研究者データベース

金子 純一(カネコ ジユンイチ)
工学研究院 応用量子科学部門 物質量子工学
准教授

基本情報

通称等の別名

    金子純一

所属

  • 工学研究院 応用量子科学部門 物質量子工学

職名

  • 准教授

学位

  • 博士(工学)(東京大学)
  • 経営管理修士(専門職)(小樽商科大学)

J-Global ID

研究キーワード

  • シンチレータ   耐放射線半導体デバイス   放射線医用・医療工学   放射線計測   半導体検出器   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 電子デバイス、電子機器
  • ライフサイエンス / 医用システム
  • エネルギー / 原子力工学

所属学協会

  • 医療物理学会   日本中性子科学会   応用物理学会   ニューダイヤモンドフォーラム   日本原子力学会   

研究活動情報

論文

  • Mingchao Yang, Takehiro Shimaoka, Liwen Sang, Junichi H. Kaneko, Satoshi Koizumi, Meiyong Liao
    FUNCTIONAL DIAMOND 2 1 40 - 45 2022年04月 [査読有り]
  • Takahiro Yamaguchi, Hitoshi Umezawa, Shinya Ohmagari, Hitoshi Koizumi, Junichi H. Kaneko
    APPLIED PHYSICS LETTERS 118 16 2021年04月 [査読有り]
     
    Although the surface conductivity of a hydrogen-terminated diamond (H-diamond) enables production of high-performance field effect transistors (FETs), the total ionizing dose effect is yet to be clarified for H-diamond FETs. We fabricated a RADiation hardened H-terminated Diamond metal-oxide-semiconductor FET (RADDFET) using an oxide gate dielectric deposited at high temperatures. This paper describes its stable operation after 1 MGy irradiation. H-diamond films were prepared using microwave plasma assisted chemical vapor deposition with a p+ layer for reduction of contact resistance. The Al2O3 passivation layer was deposited by atomic layer deposition at 450 degrees C to achieve operation in high-temperature environment; then a RADDFET was fabricated on them using a Ru electrode. Several current-voltage characteristics were compared before irradiation and after certain dose levels up to 1 MGy. Before they were irradiated in air, the dose rate was measured using a cellulose triacetate film dosimeter. Even after an irradiation level of 1 MGy, the off-current at gate bias voltage (V-G) of 3V was more than six orders of magnitude lower than the on-current at V-G of -6V. Variation of the drain current density (J(DS)) in the measurements was less than 2%. The threshold voltage shifted approximately 1.7V with 3 kGy of x ray irradiation, but no marked degradation was confirmed at higher levels. The subthreshold swings were 238, 215, and 264mV/decade, respectively, after irradiation of 100 kGy, 300 kGy, and 1 MGy. These results indicate that the RADDFET was very stable at higher doses after initial stabilization.
  • Takanori Hanada, Shinya Ohmagari, Junichi H. Kaneko, Hitoshi Umezawa
    APPLIED PHYSICS LETTERS 117 26 2020年12月 [査読有り]
     
    We fabricated diamond pseudo-vertical Schottky barrier diodes using a half-inch semi-insulative diamond (100) wafer. Most diodes exhibited a large rectifying ratio (>10(10)) with undetectable leakage current at a reverse bias of 5V (0.6MV cm(-1)), with only 2% of diodes exhibiting an Ohmic-like leakage current. Surface defects were observed under the Schottky barrier diode, and their impacts on electrical properties were analyzed using a Murphy model and correlation factor analysis. We found that most crystalline defects (surface hillocks) were electrically non-active and that non-epitaxial crystallites and process-related field-plate cracks were the main defects that induced a large leakage current. Schottky barrier diodes without such killer defects showed a high electric field strength of similar to 5MV cm(-1).
  • Yuki Morishita, Kenji Izaki, Junichi H. Kaneko, Seiichi Yamamoto, Mikio Higuchi, Tatsuo Torii
    IEEE TRANSACTIONS ON NUCLEAR SCIENCE 67 10 2203 - 2208 2020年10月 [査読有り]
     
    We developed a Gd2Si2O7 (GPS) scintillator-based alpha imaging detector and demonstrated its effectiveness by evaluating the actual Pu particle and Rn-222 progeny. The GPS scintillator plate was prepared by a sintering method. The outer dimensions of the GPS scintillator plate were 5 x 5 cm, and the scintillator layer was approximately 50 mu m on a 3-mmthick high-transparency glass. The plate was optically coupled to a position-sensitive photomultiplier tube (Hamamatsu H8500, Hamamatsu, Japan) with silicone grease. The developed imaging detector exhibited good uniformity; Pu particle activities were accurately evaluated at 14 different positions and the difference in activity was within +/- 6%. The radon-222 progeny counts were reduced by 65.3% by applying an energy window. Although the Pu/Rn-222 progeny activity ratio was 1/51, the Pu particle was successfully identified among the Rn-222 progeny within the 5-min measurement time. The imaging detector has an excellent ability for detecting Pu among the Rn-222 progeny. Thus, this detector is useful for alpha contamination monitoring in high-radon-background environments.
  • Katsunori Ueno, Takahiro Tadokoro, Yuichiro Ueno, Keisuke Sasaki, Satoshi Koizumi, Akiyoshi Chayahara, Yoshiaki Mokuno, Shintaro Hirano, Junichi H. Kaneko
    JAPANESE JOURNAL OF APPLIED PHYSICS 58 10 2019年10月 [査読有り]
     
    We have developed a gamma-ray detector based on a single-crystal diamond in order to improve the heat and radiation resistances of gamma-ray monitors. We fabricated prototypes with two types of diamond grown by a chemical vapor deposition method. The count rates with temperature and accumulated dose were obtained using a Cs-137 gamma-ray source, then the errors at full scale (%FS) were evaluated using a method to reduce the dark count. The prototype-A worked to 643 K within 2.9%FS and to 3.1 MGy within 4.9%FS; on the other hand, the prototype-B worked to 545 K within 3.4%FS and to 5.0 MGy within 0.47%FS. This study demonstrates that the diamond semiconductor was promising for monitoring with enhanced heat and radiation resistances. (C) 2019 The Japan Society of Applied Physics
  • Morishita, Y, Kaneko, J.H, Higuchi, M, Izaki, K, Yajima, T, Matsuura, M, Tamura, K, Torii, T
    Radit. Meas. 122 115 - 120 2019年03月 [査読有り][通常論文]
     
    A dust monitor with a silicon surface barrier detector (SSBD) is introduced at a nuclear fuel facility to detect airborne contamination of Pu-238 and (PU)-P-239 released by past accidents. However, an SSBD frequently produces false alarms, especially in a room with high humidity. To develop a highly reliable dust monitor, we developed an alpha-particle spectrometer based on a cerium-doped Gd2Si2O7 (GPS) scintillator plate and a photomultiplier tube (PMT). The GPS scintillator plate is hexagonal and 50 mm in diameter, and the scintillator layer is approximately 40 mu m. An output signal from the PMT is amplified by a preamp and transferred to an MCA. Then, an energy spectrum is displayed in real time. The (241)AM alpha source, Rn progeny collected on the air filter, and a PuO2 particle were measured by our developed spectrometer. The energy resolution for 5.5-MeV alpha particles was similar to 11.9% +/- 0.2% of the FWHM. The efficiency was 92%, and it had a uniform sensitivity. By applying an energy window, the count-rate of the Rn progeny decreased by 77%. The GPS scintillator plate was able to measure the alpha spectrum even though the GPS scintillator got wet. Therefore, the alpha dust monitor using the GPS scintillator plate is ideal for detecting alpha-particle emitters in places lacking temperature and humidity controls, such as the outside of buildings.
  • Shintaro Hirano, Junichi H. Kaneko, Takanori Hanada, Shogo Ito, Takehiro Shimaoka, Hiroaki Shimmyo, Masakatsu Tsubota, Akiyoshi Chayahara, Yoshiaki Mokuno, Hitoshi Umezawa
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 215 22 2018年11月 [査読有り]
     
    In an effort to enlarge a sensitive area of a diamond radiation energy spectrometer, a self-standing chemical vapor deposition (CVD) single crystal is grown on an 8-mm-square "general grade" CVD single-crystal diamond substrate fabricated by Element Six Ltd. The growth conditions that achieved a mu tau product of 3 x 10(-4) cm(2) V-1 for holes in a CVD single-crystal diamond grown on a high-pressure and high-temperature (HP/HT) type IIa single-crystal diamond substrate elsewhere are adopted. The charge collection efficiency (CCE) of 99.9% for both charge carriers, and 0.39% and 0.5% of energy resolution for holes and electrons are achieved using 5.486 MeV alpha particles. Uniformity of the energy resolution is sufficient for the use of a radiation energy spectrometer. However, mu tau products of (5.0 +/- 0.4) x 10(-5) and (1.8 +/- 0.2) x 10(-5) cm(2) V-1 for holes and electrons are obtained, respectively. These values are approximately one order of magnitude smaller than the mu tau products of the CVD single crystal grown on a HP/HT type IIa diamond substrate using the same growth conditions.
  • Morishita Yuki, Yamamoto Seiichi, Izaki Kenji, Kaneko Junichi H, Hoshi Katsuya, Torii Tatsuo
    RADIATION MEASUREMENTS 112 1 - 5 2018年05月 [査読有り][通常論文]
     
    At the site of the Fukushima Daiichi nuclear power plant (FDNPP), there is a large quantity of beta and gamma emitters such as Sr-90 and Cs-137. Moreover, radon (Rn) progeny, which are naturally occurring radionuclides, exist and emit alpha and beta particles. To detect plutonium isotopes ((PU)-P-238, (PU)-P-239, and Pu-240) in a field of high beta and gamma background, an alpha particle detector with low beta- and gamma-ray sensitivity and good energy resolution for an alpha particle is required to distinguish plutonium isotopes from Rn progeny. Previously, we developed an alpha particle imaging detector by combining a 0.1-mm-thick gadolinium aluminum gallium garnet (GAGG) scintillator with a silicon photomultiplier (SiPM). However, this detector was sensitive to environmental gamma and beta rays. In this study, we optimized the thickness of the GAGG scintillator for alpha particle detection in a field of high beta and gamma background. We prepared three GAGG scintillators with thicknesses of 0.05 mm, 0.07 mm, and 0.1 mm. Each of the GAGG scintillators was coupled optically to the SiPM array, which was used as the photodetector. Alpha, beta, and gamma rays were irradiated onto the developed alpha particle detector, and their spectra were obtained. The energy resolution of the 0.05 mm-thick GAGG for 5.5-MeV alpha particles (similar to 11.6% full width at half maximum [FWHM]) was the best among the three GAGG scintillators. All GAGG scintillators used in this study were not sensitive to gamma rays with a dose rate of 1 mSv/h. The beta particle count above the lower level discriminator (LLD) decreased because the scintillator was thinner, and the beta count of the 0.05-nun-thick GAGG was only 1/100 that of the 0.1-mm-thick GAGG. Because the alpha particle detector with the 0.05-mm-thick GAGG scintillator had low beta and gamma ray sensitivity and good energy resolution for alpha particles, it is promising from the viewpoint of detecting plutonium contamination in a field with high beta and gamma background, such as the FDNPP site.
  • Yuki Morishita, Seiichi Yamamoto, Takumaro Momose, Junichi H. Kaneko, Norio Nemoto
    RADIATION PROTECTION DOSIMETRY 178 4 414 - 421 2018年03月 [査読有り]
     
