope enrichment pasted on the detector was
used as the thermal neutron convertor as the energetic ions of 2.0 MeV alpha and 2.7 MeV triton
particles generated in LiF foil and deposited the energy into SDD.
SDD were exposed to the neutron field in the torus hall of the LHD during the 2nd campaign
of the deuterium experiment. The total pulse height in SDD was linearly propotional to the
neutron yield in a plasma operation in LHD over 4 orders of magnitude. The energetic alpha and
triton were separately measured by SDD with LiF with the thickness of 1.9 μm, although SDD
with LiF with the thickness of 350 μm showed a broadened peak due to the large energy loss of
energetic particles generated in the bulk of LiF. The modeling with MCNP and PHITS codes well
interpreted the pulse height spectra for SDD with LiF with different thicknesses. The results above
demonstrated the sufficient time resolution and energy discrimination of SDD used in this work.

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学　農学部　弥生講堂・一条ホール   Country：Japan  

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

中性子ブラッグエッジ解析コードRITSは非線形最小二乗フィッティングを行うものであるが、その収束値の不安定性を解消するための検討を行った結果を報告する。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

名古屋大学で開発中の加速器BNCT用システムの整備進捗状況について発表する。ダイナミトロン型加速器を用いており、加速電圧は2.8MeV、最大電流は15mAである。本システムならびに各コンポーネントの概要と、特長、発生中性子の特性等について紹介する。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

大型ヘリカル装置で実施された重水素プラズマ実験2ndキャンペーンにおいて放射化法を用いて構造材料の放射化物形成量を測定し、将来的な廃止措置に関わる放射化物の予測を行った。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

本研究では、名古屋大学で開発中のBNCT用加速器型中性子源のLi封入型ターゲットの健全性について評価した。陽子エネルギー2.8MeV、電流1.5mAの陽子ビームを照射した結果、 Ti 箔は健全性を保ち、熱除去性能を達成したことを実験的に確認できた。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

名古屋大学ではBNCT用加速器型中性子源を開発している。本装置では、中性子生成のために15mAの大電流静電加速器を用いる。ターゲットに適切にビームを照射するため、加速器からの陽子ビームの情報を得ることが重要である。本研究では、回転式プロファイルモニターを製作し、陽子ビームプロファイルおよびビーム位置の測定及び電流値が測定できることを実験的に確認した。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

粒子線治療などの放射線治療は精細な線量分布を形成することが可能である。安全に治療を行うために体内の実際に体内で線量測定を行うことが求められている。そこで我々は光ファイバーの先端に放射線誘起蛍光体を配した線量計の開発を行っている。今回は、線量計の実用化に向けて実際の治療場での応答評価試験など線量計の特性評価を行った。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

高エネルギー分解能を示す臭化タリウム半導体検出器の検出効率向上を目指し、検出器の大型化の際に問題となる事項に関する検討を行った。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：茨城大学水戸キャンパス   Country：Japan  

シンチレーション光ファイバーセンサーに飛行時間法（Time-of-Flight法、TOF法）を適用した高線量率用TOF光ファイバー放射線センサーを開発した。ガンマ線照射場において照射試験を実施し、高線量率環境下での動作特性を評価した。

Event date： 2019.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：北海道科学大学   Country：Japan  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京工業大学大岡山キャンパス   Country：Japan  

中性子ブラッグエッジ解析コードRITSのシングルエッジ解析モードの不安定性を改善すべく、コードの改良を行った結果を報告する。

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京工業大学大岡山キャンパス   Country：Japan  

粒子線治療などの放射線治療は精細な線量分布を形成することが可能である。安全に治療を行うために体内の実際に体内で線量測定を行うことが求められている。そこで我々は光ファイバーの先端に放射線誘起蛍光体を配した線量計の開発を行っている。今回は、線量計の実用化に向けて実際の治療場での応答評価試験など線量計の特性調査を行った。

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京工業大学大岡山キャンパス   Country：Japan  

Event date： 2019.3

Language：English   Presentation type：Oral presentation (general)  

Venue：東京工業大学大岡山キャンパス   Country：Japan  

中性子回折は物質の構造解析手法の一つであり、X線回折と相補的な関係にある。一般に大立体角中性子回折装置は大型になるが、本研究では柔軟な中性子シンチレータのTRUST Eu:LiCAFを用いることにより小型かつ大立体角の中性子回折装置を製作した。製作した中性子回折装置が中性子強度の高くない京都大学の小型加速器中性子源（KUANS）にて回折中性子を検知することができるか応答評価試験を行った。