    Plutonium dioxide (PuO2) is used to fabricate a mixed oxide fuel for fast breeder reactors. When a glove box containing PuO2 fails, such as by rupture of a glove or a vinyl bag, airborne contamination of plutonium (Pu) can occur. If a worker inhales PuO2 particles, they will be continually irradiating their lung tissue with alpha particles, and this could cause lung cancer. The nasal smear and nose blow methods are useful for checking workers for PuO2 intake in the field. However, neither method can evaluate the quantitative activity of Pu. No alpha-particle detector that can be used for direct measurements in the nasal cavity has been developed. For direct and quantitative measurement, it is required that a shape of the detector should be a fine bar which inserts itself in the nose to measure the accurate activity of Pu. Therefore, we developed a nasal monitor capable of directly measuring the activity of Pu in the nasal cavity to estimate the internal exposure dose of a worker. Prismatic-shaped 2 x 2 acrylic light guides were used to compose a detector block, and a ZnS(Ag) scintillator was adhered to the surface of these light guides. Silicon photomultiplier (SiPM) arrays with 8 x 8 channels were used as a photodetector. Actual PuO2 particles were measured using the nasal monitor. The nasal monitor could be directly inserted in the nasal cavities, and the activity distribution of Pu was obtained by the nasal monitor. The average efficiencies in 4-pi were 11.4 and 11.6% for the left and right nasal cavities, respectively. The influence of gamma and beta rays from Cesium-137 (Cs-137) Strontium-90 (Sr-90) on the detection of the alpha particles of Pu was negligible. The difference in the measured Pu activity between the ZnS(Ag) scintillation counter and the nasal monitor was within 4.0%. Therefore, it was considered that the developed nasal monitor could be used in direct Pu determination to estimate the internal exposure dose of workers.
  • Katsunori Ueno, Keisuke Sasaki, Junichi Kaneko
    Transactions of the American Nuclear Society 119 534 - 536 2018年 [査読有り]
  • Yuki Morishita, Seiichi Yamamoto, Kenji Izaki, Junichi H. Kaneko, Norio Nemoto
    RADIATION MEASUREMENTS 103 33 - 38 2017年08月 [査読有り]
     
    We developed a new imaging detector called flexible alpha camera that can identify Pu contamination in narrow spaces at work sites. The thickness of the flexible alpha camera is only similar to 1/5th that of the ZnS(Ag) scintillation detector which is commonly used for detecting Pu contamination, and its efficiency in the 4 pi direction is 42.7% for 5.5-MeV alpha particles. The minimal detectable activity (MDA) is 0.014 Bq measured in 30 min. Four types of PuO2 samples, taken from a duct, bag-in/bag-out port, glovebox glove, and vinyl sheet, were measured by the flexible alpha camera. In a two-dimensional distribution of alpha particles, PuO2 was identified automatically using the "AnalyzeParticle" function in the ImageJ plugin, and its activity was evaluated. When acquisition time increased from 10 min to 30 min, a Pu spot with low activity was identified. To verify the measurement in narrow space, a fume hood to which a PuO2 particle was attached was measured using the flexible alpha camera. Since the flexible alpha camera has the thin-thickness of 12 mm and can obtain two-dimensional distribution and energy spectrum of alpha particles, it is effective for detecting Pu contamination in narrow spaces of equipment. (C) 2017 Elsevier Ltd. All rights reserved.
  • Hitoshi Umezawa, Shinya Ohmagari, Yoshiaki Mokuno, Junichi H. Kaneko
    Proceedings of the International Symposium on Power Semiconductor Devices and ICs 379 - 382 2017年 [査読有り]
     
    Diamond has attracted extensive attention for the next generation semiconductor devices, such as high-power, low-loss and high-frequency devices under high temperature conditions. In this paper, a radiation hardness of diamond unipolar devices such as Schottky barrier diode (SBD) and metal-semiconductor field-effect transistor (MESFET) was discussed. No any degradation of ideality factor or specific on-resistance of diamond SBD was observed even after 10 MGy X-ray irradiation. The breakdown voltage was increased after the irradiation since the leakage current increased. The forward current capability and the transconductance of MESFET were almost constant to the X-ray irradiation.
  • Toyoda S, Higuchi M, Tsubota Y, Kaneko J. H, Tadanaga K
    Optical Materials 70 180 - 183 2017年 [査読有り][通常論文]
     
    Translucent LiCaBO3:Ce thin plates were prepared by liquid phase sintering using LiBO2 as a sintering aid, and their fluorescent and scintillation properties were investigated to examine the possibility to use as neutron scintillator. Since the initial part of the directionally solidified specimen contained a second phase of Ca3B2O6, LiCaBO3 may melt incongruently, and simple melt growth of LiCaBO3:Ce is consequently difficult. Translucent thin plates 300 mu m in thickness were successfully fabricated from LiCaBO3:Ce sintered compacts. Although strong fluorescence with the peak wavelength of 390 nm was observed in photoluminescence measurement, scintillation light yield and detection efficiency by alpha-particle irradiation were rather poor. The diffuse reflectance spectrum of LiCaBO3:Ce revealed existence of an absorption band other than Ce3+ bands in the ultraviolet region. The band may corresponds to defect levels, which interrupt the energy transfer from the conduction band of the host to the 5d level of Ce3+ resulting in the degradation of the scintillation performance. (C) 2017 Elsevier B.V. All rights reserved.
  • Junichi H. Kaneko, Kenji Izaki, Kouhei Toui, Takehiro Shimaoka, Yuki Morishita, Youichi Tsubota, Mikio Higuchi
    RADIATION MEASUREMENTS 93 13 - 19 2016年10月 [査読有り]
     
    An alpha particle detector was developed for continuous air monitoring of radioactive contamination in working chambers at plutonium handling facilities. A 5-cm-square Gd2Si2O7:Ce (cerium-doped gadolinium pyro-silicate, GPS:Ce) mosaic scintillator plate for alpha particle measurements was fabricated from GPS single-crystal grains of around 550 mu m diameter; the GPS grains were made of a GPS polycrystalline body grown using a top seeded solution method. The scintillator layer thickness was approximately 100 gm. The surface filling rate of the GPS grains was ca. 62%. To suppress the influence of non-uniformity of pulse heights of a photomultiplier tube, a central part of empty set 40 mm of a 76-mm diameter photomultiplier tube was used. In addition, 3 mm thick high-transmission glass was used as a substrate of the scintillator plate. The detector achieved energy resolution of 13% for 5.5 MeV alpha particles, detection efficiency of 61% and a radon progeny nuclide reduction ratio of 64.5%. A new alpha particle detector was developed to achieve a high radon progeny nuclide reduction ratio approaching that of a silicon semiconductor detector, with high resistance to electromagnetic noise and corrosion. (C) 2016 Elsevier Ltd. All rights reserved.
  • Yuki Sato, Hiroyuki Murakami, Takehiro Shimaoka, Masakatsu Tsubota, Junichi H. Kaneko
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 834 218 - 222 2016年10月 [査読有り]
     
    The performance of a diamond detector created from a single-crystal diamond grown by chemical vapor deposition was studied for application in detecting charged particles having energies ranging from 100 keV to 2 MeV. Energy peaks of different low-energy ions were clearly observed. However, we observed that the pulse height for individual incident ions decreases with increasing atomic number of the ions. We estimated the charge collection efficiency of the generated charge carriers by the incident charged particles. The charge collection efficiencies are 97.0 +/- 0.7% for 2 MeV helium-ions (He+). On the other hand, compared with that of He+, silicon-ions (Si+) and gold-ions (Au3+) show low charge collection efficiency: 70.6 +/- 2.2% and 29.5 +/- 4.2% for 2 MeV-Si+ and 2 MeV-Au3+, respectively. We also found that the charge collection efficiency decreases as the generated charge density inside the diamond crystal increases. (C) 2016 Elsevier B.V. All rights reserved.
  • Takehiro Shimaoka, Junichi H. Kaneko, Yuki Sato, Masakatsu Tsubota, Hiroaki Shimmyo, Akiyoshi Chayahara, Hideyuki Watanabe, Hitoshi Umezawa, Yoshiaki Mokuno
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 213 10 2629 - 2633 2016年10月 [査読有り]
     
    This report is the first describing experimental evaluation of Fano factor for diamond detectors. High-quality self-standing chemical vapor deposited diamond samples were produced using lift-off method. Alpha-particle induced charge measurements were taken for three samples. A 13.1 +/- 0.07 eV of the average electron-hole pair creation energy and excellent energy resolution of approximately 0.3% were found for 5.486MeV alpha particles from an Am-241 radioactive source. The best Fano factor for 5.486MeV alpha particles, calculated from experimentally obtained epsilon values and the detector intrinsic energy resolution, was 0.382 +/- 0.007. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Yuki Sato, Hiroyuki Murakami, Takehiro Shimaoka, Masakatsu Tsubota, Junichi H. Kaneko
    JAPANESE JOURNAL OF APPLIED PHYSICS 55 4 2016年04月 [査読有り]
     
    We investigate the performance of a charged-particle detector fabricated using single-crystal diamond grown by chemical vapor deposition. The detector identified four different Am-241 alpha-particle energies (5.389, 5.443, 5.486, and 5.545 MeV) thanks to its superior energy resolution of 0.407 +/- 0.004% for electron drift and 0.418 +/- 0.004% for hole drift (full width at half maximum). The charge-collection efficiency inside the diamond crystal was above 97.0% for both electrons and holes. The diamond detector also exhibited no significant degradation in terms of pulse-height spectra and energy resolution during operation for more than 100 h under electron-drift conditions. In contrast, the pulse-height spectra obtained under hole-drift conditions deteriorated because of the polarization phenomenon. (C) 2016 The Japan Society of Applied Physics
  • Takehiro Shimaoka, Junichi H. Kaneko, Masakatsu Tsubota, Hiroaki Shimmyo, Hideyuki Watanabe, Akiyoshi Chayahara, Hitoshi Umezawa, Shin-ichi Shikata
    EPL 113 6 2016年03月 [査読有り]
     
    For stable semiconductor detector operation under harsh environments, an ideal single-crystal diamond without a charge trapping centre is required. For this study, a self-standing single-crystal CVD diamond was fabricated using a lift-off method. The reduction of charge trapping factors such as structural defects, point defects, and nitrogen impurities, was attempted using 0.2% of low-methane concentration growth and using a full metal seal chamber. A high-quality self-standing diamond with strong free-exciton recombination emission was obtained. Charge collection efficiencies were 100.1% for holes and 99.8% for electrons, provided that epsilon(diamond) = 13.1 eV and epsilon(Si) = 3.62 eV. Energy resolutions were 0.38% for both holes and electrons. We produced a high-performance diamond radiation detector using the productive lift-off method. Copyright (C) EPLA, 2016
  • Takehiro Shimaoka, Junichi H. Kaneko, Kentaro Ochiai, Masakatsu Tsubota, Hiroaki Shimmyo, Akiyoshi Chayahara, Hitoshi Umezawa, Hideyuki Watanabe, Shin-ichi Shikata, Mitsutaka Isobe, Masaki Osakabe
    REVIEW OF SCIENTIFIC INSTRUMENTS 87 2 2016年02月 [査読有り]
     
    A self-standing single-crystal chemical vapor deposited diamond was obtained using lift-off method. It was fabricated into a radiation detector and response function measurements for 14 MeV neutrons were taken at the fusion neutronics source. 1.5% of high energy resolution was obtained by using the C-12(n, alpha)Be-9 reaction at an angle of 100 degrees with the deuteron beam line. The intrinsic energy resolution, excluding energy spreading caused by neutron scattering, slowing in the target and circuit noises was 0.79%, which was also the best resolution of the diamond detector ever reported. (C) 2016 AIP Publishing LLC.
  • Masakatsu Tsubota, Junichi H. Kaneko, Daijirou Miyazaki, Takehiro Shimaoka, Katsunori Ueno, Takahiro Tadokoro, Akiyoshi Chayahara, Hideyuki Watanabe, Yukako Kato, Shin-ichi Shikata, Hitoshi Kuwabara
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 789 50 - 56 2015年07月 [査読有り]
     
    We synthesized single-crystal diamonds using microwave assisted plasma chemical vapor deposition and evaluated the temperature dependence of the diamond radiation detectors. We achieved charge collection efficiency of the hole of 96.9% with 3.0% energy resolution at 473 K. In the case of electrons. they became undetectable at temperatures higher than 373 K. It is possible that carrier trapping generated with frequency or the leakage current increased. The detector produced by the diamond in Diamond Detector Ltd. detector, operates normally at 523 K. Electrons can be measured at 573 K. We discussed the characteristics of charge carrier transport in the diamond detector to prepare for future use at higher temperatures. (C) 2015 Elsevier B.V. All rights reserved,
  • Nishikata, M, Ueda, A, Higuchi, M, Kaneko, J.H, Tsubota, Y, Ishibashi, H
    Opt. Mater. 45 156 - 160 2015年07月 [査読有り][通常論文]
     
    Translucent Gd2Si2O7:Ce (GPS:Ce) polycrystalline plates were prepared via liquid-phase sintering using SiO2 as a self-flux, and their scintillation performances for alpha-particles were investigated. Dense sintered compacts comprising large grains, some of which were larger than 100 mu m in diameter, were successfully prepared by sintering at 1690 degrees C for 100 h. The best result was obtained with the powder comprising only <40 mu m particles. Any combination of powders of <40 mu m and <15 mu m resulted in inhomogeneous structures with smaller grains of about 50 mu m. A translucent GPS:Ce thin plate was fabricated by grinding the sintered compact that contained excess SiO2 of 8 mol%. Since the plate was composed of large grains, scattering at the grain boundaries was effectively suppressed and many of the grains virtually act as single crystals when the plate thickness was less than 100 mu m. Therefore, the decrease in the plate thickness brought increase in the total transmission, and light yield and energy resolution were consequently improved. When the plate thickness was 50 mu m, light yield was 82% as compared with that of a GPS:Ce single crystal as a reference, and energy resolution attained to 13%. (C) 2015 Elsevier B.V. All rights reserved.
  • High-temperature scintillation properties of orthorhombic Gd2Si2O7 aiming at well logging
    Tsubota, Y, Kaneko, J.H, Higuchi, M, Nishiyama, S, Ishibashi, H
    Appl. Phys. Express 8 6 062602  2015年06月 [査読有り][通常論文]
  • Yuki Sato, Hiroyuki Murakami, Takehiro Shimaoka, Masakatsu Tsubota, Junichi H. Kaneko
    2015 4TH INTERNATIONAL CONFERENCE ON ADVANCEMENTS IN NUCLEAR INSTRUMENTATION MEASUREMENT METHODS AND THEIR APPLICATIONS (ANIMMA) 2015年 
    The performance of a diamond detector made of a single-crystal diamond grown by chemical vapor deposition was studied for charged particles, having energies ranging from 100 keV to 2 MeV. Energy peaks of these low-energy ions were clearly observed. However, we observed that the pulse height for individual incident ion decreases with increasing atomic number of the ions. We estimated the charge collection efficiency of the generated charge carriers by charged particle incident. The charge collection above similar to 95% is achieved for helium (He) with the energy above 1.5 MeV. On the other hand, the charge collection efficiency for heavy-ions shows lower values compared with that of He+, similar to 70% for silicon (Si+) and similar to 30% for gold (Au3+), at the same incident energy range, respectively.
  • Sato Yuki, Shimaoka Takehiro, Kaneko Junichi H, Murakami Hiroyuki, Isobe Mitsutaka, Osakabe Masaki, Tsubota Masakatsu, Ochiai Kentaro, Chayahara Akiyoshi, Umezawa Hitoshi, Shikata Shinichi
    Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment 784 147 - 150 2015年 [査読有り][通常論文]
  • Shimaoka T, Kaneko J.H, Arikawa Y, Isobe M, Sato Y, Tsubota M, Nagai T, Kojima S, Abe Y, Sakata S, Fujioka S, Nakai M, Shiraga H, Azechi H, Chayahara A, Umezawa H, Shikata S
    Review of Scientific Instruments 86 5 2015年 [査読有り][通常論文]
     
    A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% +/- 0.8% and 97.1% +/- 1.4% for holes and electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 +/- 0.4 x 10(7) cm/s and 1.0 +/- 0.3 x 10(7) cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5-1 keV and neutron yield of more than 109 neutrons/shot. (C) 2015 AIP Publishing LLC.
  • Yuki Morishita, Seiichi Yamamoto, Kenji Izaki, Junichi H. Kaneko, Kohei Toui, Youichi Tsubota, Mikio Higuchi
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 764 383 - 386 2014年11月 [査読有り]
     
    Scintillation detectors for alpha particles are often used in nuclear fuel facilities. Alpha particle detectors have also become important in the research field of radionuclide therapy using alpha emitters. ZnS(Ag) is the most often used scintillator for alpha particle detectors because its light output is high. However, the energy resolution of ZnS(Ag)-based scintillation detectors is poor because they are not transparent. A new ceramic sample, namely the cerium doped Gd2Si2O7 (GPS) scintillator, has been tested as alpha particle detector and its performances have been compared to that one of three different scintillating materials: ZnS(Ag), GAGG and a standard plastic scintillator. The different scintillating materials have been coupled to two different photodetectors, namely a photomultiplier tube (PMT) and a Silicon Photo multiplier (Si-PM): the performances of each detection system have been compared. Promising results as far as the energy resolution performances (10% with PMT and 14% with Si-PM) have been obtained in the case of GPS and GAGG samples. Considering the quantum efficiencies of the photodetectors under Lest and their relation to the emission wavelength of the different scintillators, the best results were achieved coupling the GPS with the PMT and the GAGG with the Si-PM (C) 2014 Elsevier B.V. All rights reserved.
  • Y. Sato, H. Murakami, T. Shimaoka, M. Tsubota, J. H. Kaneko
    EPL 108 4 2014年11月 [査読有り]
     
    The performance of a single-crystal diamond detector, grown by chemical vapour deposition, as an energy spectrometer for charged particles was studied. The detector was able to identify four different energies of (241) Am alpha-particles (5.389, 5.443, 5.486, and 5.545 MeV) thanks to a superior intrinsic energy resolution of similar to 0.4% (full width at half maximum). The electrode configuration, specifically the electric field configuration inside the diamond crystal, and the electrode materials, strongly affect the energy resolution for charged particles. The charge collection efficiency inside the diamond crystal was similar to 97% for both electrons and holes. Copyright (C) EPLA, 2014
  • Yuki Morishita, Seiichi Yamamoto, Kenji Izaki, Junichi H. Kaneko, Kohei Toi, Youichi Tsubota
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 747 81 - 86 2014年05月 [査読有り]
     
    Alpha particles are monitored for detecting nuclear fuel material (i.e., plutonium and uranium) at nuclear fuel facilities. Currently, for monitoring the airborne contamination of nuclear fuel, only energy information measured by Si semiconductor detectors is used to distinguish nuclear fuel material from radon daughters. In some cases, however, such distinguishing is difficult when the radon concentration is high. In addition, a Si semiconductor detector is generally sensitive to noise. In this study, we developed a new alpha particle imaging system by combining a Si PM array, which is insensitive to noise, with a Ce-doped Gd3Al2Ga3O12(GAGG) scintillator, and evaluated our developed system's fundamental performance. The scintillator was 0.1-mm thick, and the light guide was 3.0 mm thick. An Am-241 source was used for all the measurements. We evaluated the spatial resolution by taking an image of a resolution chart. A 1.6 lp/mm slit was clearly resolved, and the spatial resolution was estimated to be less than 0.6-mm FWHM. The energy resolution was 13% FWHM. A slight distortion was observed in the image, and the uniformity near its center was within +/- 24%. We conclude that our developed alpha-particle imaging system is promising for plutonium detection at nuclear fuel facilities. (C) 2014 Elsevier B.V. All rights reserved.
  • Y. Sato, T. Shimaoka, J. H. Kaneko, H. Murakami, D. Miyazaki, M. Tsubota, A. Chayahara, H. Umezawa, S. Shikata
    EPL 106 2 2014年04月 [査読有り]
     