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東桜会館   Country：Japan  

名古屋大学は、Li ターゲットを用いたBNCT 用加速器中性子源の開発を行っている。Li ターゲットに
入射する陽子ビームは、IBA 社製のダイナミトロン加速器で生成され、最大エネルギー2.8 MeV、電流15
mA（42 kW）である。数MeV の低い陽子エネルギーでは、Li (p,n)Be 反応による中性子発生強度がBe(p,n)B
反応と比較して髙いため、Li はBNCT 用のターゲットとして適している。しかしながら、金属Li の融点が180 度と低いことから、大電流の陽子を照射すると大量の熱が付与されLi が溶融してしまう問題がある。これらの問題を解決するため、冷却機能付きLi 封入型ターゲットを考案し、その開発を進めている。これまでに、乱流を促進する構造をもつ冷却チャンネルにより、冷却基板に照射される高熱流束（＞15 MW/m2）を十分に除熱出来ることが電子ビームを用いた実験において確認した。本研究では、小型Li ターゲットを作製し、Li ターゲットの熱除去性能とTi 箔の健全性を陽子ビーム照射によって評価する。

Event date： 2018.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東桜会館   Country：Japan  

がんの新たな治療法の1 つとして現在、ホウ素中性子捕捉療法(BNCT)の研究が進められている。BNCT では患者に腫瘍細胞に集積する性質を持つホウ素化合物を体内に投与し、その後、体外から
中性子照射を行うことで¹⁰B(n,α)⁷Li 反応を誘起して、放出されるα線と⁷Li 粒子によって腫瘍細胞を選択的に攻撃する治療法である。このBNCT で患者に与えられる線量は、¹⁰B(n,α)⁷Li 反応起因のホウ素線量、高速中性子起因の水素線量、¹⁴N(n,p)¹⁴C 反応起因の窒素線量とガンマ線量に分けて評価される。本研究では、この中のガンマ線量の評価法に関する検討を行っている。ガンマ線量の最も基本的な評価手法は電離箱を用いたものであるが、複雑な形状のファントム内での線量分布評価や、ホウ素薬剤の性能評価に用いられる細胞実験のように、電離箱を設置するのが困難な照射場におけるガンマ線量評価には、小型で電源不要な熱刺激蛍光体（TLD）や光刺激蛍光体（OSL）といった個人線量計素子の利用が望ましい。しかし、BNCT 照射場のような中性子が支配的な場でガンマ線量を正確に把握するには、これら素子の中性子に対する感度評価や線量計応答のエネルギー依存性に関する検討が必要である。そこで、中性子感度が低いと考えられているBeO 熱刺激蛍光体と、読出しが簡便で比較的安定性の高いC:Al₂O₃ 光刺激蛍光体のBNCT への適用性の検討を進めた。

Event date： 2018.11

Language：English   Presentation type：Poster presentation  

Venue：Toki Japan   Country：Japan  

Event date： 2018.11

Language：English   Presentation type：Poster presentation  

Venue：International Convention Centre Sydney, in Sydney,   Country：Japan  

We are developing a new type of neutron scintillator. This type of scintillator consists of mixed powder of a neutron converter and a scintillator, like a famous LiF-Ag:ZnS neutron scintillator. The LiF-Ag:ZnS mixed powder is a very bright scintillator. However, the detection efficiency and effective thickness of this type of a neutron scintillator is limited because it is opaque due to quite high refractive index of the Ag:ZnS. Large gaps in the refractive index at interfaces of particles induce refractions with large angles. Therefore, scintillation photons must run for quite long path before escaping from a scintillator region. If mixed powder scintillator can be roughly transparent, we can freely change the scintillator composition, especially for lithium content and easily increase the scintillator thickness. Transparency of a mixed powder scintillator can be improved by choosing a converter and a scintillator with similar refractive indices and filling a refractive index buffer, such as liquid glass resin. We can choose a scintillator material with various properties, such as fast decay, high light yield etc. In this paper, we attempt to use LiF and Eu:CaF2 mixed powder to demonstrate a roughly transparent mixed powder neutron scintillator. The fabricated mixed powder scintillator was roughly transparent. We evaluated the scintillator responses for neutrons and gamma-rays. The scintillator showed a peak shape in a pulse height spectrum when irradiated with thermal neutrons.