    The response of a diamond detector made from a single crystal grown by chemical vapour deposition was studied using a broadband amplifier. A short pulse width of similar to 1 ns for Am-241-alpha-particles was observed with a digital oscilloscope. To discuss pulse shape distortion from the detector in a measurement system, we simulated waveforms with a SPICE simulator using an equivalent circuit model that contained three main parts: detector, amplifier, and oscilloscope. In the simulation, we found that the pulse width spread by more than 200 ps following amplification. We discuss the effects of the detector read-out circuit time constant on the observed waveforms and confirm that the pulse width spread was restrained by use of a short time constant compared with carrier drift time in diamond crystals. Copyright (c) EPLA, 2014
  • Takehiro Shimaoka, Junichi H. Kaneko, Kenji Izaki, Youichi Tsubota, Mikio Higuchi, Shusuke Nishiyama
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 735 110 - 114 2014年01月 [査読有り]
     
    A scintillator plate with high energy resolution was developed to produce an alpha particle monitor used in nuclear fuel reprocessing plants and mixed plutonium-uranium oxide (MOX) fuel plants. Grains of a Gd2Si2O7 (GPS) scintillator of several 10 to 550 mu m were fixed on a glass substrate and were then mechanically polished. By increasing the size of scintillator grains and removing fine powders, the collected light yield and energy resolution for alpha particles were drastically improved. Energy resolution of 9.3% was achieved using average grain size of 91 mu m. Furthermore, the ratios between counts in a peak and total counts were improved by more than 60% by the further increase of grain size and adoption of mechanically polished surfaces on both sides. Beta and gamma ray influences were suppressed sufficiently by the thin 100 mu m scintillator plates. (C) 2013 Elsevier B.V. All rights reserved.
  • Youichi Tsubota, Junichi H. Kaneko, Mikio Higuchi, Moyuru Minagawa, Hiroyuki Ishibashi
    OPTICAL MATERIALS 36 3 665 - 669 2014年01月 [査読有り]
     
    La-substitute GPS with triclinic structure was grown using a top-seeded solution growth (TSSG) method to reduce concentration quenching by cerium. The low cerium concentration of 2.5% and triclinic crystal seed were chosen for crystal growth. The grown La-GPS single crystal showed light yield that was 1.2 times larger than NaI:Tl. Decay time and energy resolution for 662 keV gamma-rays were, respectively, 90 ns and 7.1%. (C) 2013 Elsevier B.V. All rights reserved.
  • Sato Y, Shimaoka T, Kaneko J. H, Murakami H, Miyazaki D, Tsubota M, Chayahara A, Umezawa H, Shikata S
    Epl 104 2 2013年 [査読有り][通常論文]
     
    The performance of a diamond detector made of single-crystal diamond grown by chemical vapour deposition was studied for heavy ions, having energy of 3MeV. Energy peaks of these low-energy ions were clearly observed. However, the pulse height for individual incident ion decreases with increasing atomic number of the ions. For understanding this pulse height reduction effect, we calculated the amount of ionizing and non-ionizing energy loss of incident ions in the diamond detector. The results of our calculation suggest the contribution of charge loss mechanisms other than the recombination effect of electron-hole pairs produced along the ionized track. We also mentioned the incomplete charge collection near the boundary region between the metal electrode and the diamond surface. Copyright (C) EPLA, 2013
  • Junichi H. Kaneko, Fumiyuki Fujita, Yuta Konno, Takuto Gotoh, Norihiko Nishi, Hideyuki Watanabe, Akiyoshi Chayahara, Hitoshi Umezawa, Nobuteru Tsubouchi, Shinichi Shikata, Mitsutaka Isobe
    DIAMOND AND RELATED MATERIALS 26 45 - 49 2012年07月 [査読有り][通常論文]
     
    As part of the development of diamond radiation detectors for energy spectrometry, quality improvement of CVD diamond single crystals was conducted mainly by measures of single diamond substrates. To suppress stress resulting from unconformity of lattice spacing between a substrate and a grown layer, which sometimes causes breakage, HP/HT type IIa diamond single-crystal substrates were adopted, and it resulted successfully. In addition an off-axis (001) surface was fabricated on the substrate to reduce abnormal growth. A lift-off method was adopted to reuse the HP/HT type IIa substrate with an off-axis (001) surface. Judging from peaks caused by free exciton recombination in cathode luminescence spectra, growth conditions more strongly affected the diamond crystal quality than substrates of any kind. Energy resolution of 0.6% for alpha particles was obtained by one CVD diamond single crystal. Charge collection efficiency of approximately 100% and 95% for holes and electrons was achieved. Step bunching caused by residual gas was observed on the grown CVD diamond surface. From the perspective of charge carriers' transportation measurement, the reduction of residual gas and optimization of growth conditions are indispensable. (c) 2012 Elsevier B.V. All rights reserved.
  • Youichi TSUBOTA, Junichi H. KANEKO, Kaori KONDO, Kenji IZAKI, Mikio HIGUCHI, Takehiro SHIMAOKA, Fumiyuki FUJITA, Shusuke NISHIYAMA
    Progress in Nuclear Science and Technology 3 97 - 99 2012年
  • Tsubouchi N, Mokuno Y, Kakimoto A, Fujita F, Kaneko J. H, Yamada H, Chayahara A, Shikata S
    Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms 286 313 - 317 2012年 [査読有り][通常論文]
     
    Thick (similar to 100 mu m) undoped diamond films were grown homoepitaxially on single crystal (SC) diamond substrates by microwave plasma chemical vapor deposition (CVD). To form a freestanding SC diamond film (plate), the substrate was pre-ion-implanted with high-energy ion beams before the film growth, and after the thick-film deposition, the substrate was eliminated using a lift-off method, resulting in fabrication of a SC CVD diamond plate. Two samples were prepared; sample 1 was grown on a (001) oriented, nitrogen doped CVD SC diamond at similar to 900 degrees C with the input microwave power of 1.7 kW, while sample 2 was grown on a (001) oriented, high-pressure high-temperature synthesized type-1b SC diamond at similar to 900 degrees C with the input microwave power of 1.25 kW. The formed SC plates have high optical transparencies, indicating no remarkable optical absorptions seen in the wavelength from ultraviolet to near infrared. The photoluminescence (PL) spectra of both samples show strong free exciton FE peaks, while in sample 2 relatively strong optical emissions corresponding to nitrogen related centers were observed in the visible region. After the metal electrodes were formed on both faces of the SC diamond plate to fabricate a sandwich-type diamond particle detector, the energy spectra of 5.486 MeV alpha-particles from Am-241 were measured. The charge collection efficiencies (CCEs) of sample 1 were CCE = 98% for a hole transport and CCE = 89% for an electron transport, respectively, while CCEs of sample 2 were CCE = 80% for a hole transport and CCE = 78% for an electron transport, respectively. These results indicate that both holes and electrons in sample 2 were trapped much more than those in sample 1. Possible candidates of carrier capture centers are nitrogen and/or nitrogen-vacancy centers observed in PL, nonradiative defect (complex) centers, extended defects such as threading dislocations observed in micrographs taken with polarizers. The different growth conditions most likely affected crystallinity and responses to alpha-particles of the samples. (C) 2011 Elsevier B.V. All rights reserved.
  • Tsubouchi N, Mokuno Y, Kakimoto A, Konno Y, Yamada H, Chayahara A, Kaneko J. H, Fujita F, Shikata S
    Diamond and Related Materials 24 74 - 77 2012年 [査読有り][通常論文]
     
    Crystallinity of a freestanding large (size: similar to 9 x 7 mm) undoped single crystal (SC) diamond film grown by plasma chemical vapor deposition (CVD) and radiation response of a sandwich-type radiation detector made from this SC plate to a particles were investigated. The freestanding SC film was formed by elimination of a substrate using a so-called "lift-off method" after the growth of a thick-film on a pre-ion-implanted substrate. The formed SC plate has a high optical transparency, indicating no remarkable optical absorption seen in the wavelength from ultraviolet to near-infrared region. In the energy spectra of 5.486 MeV alpha-particles, relatively sharp peaks were observed for both hole and electron transits. For the hole transit, the peak resolution of the pulse height distribution and charge collection efficiency (CCE) were similar to 0.7% and 98%, respectively. On the other hand, for the electron transit, the peak resolution and CCE obtained were similar to 4.4% and 89%, respectively. In the photoluminescence spectrum at room temperature, a strong sharp peak around 235 nm corresponding to free exciton and a weak visible band mainly related to nitrogen-vacancy complex were observed. The spectral width of the (004) plane X-ray rocking curve was 16.5 ''. The micrograph taken using crossed-polarizers demonstrated that there are some white regions and four-petaled patterns, originating from internal strain and most likely threading dislocations, respectively. (C) 2011 Elsevier B.V. All rights reserved.
  • Hiroki Shirato, Rikiya Onimaru, Masayori Ishikawa, Jun-ichi Kaneko, Tsuguhide Takeshima, Kenta Mochizuki, Shinichi Shimizu, Kikuo Umegaki
    CANCER SCIENCE 103 1 1 - 6 2012年01月 [査読有り][通常論文]
     
    Respiratory motion considerably influences dose distribution, and thus clinical outcomes in radiotherapy for lung cancer. Breath holding, breath coaching, respiratory gating with external surrogates, and mathematical predicting models all have inevitable uncertainty due to the unpredictable variations of internal tumor motion. The amplitude of the same tumor can vary with standard deviations >5 mm occurring in 23% of T12N0M0 non-small cell lung cancers. Residual motion varied 16 mm (95th percentile) for the 40% duty cycle of respiratory gating with external surrogates. The 4-D computed tomography is vulnerable to problems relating to the external surrogates. Real-time 4-D radiotherapy (4DRT), where the temporal changes in anatomy during the delivery of radiotherapy are explicitly considered in real time, is emerging as a new method to reduce these known sources of uncertainty. Fluoroscopic, real-time tumor-tracking technology using internal fiducial markers near the tumor has +/- 2 mm accuracy, and has achieved promising clinical results when used with X-ray therapy. Instantaneous irradiation based on real-time verification of internal fiducial markers is considered the minimal requisite for real-time 4DRT of lung cancers at present. Real-time tracking radiotherapy using gamma rays from positron emitters in tumors is in the preclinical research stage, but has been successful in experiments in small animals. Real-time tumor tracking via spot-scanning proton beam therapy has the capability to cure large lung cancers in motion, and is expected to be the next-generation real-time 4DRT. (Cancer Sci 2012; 103: 16)
  • Improvement of crystal quality of a homoepitaxially grown diamond layer by a plasma etching treatment for a diamond substrate
    PROGRESS IN NUCLEAR SCIENCE AND TECHNOLOGY 1 255 - 258 2011年 [査読無し][通常論文]
  • Luminescence properties and Crystal structures of Pr-doped gadolinium pyrosilicate
    PROGRESS IN NUCLEAR SCIENCE AND TECHNOLOGY 288 - 291 2011年 [査読無し][通常論文]
  • Improvmement of scintillation characteristics of FZ growth Ce:GPS crystals by annealing in air
    PROGRESS IN NUCLEAR SCIENCE AND TECHNOLOGY 1 279 - 281 2011年 [査読無し][通常論文]
  • M. Isobe, H. Yamanishi, M. Osakabe, H. Miyake, H. Tomita, K. Watanabe, H. Iwai, Y. Nomura, N. Nishio, K. Ishii, J. H. Kaneko, J. Kawarabayashi, E. Takada, A. Uritani, M. Sasao, T. Iguchi, Y. Takeiri, H. Yamada
    REVIEW OF SCIENTIFIC INSTRUMENTS 81 10 10D310-1-10D310-5  2010年10月 [査読有り][通常論文]
     
    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 gamma-ray diagnostics. (C) 2010 American Institute of Physics. [doi:10.1063/1.3492383]
  • F. Fujita, A. Kakimoto, J. H. Kaneko, N. Tsubouchi, Y. Mokuno, A. Chayahara, K. Sato, Y. Konno, A. Homma, S. Shikata, M. Furusaka
    DIAMOND AND RELATED MATERIALS 19 2-3 162 - 165 2010年02月 [査読有り][通常論文]
     
    Using lift-off method, we synthesized large self-standing plasma CVD diamond films on various substrates. Charge carrier transportation in diamond was measured using alpha particle measurements and TOF methods with a short-pulsed UV laser. The high-quality films were synthesized rapidly. We observed the maximum transit time of holes and electrons shorter than 5 ns. The lift-off method is useful to fabricate the high-quality diamond with excellent drift velocities of the charge carrier. The charge transport characteristics of our diamond films are comparable to those of a commercially available (Element Six Ltd.) electronics grade Ila diamond single crystal. (C) 2009 Elsevier B.V. All rights reserved.
  • Sohan Kawamura, Mikio Higuchi, Junichi H. Kaneko, Shusuke Nishiyama, Jun Haruna, Shohei Saeki, Shunsuke Ueda, Kazuhisa Kurashige, Hiroyuki Ishibashi, Michihiro Furusaka
    CRYSTAL GROWTH & DESIGN 9 3 1470 - 1473 2009年03月 [査読有り][通常論文]
     
    The melting and solidification behavior of the (Gd0.9Ce0.1)(2)Si2O7 (Ce:GPS) which shows attractive scintillation performance was investigated by means of the slow cooling floating zone (SCFZ) method. Although Ce:GPS melts incongruently, the peritectic composition is estimated to be very close to the GPS composition, less than 67.0 mol % of SiO2 in the (Gd,Ce)(2)O-3-SiO2 system. Constitutional supercooling occurred when approximately 70% volume of the melt was solidified, consequently, the lamellar structure consists of Ce:GPS and the amorphous phase was obtained. On the basis of our study, it is estimated that a volume of 70% of the starting material, whose composition is SiO2 = 67 mol % in the (Gd,Ce)(2)O-3-SiO2 system at Ce 10 mol %, can be solidified as the GPS phase using top-seeded solution growth (TSSG) with the self-flux of SiO2.
  • S. Fukumoto, A. Homma, J. H. Kaneko, Y. Nishibayashi, Y. Yamamoto, A. Ueda, F. Fujita, S. Kawamura, K. Sato, T. Imai, M. Furusaka
    DIAMOND AND RELATED MATERIALS 18 2-3 287 - 291 2009年02月 [査読有り][通常論文]
     
    Electron emission characteristics of needle-type semiconductor diamond electron emitters with pulsed bias operation were evaluated. An X-ray generation experiment was performed. Fowler-Nordheim plotting confirmed that field emission completely governed the electron emission. Maximum emission current of 4.2 mA was achieved using an n-type diamond needle. The needle tip, with area smaller than 1 mu m(2), had estimated electron emission density greater than 4.2 x 10(5) A/cm(2). The effective emission area obtained from the Fowler-Nordheim plot was several 10(-13) cm(2). For adopting and emission area of 1 X 10(-12) cm(2), the estimated electron emission density was higher than 4.2 x 10(9) A/cm(2). Furthermore, the average emission current was 0.5-0.6 mA. This large electron emission was continued for several seconds and repeatable. A threshold electric field existed for electron emission higher than 50 kV/mm; pulsed electron emissions of less than 30 ms were created by slow triangular waveform shaped bias voltage supplied at frequencies of 5-10 Hz. An improved vacuum level and pulsed bias operation prevented damage to diamond electron emitters and steady electron emission better than with thermoelectronic emission and high bias voltage supply in DC mode; continuous X-ray generation of 1 h was achieved. (C) 2008 Elsevier B.V. All rights reserved.
  • Kawamura S, Kaneko, J.H, Higuchi, M, Haruna, J, Saeki S, Fujita, F, Homma, A, Nishiyama, S, Ueda, S, Kurashige K, Ishibashi, H, Furusaka, M
    IEEE Trans. Nucl. Sci. 56 1,Pt.2 328 - 330 2009年 [査読有り][通常論文]
     
    Cerium-doped gadolinium pyrosilicate single crystals Ce : Gd2Si2O7 (Ce:GPS) with various Cc concentrations of 2.5-30 mol% with respect to the total rare-earth sites were prepared by the floating zone method. Their scintillation performances were investigated under irradiation of gamma rays of Cs-137. The Ce concentration dependence of scintillation characteristics and high-performance scintillation characteristics were obtained: 3-6 times greater light output than that of BGO single crystals, rapid decay, and good energy resolutions of 5.1-8.4%. Furthermore, X-ray diffraction patterns of Ce:GPS revealed Ce concentration dependence of the crystal structure of Ce:GPS.
  • Junichi H. Kaneko, Tokuyuki Teraji, Takahiro Imai, Yuuki Hirai, Satoshi Yoshizaki, Kei Satou, Souhan Kawamura, Yusuke Oshiki, Fumiyuki Fujita, Akira Homma, Toshimichi Ito, Michihiro Furusaka
    JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY Supplement 5 391 - 394 2008年06月 [査読有り][通常論文]
     
    Radiation detectors were fabricated with layered structure diamonds comprising several micrometers of a boron-doped single crystal diamond and 20 mu m of insulating single crystal diamond layers grown on a HP/HT-type Ib diamond single crystal Substrate. To improve the yield rate of CVD diamond radiation detectors this approach was adopted. The detectors had rectification characteristics because of their boron-doped diamond contact and aluminum Schottky contact. The leakage current of one detector was less than 0.2 pA at reversed bias voltage of +50 V Energy resolutions of 2.6% and 2.8% for alpha particles from Am-241 were achieved using these detectors. The rise time of a leading edge of an Output signal from one detector was less than 20 ns, which was the fastest rise time of the measurement system; drift velocities of charge carriers were estimated to be faster than 1 x 10(5) cm/s. In addition, cathode luminescence spectra of insulating diamond layers were measured; peaks caused by free exciton recombination and 'band A' were observed. Improved crystallinity of the boron-doped diamond layer helps realization of a layered-type diamond radiation detector with higher energy resolution.
  • OSHIKI Y, KANEKO J.h, FUJITA F, HOMMA A, WATANABE H, MEGURO K, YAMAMOTO Y, IMAI T, SATO K, TSUJI K, KAWAMURA S, FURUSAKA M
    Diamond and Related Materials 17 4-5 833 - 837 2008年04月 [査読有り][通常論文]
     
    Charge carrier dynamics in CVD homoepitaxial diamond thin films were evaluated. Thicknesses of these thin diamond films were 4.5-14 mu m. Measurement was carried out using a fast TOF system with time resolution of 150 ps. This system adopted the localized irradiation mechanism of a 213-nm UV pulsed laser. Induced current caused by charge carrier motion was simulated by a one-dimensional approximation. Then measured signals were analyzed using the physical model of induced current that was confirmed through the simulation. The best lifetimes, T, of electrons and holes in evaluated diamond films were 1.8 +/- 0.3 ns for both charge carriers. However, drift velocities and mean free paths of trapping were not determined because insufficient charge carriers arrived at the further side electrode without trapping. (C) 2008 Elsevier B.V. All fights reserved.
  • S. Fukumoto, A. Honma, J. H. Kaneko, Y. Nishibayashi, A. Ueda, Y. Yamamoto, T. Imai, F. Fujita, S. Kawamura, M. Furusaka
    DIAMOND AND RELATED MATERIALS 17 4-5 764 - 767 2008年04月 [査読有り][通常論文]
     
    Emission currents and other characteristics of needle type diamond electron emitters were evaluated for application to diamond X-ray sources. The evaluation system consisted of a Pyrex glass vacuum chamber, a turbo molecular pump, and a - 50 kV high-voltage supplier. A needle type phosphorus-doped semiconductor diamond electron emitter was kept at 600 degrees C by ohmic heating in a vacuum environment; emission current of ca. 1.1 mu A was observed with bias voltage of - 50 W In addition, the electron orbit and intensity were estimated using an electron optics and electron gun design program 'EGUN'. Great differences were apparent between experimental and calculated results: 64 mu A electron emission current. This result was probably the result of a change in the shape of the tip of the diamond electron emitter. X-rays were generated using electrons from the diamond electron emitter with a tungsten target; energy spectra of the generated X-rays were measured. Then fluoroscopy was carried out. (C) 2008 Elsevier B.V. All rights reserved.
  • H. Ohshita, H. Iwasaki, J. Kaneko, H. Kiyamura, M. Nakao, A. Ochi, K. Ochiai, T. Takeshita, S. Tanaka
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 587 2-3 259 - 265 2008年03月 [査読有り][通常論文]
     
    Thin Gap Chambers (TGCs) will be used as a muon trigger device in the end-cap regions of the ATLAS detector. The detector will be placed in an experimental cavern approximately 100 m below the ground surface. A large amount of neutron background is expected in the cavern. Recoiled nuclei, mostly protons, emerging from the neutron interaction provide a much larger energy deposit in the gas volume than that of the minimum ionizing particle (MIP). This might cause aging and improper operation of the TGC. In order to investigate such influences, we performed a test on the operation stability of a real-use TGC under a much higher neutron flux environment than that expected in the ATLAS cavern. This paper describes the experimental results of the irradiation test using 14-MeV neutrons. The maximum flux was 3.2 x 10(5) HZ/cm(2), Which was effectively approximately nine times higher than that at the worst TGC location. It was proved that the TGC was immune to such a flux and instantaneous large signals originating from the neutrons. The mean output charge from the recoil proton at the nominal operation voltage was found to be approximately 30 times larger than that of MIP. The total fluence was 1.4 x 10(10) neutrons/cm(2), up to which the TGC operated stably and no detector deterioration was observed. This corresponds to approximately nine months of ATLAS operation at the nominal luminosity of 10(34) cm(2)/S. (C) 2008 Elsevier B.V. All rights reserved.
  • Sohan Kawamura, Junichi H. Kaneko, Mikio Higuchi, Fumiyuki Fujita, Akira Homma, Jun Haruna, Shohei Saeki, Kazuhisa Kurashige, Hiroyuki Ishibashi, Michihiro Furusaka
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 583 2-3 356 - 359 2007年12月 [査読有り][通常論文]
     