Event date： 2018.11

Language：English   Presentation type：Poster presentation  

Venue：International Convention Centre Sydney, in Sydney,   Country：Japan  

We are developing optical fiber type neutron detectors using a small piece of transparent Li-based scintillator as a real-time neutron monitor. This type of neutron detector consists of a small transparent scintillator, an optical fiber light guide and a photodetector, such as a photomultiplier tube. A wide dynamic range or wide linearity of signal output is one of the important specifications for neutron monitors. Especially, the counting rate often saturates in a high flux field. In high counting rate situation, this saturation behavior is caused by signal pulse pile-up. The pulse pile-up induces distortion of signal pulse shapes and counting losses. In our system, photomultiplier tube signals were integrated with a RC integrator and then processed with digital multi-channel analyzer (MCA) to extract pulse heights, detection timing and signal rise time. Signals through the RC integrator have an exponential decay component. In pulse pile-up events, signal pulse shapes were distorted by this decay component. The signal pulse heights were reduced in the pile-up events and depended on the counting rate. We implemented the pulse height correction function using information of detection time from a previous event and a previous pulse height in the signal processing procedures. This correction function successfully reduced distortion in pulse heights. In addition, we implemented the counting loss correction function. The corrected count rate shows no saturation behavior in a high count rate region over 100 kcps. The linearity of signal output was improved by the pulse height correction and the counting loss correction.

Event date： 2018.11

Language：English   Presentation type：Poster presentation  

Venue：International Convention Centre Sydney, in Sydney,   Country：Japan  

Radiotherapies are one of the main treatment modalities in cancer management. In order to accurately estimate the irradiation dose, it is better to insert a dosimeter into an affected region in a patient body. We, therefore, are developing a small size dosimeter consisting of an optical fiber and optically stimulated luminescence (OSL) elements. The OSL elements shows the quenching effect when high linear energy transfer (LET) particles are irradiated. In order to correct the quenching effect, using signal ratio from different OSL materials is considered to be effective. Since the effective correction could be achieved by using proper combination of OSL materials, various dosimeter materials are required to realize the suitable combination of OSL materials for the quenching effect correction. Investigation of the mechanism of the OSL process will help to look for new OSL elements. In this paper, we investigate the dependency on some parameters of exponential decay coefficients of the OSL signals in order to understand the OSL mechanism. We prepared the CaF2 OSL elements with different Ce dopant concentrations of 0.1, 0.5 and 1.0%. The OSL signals often have two decay components. The both decay coefficients linearly depend on the stimulation laser intensity. We compared the slopes of the decay coefficients in the OSL signals to the laser intensity for various Ce dopant concentrations. We confirmed that the slopes of the decay coefficients depend on the Ce concentration and decrease with the Ce concentration. These knowledge are expected to help to understand the OSL mechanism.

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Poster presentation  

Venue：Taipei, Taiwan   Country：Japan  

We designed the moderator with a Monte-Carlo simulation code of PHITS based on a nuclear data JENDL-4.0.
The source particles of the simulation are neutrons whose energy and momentum distributions are generated from a calculation code based on experimental data. The neutron yield from the target is 1.4 × 109 n/μC. The proton beam current was assumed to be 600μA. In order to maximize the produced thermal neutron flux, we planned to fill a collimator for fast neutron extraction hole with moderator material. We compared the thermal (<0.5 eV) neutron flux and the γray dose rate for the moderator of polyethylene, beryllium, graphite and polyethylene with a lead shield. The moderator of polyethylene with a lead shield can fit the condition for irradiation experiments of the thermal neutron flux of greater than several times 108 n/cm2/s and the γ ray dose rate of less than several Gy/h.
Slots for irradiation samples are necessary for a realistic moderator design. We designed moderators with nine slots for cell sample tubes. The slots are located just below the lead layer to gain maximal thermal neutrons under the lead.
We carried out the performance test of the moderator. The thermal neutron flux was measured with the gold foil activation method using foils of 2.5 × 2.5 mm with 10 μm thickness and cadmium shield with the thickness of 0.5 mm which can cover a gold foil. The radioactivity of gold foils was measured after the irradiation with a NaI scintillator and the thermal neutron flux was estimated by calculation using the radioactivity of gold foils and that covered by cadmium covers. The γray dose rates were measured by thermoluminescent dosimeters (TLDs).

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Poster presentation  

Venue：Taipei, Taiwan   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Poster presentation  

Venue：Taipei, Taiwan   Country：Japan  

Event date： 2018.10 - 2018.11

Language：English   Presentation type：Poster presentation  

Venue：Taipei, Taiwan   Country：Japan  

Event date： 2018.10

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：エッサム神田ホール１号館 2Ｆ多目的ホール 201 号室   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋国際会議場   Country：Japan