    As a novel scintillation material, the use of Ce-doped Gd(2)Si(2)O(7) was investigated. In fact, (Gd(0.9)Ce(0.1))(2)Si(6)O(7) powder showed about 1.2 times greater light output than Gd(2)SiO(5) (GSO) single crystals for alpha particles of (241)Am. Furthermore, a fast decay constant of 52 ns was obtained for alpha-particles of (241)Am. Relations between the Ce concentration, crystal structure, and luminescence characteristics were also elucidated. Results of these studies show that heavy Ce doping alters the Gd(2)Si(2)O(7) crystal structure and that the luminescence intensity is dependent not on Cc concentration, but on the triclinic structure formed by heavy Cc doping. (c) 2007 Elsevier B.V. All rights reserved.
  • S. Kawamura, J. H. Kaneko, M. Higuchi, T. Yamaguchi, J. Haruna, Y. Yagi, K. Susa, F. Fujita, A. Homma, S. Nishiyama, K. Kurashige, H. Ishibashi, M. Furusaka
    IEEE TRANSACTIONS ON NUCLEAR SCIENCE 54 4 1383 - 1386 2007年08月 [査読有り][通常論文]
     
    Growth of cerium-doped gadolinium pyrosilicate (Ce:Gd2Si2O7) single crystals, which show 2.5 times greater light output for gamma-rays and five times greater light output for alpha-particles than GSO single crystals, is accomplished using the floating zone growth method (FZ method). Although growth of Gd2Si2O7 (GPS) single crystal is considered to be difficult because it melts incongruently according to the phase diagram of Gd2O3-SiO2 system, we attempted crystal growth of Ce:GPS because of the possibility that heavy Ce doping would change the phase diagram. Transparent single crystals were obtained, although some cracks were observed in the crystals. The crystal structure was triclinic with P/1 space group and density of 5.5 g/cm(3). Two peaks, which were observed using photoluminescence spectrometry at 372 nm and 394 nm, were attributed to 5d-4f transition in Ce3+ ion. Decay times of Ce:GPS scintillation were 46 ns for gamma-ray excitation and 39 ns for alpha-particle excitation. We consider that fabrication of crack free crystals will improve the energy resolution.
  • J. H. Kaneko, T. Taniguchi, S. Kawamura, K. Satou, F. Fujita, A. Homma, M. Furusaka
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 576 2-3 417 - 421 2007年06月 [査読有り][通常論文]
     
    Radiation detectors were fabricated using single and polycrystalline cubic boron nitride (cBN) crystals synthesized using a high-pressure and high-temperature (HP/HT) method. Although cBN single crystals obtained using a barium BN solvent system were nearly colorless and displayed high electrical resistance, in contrast to conventional amber-colored crystals, the single crystals exhibit a leakage current that renders them unsuitable for use in a detector. In contrast, a detector made of a cBN polycrystal synthesized by direct transformation had a very low leakage current of 0.2pA with bias voltage of 100V; it functioned as a radiation detector. From an experiment using alpha-particles, holes traversed a longer distance than electrons. It had a fast rise time of approximately 300ns. The detector also showed sensitivity to neutrons. However, output signals were smaller than the expected voltage from the experiment using alpha-particles, probably because of charge accumulation from the high-neutron flux. (C) 2007 Elsevier B.V. All rights reserved.
  • F. Fujita, Y. Oshiki, J. H. Kaneko, A. Homma, K. Tsuji, K. Meguro, Y. Yamamoto, T. Imai, H. Watanabe, T. Teraji, S. Kawamura, M. Furusaka
    DIAMOND AND RELATED MATERIALS 15 11-12 1921 - 1925 2006年11月 [査読有り][通常論文]
     
    A fast TOF measurement system with 150 ps time resolution for transport behavior of free charge carriers in an intrinsic diamond film by using a UV pulsed laser was developed. The 213 nm UV laser light narrowed to approximately 80 mu m widths could locally create hole-electron pairs in selected locations on a diamond film between two parallel electrodes on the surface. This system measured accurate charge transport characteristics in a diamond film, because created charge carriers moved in a part of the diamond film where they did not get any influence from the laser irradiation. Diamond samples used for verification of the TOF system were intrinsic CVD diamond films with thickness between 4 and 10 mu m grown on HP/HT diamond substrates. Transit time of holes for one diamond film was 4.7 ns with a traverse distance of 250 mu m. The local irradiation of laser made it possible to measure transport characteristics of electrons and holes separately. In addition, it substantially reduced the influence of photoelectron, because the laser beam did not irradiate electrodes. Through several examinations, excellent reliability of the TOF system was confirmed. (c) 2006 Elsevier B.V. All rights reserved.
  • S. Kawamura, J. H. Kaneko, H. Fujimoto, Y. Otake, F. Fujita, A. Homma, T. Sawamura, P. Mikula, M. Furusaka
    PHYSICA B-CONDENSED MATTER 385-86 1277 - 1279 2006年11月 [査読有り][通常論文]
     
    Variations of the Bragg diffraction angle induced by electric fields on piezoelectric single crystal were investigated with the aim of exploiting such crystals for novel neutron devices. A (1-x)(Pb(Mg1/3Nb2/3)O-3)-x(PbTiO3) (PMN-PT) single crystal With strong piezoelectric characteristics was used in the experiment. The sample was poled along < 001 > direction before the experiment. In the course of diffraction measurements, a 0.3 degrees change was observed in the diffraction angle at the maximum induced by the electric field. The diffraction angle variation shows time-dependent behavior, which can be well described using a single exponential decay limited to a saturated value. This effect is considered a result of a change of the domain structure brought about through long-term application of an electric field for several hours. The obtained preliminary results confirmed the possibility of using a ferroelectric crystal as a neutron optical device. (c) 2006 Elsevier B.V. All rights reserved.
  • Y. Oshiki, J. H. Kaneko, F. Fujita, K. Hayashi, K. Meguro, A. Homma, S. Kawamura, Y. Yokota, Y. Yamamoto, K. Kobashi, T. Imai, T. Sawamura, M. Furusaka
    DIAMOND AND RELATED MATERIALS 15 10 1508 - 1512 2006年10月 [査読有り][通常論文]
     
    Drift velocities of charge carriers in polycrystalline diamonds were measured by a self-triggered time-of-flight (TOF) method with alpha particles based on a radiation measurement technique. Based on these measured results, a synthesis method for polycrystalline diamond was verified, and the electric properties of polycrystalline diamonds were improved; drift velocity was increased from 5 x 10(2) to 3 x 10(4) cm/s. The mean free paths (MFPs) of capture of charge carriers in a CVD single crystal diamond was obtained by induced charge distribution measurements with alpha particles, and drift velocity was measured by another TOF method using. a UV pulsed laser. MFPs of capture of electron and hole in a CVD single crystal diamond were determined to be 5.4 and 9.6 mu m, respectively; the hole and electron drift velocities were 5 x 10(5) cm/s and 3 x 10(5) cm/s in an electric field of 24.4 kV/cm, respectively. For diamond, short transit times of several nanoseconds and short MFPs of capture in several micrometers were successfully obtained for the first time by combining of these methods. (c) 2005 Elsevier B.V. All rights reserved.
  • Atsuhiko Ochi, Hironori Kiyamura, Junichi Kaneko, Hidetoshi Ohshita, Tohru Takeshita, Shuji Tanaka, Hiroyuki Iwasaki, Kentaro Ochiai, Makoto Nakao
    REVIEW OF SCIENTIFIC INSTRUMENTS 77 10 10E709  2006年10月 [査読有り][通常論文]
     
    Thin gap chamber (TGC) is a very thin multiwire proportional chamber of only a few millimeters. It has a quick response (about 20 ns), and its production costs are relatively low. TGCs have been used as large area detectors in high energy physics such as Large Electron-Positron collider (LEP) and will be used in the Large Hadron collider (LHC) experiment. However, the characteristics of TGCs under neutrons are not yet clearly understood. As the energy deposits of several MeV neutrons in TGCs are large, the possible effect of these deposits on the operation of the detector is a concern. We studied TGC performance in relation to efficiency, charge distribution, and operation stability using several gas mixtures (CO2/n-pentane and CF4/n-pentane) with 2.5 and 14 MeV neutron sources at Fusion Neutronics Source (FNS) in Japan Atomic Energy Agency. Operation stability using a CF4 based gas was more than 100 times greater than with CO2 based gas, while the minimum ionizing particle signal gain was almost the same. The detection efficiencies were around 0.1% (14 MeV) and 0.02% (2.5 MeV). These results are consistent with our simulation studies. (c) 2006 American Institute of Physics.
  • M Wakisaka, J Kaneko, F Fujita, K Ochiai, T Nishitani, S Yoshida, T Sawamura
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 554 1-3 347 - 355 2005年12月 [査読有り][通常論文]
     
    The process of neutron leaking from a 14 MeV neutron source facility was analyzed by calculations and experiments. The experiments were performed at the Fusion Neutron Source (FNS) facility of the Japan Atornic Energy Institute, Tokai-mura, Japan, which has a port on the roof for skyshine experiments, and a 3 He counter surrounded with a polyethylene moderator of different thicknesses was used to estimate the energy spectra and dose distributions. The He-3 counter with a 3-cm-thick moderator was also used for dose measurements, and the doses evaluated by the counter Counts and the calculated count-to-dose conversion factor agreed with the calculations to within similar to 30%. The dose distribution was found to fit a simple analytical expression, D(r) = Q(D) exp(-r/lambda(D))/r and the parameters Q(D) and lambda(D) are discussed. (c) 2005 Published by Elsevier B.V.
  • K Tsuji, K Hayashi, JH Kaneko, F Fujita, A Homma, Y Oshiki, T Sawamura, M Furusaka
    DIAMOND AND RELATED MATERIALS 14 11-12 2035 - 2038 2005年11月 [査読有り][通常論文]
     
    UV position-sensitive sensor using a polycrystalline highly-oriented diamond film with a sensitive area of 2 x 4.5 mm(2) developed, and a proof-of-concept Study was conducted. The charge division method was employed to establish the position when the light hits the sensitive area. A fifth higher harmonic of a Nd:YAG laser with pulse width of 100 ps was used as a light source. The position resolution was 0.25 mm, and there was good position linearity throughout the sensitive area. Considering the possibility of light-spot broadening due to diffraction by the slit, the sensor may have a better resolution than that indicated by the result. But the electric-field strength of some parts of the crystal was insufficient, the response time was relatively slow, approximately 0.5 ins. (c) 2005 Elsevier B.V. All rights reserved.
  • JH Kaneko, T Tanaka, S Kawamura, Y Oshiki, K Tsuji, M Katagiri, K Ochiai, T Nishitani, F Fujita, T Sawamura, T Iida, M Furusaka
    DIAMOND AND RELATED MATERIALS 14 11-12 2027 - 2030 2005年11月 [査読有り][通常論文]
     
    Radiation detector was made of a high-quality CVD polycrystalline diamond composed of frost column like structure diamond grains, and induced charge distribution spectra and drill velocities were measured by using alpha particles. As a result, the CVD polycrystalline achieved maximum induced charge of 83% of HP/HT type IIa diamond. Moreover, the CVD crystal had lower charge loss on electrons compared with the HP/HT type IIa diamond. Drift velocities of electrons and holes were nu(e)=7.7 x 10(4) and nu(h)=7.3 x 10(4) cm/s at an electric field of 20 kV/cm, respectively. In addition, response function measurement for 14 MeV neutrons was carried Out. (c) 2005 Elsevier B.V. All rights reserved.
  • T Tanaka, JH Kaneko, Y Kasugai, M Katagiri, H Takeuchi, T Nishitani, T Iida
    DIAMOND AND RELATED MATERIALS 14 11-12 2031 - 2034 2005年11月 [査読有り][通常論文]
     
    Radiation tolerance of a type IIa synthetic diamond detector was examined from irradiation of mono-energetic 14 MeV neutrons. Measurements of I-V (current-voltage) characteristics and energy spectrum for 5.486 MeV alpha particles were performed after neutron irradiation. In the I-V characteristics measurement, enhancement of rectification was observed after neutron irradiation of up to 2.0 x 10(12) n/cm(2). Concurrently with the enhancement of rectification, significant decrease in signal amplitude was observed in energy spectrum measurement for alpha particles. It is considered that these changes were due to increase in the concentration of defects acting as shallow energy levels in the forbidden band. For neutron irradiation of higher than 1.6 x 10(13) n/cm(2), weakening of the rectification characteristics and recovery of the signal amplitude were observed. These changes imply that deep energy levels, which were also considered to be introduced by defects, were dominant and weakened the effects of the shallow energy levels. Increase in the concentration of the deep trapping levels resulted in gradual decrease of the signal amplitude and degradation in the energy resolution. The peak for the alpha particles was obtained up to 5.5 x 10(13) n/cm(2). (c) 2005 Elsevier B.V. All rights reserved.
  • F Fujita, A Homma, Y Oshiki, JH Kaneko, K Tsuji, K Meguro, Y Yamamoto, T Imai, T Teraji, T Sawamura, M Furusaka
    DIAMOND AND RELATED MATERIALS 14 11-12 1992 - 1994 2005年11月 [査読有り][通常論文]
     
    There are continuing efforts of developing faster FETs and diamond is one of the strong candidates as a base semiconductor. Since the upper-limit-frequency of diamond FETs determines saturated drift velocities of charge-carriers, we need to first characterize diamond to develop better FETs. It is, however, not easy to measure the velocities with response time of less than 20 ns. Therefore, we developed a drift velocity measurement system using a time-of-flight (TOF) technique with a UV laser with 100 ps pulse width. In order to realize response times faster than 20 ns, we employed a 50 Omega coaxial cable as a load, with which we could effectively reduce the stray capacitance and inductance, and also, suppress reflections in the signal which gives false signals. As a result, we can measure carrier-transit times shorter than 10 ns. (c) 2005 Elsevier B.V. All rights reserved.
  • M Ishikawa, H Kumada, K Yamamoto, J Kaneko, G Bengua, H Unesaki, Y Sakurai, K Tanaka, T Kosako
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 551 2-3 448 - 457 2005年10月 [査読有り][通常論文]
     
    A wide range thermal neutron detector was developed based on the Scintillator with Optical Fiber (SOF) detector which has been previously used for thermal neutron monitoring during boron neutron capture therapy irradiation. With this new detector system we intended to address the issues of real-time thermal neutron flux measurement and the simultaneous measurement of a wide range of thermal neutron flux in a BNCT irradiation field which were difficult to implement with the gold wire activation method. The dynamic range of linearity of the SOF detector was expanded by using a plastic scintillator with a rapid decay time. On the other hand, the contribution of gamma rays and fast neutrons in the measured signals were compensated from those obtained by a pair of SOF detectors, one with a (LiF)-Li-6 neutron converter and the other without. The discrimination level for the measured signals was also optimized to further reduce the contribution of gamma rays and fast neutrons signals. A non-paralyzable system model was applied to correct for the dead-time in the detector system. A good agreement between the thermal neutron flux measured by the gold wire activation method and the paired SOF detector system was observed. However, measurements which would normally take a few days to perform with the gold wire activation method were obtained in just about 15 min using the SOF detector system. We also confirmed the dynamic range of linearity for the SOF detector system to be in the order of magnitude of 10(4). (c) 2005 Elsevier B.V. All rights reserved.
  • JH Kaneko, T Teraji, Y Hirai, M Shiraishi, S Kawamura, S Yoshizaki, T Ito, K Ochiai, T Nishitani, T Sawamura
    REVIEW OF SCIENTIFIC INSTRUMENTS 75 10 3581 - 3584 2004年10月 [査読有り][通常論文]
     
    Response function measurement of layered-type chemical vapor deposition single crystal diamond radiation detectors for 14 MeV neutrons was carried out. The detector had a layered structure that was composed of a boron-doped diamond layer of 0.5 mum in thickness and a nondoped diamond layer of 20 mum on an inexpensive high pressure and high temperature-type Ib diamond substrate. The detector had energy resolution of 2.6% for 5.5 MeV alpha particles. This experiment was mainly carried out in order to understand the present status of the detector as a 14 MeV neutron spectrometer and an extent of charge trapping. As result, a peak caused by the C-12(n,alpha(0))Be-9 reactions was clearly observed; the best energy resolution of 6% as for a synthetic diamond radiation detector was achieved. Detection efficiency was 3.2x10(-7) counts/unit neutron fluence. However, taking the energy resolution for alpha particles, etc., into account, the energy resolution for 14 MeV neutrons was not so high. Further improvement based on better crystal growth is indispensable. (C) 2004 American Institute of Physics.
  • JH Kaneko, Y Otake, H Fujimoto, S Kawamura, M Watanabe, F Fujita, T Sawamura, P Mikula, M Furusaka
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 529 1-3 166 - 168 2004年08月 [査読有り][通常論文]
     
    A principle verification experiment of neutron electric optical devices using piezoelectric single crystals was carried out. This neutron electric optical device can change its d-spacing by applying an electric field to the crystal, which results in change of the Bragg diffraction angle. Although an alpha-quartz has a small piezoelectric strain constant, an alpha-quartz was used in this experiment because characteristics of alpha-quartz are well known and it is easy to obtain high quality and large size single crystals. At first, macroscopic distortion and change of thickness caused by an applied electric field were observed by using laser interferometers. Thus, double crystal diffraction measurement using 4.7 Angstrom cold neutrons was carried out. For these experiments, DC bias voltage was applied to the crystal. As a result, peaks of rocking curves were shifted 14s at 500 V and 2 min at 1000 V from their original positions. These values were approximately one figure larger than the theoretical values; therefore, these results were influenced by macroscopic bending of the crystal. From these results, it can be concluded that the possibility of neutron electric optical devices using not only change of d-spacing but also macroscopic bending of piezoelectric crystal was confirmed. (C) 2004 Elsevier B.V. All rights reserved.
  • JH Kaneko, N Susa, S Tsuchida, M Watanabe, S Miura, T Mizuno, Y Yamauchi, M Hashiba, T Oku, A Homma, F Fujita, T Ino, M Furusaka, T Sawamura, HM Shimizu, Y Kiyanagi
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 529 1-3 307 - 309 2004年08月 [査読有り][通常論文]
     
    A thin GSO scintillator was developed aiming at applications for the neutron science. In order to fabricate a large and thin GSO scintillator in the future, fabrication was started from two types of GSO powders. Although several GSO films were fabricated by evaporation techniques, these films did not have luminescence in photo luminescence (PL) spectroscopy. Thus, these samples were annealed up to 1550degreesC. However, it resulted in no luminescence observation. In response to these results, GSO powders were directly annealed; a phenomenon looking like melting and sintering were observed for Gd2Si2O7:Ce at a temperature higher than 1500degreesC. This sample was quasi-transparent and had luminescence at 405 nm in PL spectrum. In addition, this sample was tougher than a GSO single crystal. In conclusion, the prospect of fabrication of a thin GSO scintillator by combination of annealing and mechanical polishing was obtained. (C) 2004 Elsevier B.V. All rights reserved.
  • M Das, T Sawamura, M Abe, JH Kaneko, A Homma, F Fujita, S Tsuda, T Nishitani
    RADIATION PROTECTION DOSIMETRY 110 1-4 325 - 331 2004年 
    Superheated emulsions being inexpensive, easy to fabricate, and having tissue equivalent composition make them as one of the popular neutron dosemeters. One more advantage is that they can be made insensitive to gamma rays by the choice of the sensitive liquid. It is observed that the response of commercially available bubble detector to neutron decreases above 20 MeV while its response is roughly flat in the 0.1-15 MeV region. This restricts its application as a dosemeter to high-energy neutrons. The response of bubble detector from Bubble Technology Industries, has been observed by using Pb-breeder for high-energy neutrons from different facilities in Japan. It is observed that 2-3 cm Pb-breeder is effective in increasing the response of the detector to the nominal value. Theoretical calculation using MCNPX code indicates an increase in neutrons in the energy range of 0.1-10 MeV with Pb-breeder. The present work indicates the possibility of using the bubble detector as a dosemeter to high-energy neutron using a Pb-breeder of proper thickness.
  • M Kitaichi, S Sawamura, M Wakisaka, JH Kaneko, K Ochiai, T Nishitani, T Sawamura
    RADIATION PROTECTION DOSIMETRY 110 1-4 731 - 738 2004年 [査読有り][通常論文]
     
    In this study spatial and time distribution of neutrons leaking from Hokkaido University 45 MeV Electron Linac facility have measured and compared with the Monte Carlo simulations. The neutron transport processes inside and outside the facility building has been simulated using MCNP. The neutrons have measured by BF3 counters and He-3 counters with polyethylene moderators up to the distance of 330 in from the facility. The spatial distribution of ambient dose equivalent converted from the counts has been compared with the simulation. The distribution estimated from the counts by the BF3 counter has been shown fairly good agreement with the calculation. The spatial distribution of counts obtained at the 45 MeV Electron Linac facility has been compared with that obtained at the Fusion Neutronics Source (FNS) facility of JAERI. The difference between the propagation characteristics of neutrons leaking from those facilities has been discussed.
  • JH Kaneko, T Tanaka, Y Tanimura, A Birumati, Y Hirai, M Katagiri, Y Ikeda, T Nishitani, H Takeuchi, T Iida, T Sawamura
    New Diamond Frontier Carbon Tech 14 5 299 - 311 2004年 [査読有り][通常論文]
     
    The behavior of charge carriers in type-IIa single diamond crystals grown by high-pressure and high-temperature synthesis was observed using nuclear methods. The drift velocities of holes and electrons were measured by a time-of-flight method using a particles from an Am-241 source. Although the drift velocities of holes and electrons were 6.7 x 10(5) cm/s at 30 kV/cm and 6.5 x 10(5) cm/s at 15 kV/cm, respectively, these values are less than 1/10 of the drift velocities of top-grade, high-purity natural-type IIa diamond single crystals reported elsewhere. In addition, pulse-height spectra, i.e., induced-charge distribution, were measured with light illumination to determine the energy levels of trapping centers, and it was revealed that illumination with red light released trapped electrons. Moreover, it was observed that red light illumination facilitated the quick release of trapped holes. To explain these experimental results, the Fermi level and ionizing ratio of impurities were calculated. Results show that nitrogen works as a trapping center for electrons and boron works as a trapping center for holes; probably this center had trapping and detrapping effects on holes. However, it was confirmed that holes could not play the role of a trapping center for electrons. Moreover, it was revealed that another energy level was required for a trapping center for electrons. To explain all experimental results, an energy level 0.6 eV above the valence band was assumed in addition to the nitrogen and boron impurities. In this case, several ppm of acceptor-like centers are required to function as trapping centers for electrons.
  • S Yoshida, T Nishitani, K Ochiai, J Kaneko, J Hori, S Sato, M Yamauchi, R Tanaka, M Nakao, M Wada, M Wakisaka, Murata, I, C Kutsukake, S Tanaka, T Sawamura, A Takahashi
    FUSION ENGINEERING AND DESIGN 69 1-4 637 - 641 2003年09月 [査読有り][通常論文]
     
    The D-T neutron skyshine experiments have been carried out at the Fusion Neutronics Source (FNS) of JAERI with the neutron yield of similar to 1.7 x 10(11) n/s. The concrete thickness of the roof and the wall of a FNS target room are 1.15 and 2 in. respectively. The FNS skyshine port with a size of 0.9 x 0.9 m(2) was open during the experimental period. The radiation dose rate outside the target room was measured a maximum distance of 550 in from the D-T target point with a spherical rem-counter. Secondary gamma-rays were measured with high purity Ge detectors and NaI scintillation counters. The highest neutron dose was about 9 x 10(-22) Sv/(source neutron) at a distance of 30 in from the D-T target point and the dose rate was attenuated to 4 x 10(-24) Sv/(source neutron) at a distance of 550 in. The measured neutron dose distribution was analyzed with Monte Carlo code MCNP-4B and a simple line source model. The MCNP calculation overestimates the neutron dose in the distance range larger than 230 m. The line source model agrees well with the experimental results within the distance of 350 m. (C) 2003 Elsevier Science B.V. All rights reserved.
  • T Sawamura, JH Kaneko, M Abe, M Tamura, Murai, I, A Homma, F Fujita, S Tsuda
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 505 1-2 29 - 32 2003年06月 [査読有り][通常論文]
     
    The response of superheated drop detectors or bubble detectors (BDs) was measured for quasi-monoenergetic neutron beams in the 40-75 MeV range and the effects of a lead-converter enclosing the detector introduced to extend the response to the high-energy region were discussed. The experiments were performed in the quasi-monoenergetic neutron beam field at the AVF cyclotron facility, TAKASAKI Ion Accelerator for Advanced Radiation Application (TIARA) of Japan Atomic Energy Research Institute(JAERI). Monte Carlo calculations by MCNPX code were carried out to estimate the lead-converter effect on neutron spectra in a detector exposed to 40-75 MeV quasi-monoenergetic source neutrons. The calculations indicated an increase in the energy ranges of the neutrons of 0.1-10 MeV and this can be expected to increase the number of bubbles produced in the detector. Experimental results showed that the sensitivity was lowered to about a half the nominal sensitivity and that a 3 cm thick lead-converter could compensate for the sensitivity decrease in the experimental energy region. (C) 2003 Elsevier Science B.V. All rights reserved.
  • JH Kaneko, T Tanaka, T Imai, Y Tanimura, M Katagiri, T Nishitani, H Takeuchi, T Sawamura, T Iida
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 505 1-2 187 - 190 2003年06月 [査読有り][通常論文]
     
    The first investigation of a radiation detector made of a diamond single crystal grown by a chemical vapor deposition (CVD) method was successfully carried out. The diamond single crystal, having a size of 2.0 x 2.0 x 0.7 mm(3), was grown by the CVD method and then applied to the detector. The CVD method was able to reduce nitrogen and boron impurities in diamond crystals more effectively than a high-pressure and high-temperature (HP/HT) method. Consequently the detector had high-energy resolution of 0.4% for 5.486 MeV alpha particles from an Am-241 source. The behavior of charge carriers in the detector could not be adequately investigated because the detector had a partial depression layer and strong rectification. Ionization energy of the CVD diamond was determined to be 16.1 eV; this value was higher than that of the HP/HT type IIa diamond, i.e., 13.1 eV. This result shows the potential of CVD diamond single crystals because an ideal diamond should have higher ionization energy than the HP/HT type IIa diamond that had the influence of impurities. (C) 2003 Elsevier Science B.V. All rights reserved.
  • T Sugie, T Nishitani, S Kasai, J Kaneko, S Yamamoto
    JOURNAL OF NUCLEAR MATERIALS 307 1264 - 1267 2002年12月 [査読有り][通常論文]
     
    The transmissivity of KU-1 quartz which is a candidate of the window material for UV and visible spectroscopy in ITER was measured under the irradiation of 14 MeV neutrons up to the fluence of 7.4 x 10(19) n/m(2) in the UV range (200-400 nm) Significant transmission loss was observed in the wavelength range of 200-300 nm. Two absorption peaks were identified: an E'-center at 215 nm and Si(III) defects at 245 nm. The E'-center absorption is much larger than the Si(III) defect absorption. The transmission loss increased with the neutron fluence, decreased during the irradiation breaks and returned almost to the same level as before when the irradiation resumed. This phenomenon indicates that an absorption induced by the neutron irradiation is caused by stable scattering and short lifetime centers. (C) 2002 Elsevier Science B.V. All rights reserved.
  • R Naka, K Watanabe, J Kawarabayashi, A Uritani, T Iguchi, N Hayashi, N Kojima, T Yoshida, J Kaneko, H Takeuchi, T Kakuta
    IEEE TRANSACTIONS ON NUCLEAR SCIENCE 48 6 2348 - 2351 2001年12月 [査読有り][通常論文]
     
    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 (Sr-90-Y-90), gamma-rays (Cs-137), 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 X 10(-5)% and 1.2 x 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.
  • Y Uno, J Kaneko, T Nishitani, F Maekawa, T Tanaka, S Shibata, Y Ikeda, Khripunov, V, C Walker, K Ebisawa, H Takeuchi
    FUSION ENGINEERING AND DESIGN 56-57 895 - 898 2001年10月 [査読有り][通常論文]
     
    Neutron activation with water flow based on the (16)O(n, p)(16)N reaction (T(1/2) = 7.13 s) has been proposed for the accurate fusion power monitor with reasonable time resolution in International Thermonuclear Experimental Reactor (ITER)-FEAT. The experiment for validation of the method for determining the neutron flux was carried out at the Fusion Neutronics Source (FNS) facility in Japan Atomic Energy Research Institute (JAERI). The stainless steel (SS316)/Water assembly was utilized to simulate a neutron field in the blanket region of ITER. The closed water loop was laid between the assembly and the shielded measurement area. The gamma -rays from the irradiated water were measured by Bi(4)Ge(3)O(12) scintillator which was similar to 12 m away from the irradiation point. The range of the ow velocity was 2-11 m/s. The neutron spectrum at the probe section in the SS316/Water assembly was calculated by the MCNP-4B code with the FENDL/E-2.0 library. The cross section data of the (16)O(n, p)(16)N reaction was taken from the FENDL/A-2.0 file. The counting response of the BGO detector including the effect of the shielding lead blocks surrounding it was calculated by MCNP-4B. The neutron yield from the water activation has a good agreement with that from associated alpha particle detector. (C) 2001 Elsevier Science B.V. All rights reserved.
  • J Kawarabayashi, MR Mardiyanto, A Uritani, T Iguchi, J Kaneko, H Takeuchi
    IEEE TRANSACTIONS ON NUCLEAR SCIENCE 48 3 527 - 529 2001年06月 [査読有り][通常論文]
     
    Numerical analyzes on individual pulses from a cylindrical He-3 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 He-3(n, p)T and He-3(n, n)He-3 at the energy region of the He-3 recoil edge was observed.
  • C Konno, F Maekawa, Y Kasugai, Y Uno, J Kaneko, T Nishitani, M Wada, Y Ikeda, H Takeuchi
    NUCLEAR FUSION 41 3 333 - 337 2001年03月 [査読有り][通常論文]
     
    A series of fusion neutronics experiments has been performed at the Fusion Neutronics Source facility at Japan Atomic Energy Research Institute as ITER EDA R&D tasks to find ways of dealing with various nuclear problems originating from 14 MeV neutrons in ITER. Recently three groups of experiments were carried out: (1) straight duct streaming experiments, (2) decay heat experiments, and (3) development of a fusion power monitor utilizing activation of water. The straight duct streaming experiments suggest that the calculation accuracy for straight duct streaming analyses in ITER nuclear designs is +/-40%. The decay heat experiments show that the accuracy of the decay heat calculation is within 10% for copper and type 316 stainless steel, while it is similar to 30% for tungsten. It is demonstrated that a fusion power monitor utilizing activation of water is applicable to ITER.
  • T Tanaka, J Kaneko, D Takeuchi, H Sumiya, M Katagiri, T Nishitani, H Takeuchi, T Iida, H Ohkushi
    REVIEW OF SCIENTIFIC INSTRUMENTS 72 2 1406 - 1410 2001年02月 [査読有り][通常論文]
     
    Synthetic diamond radiation detectors made of ultrahigh-purity type IIa diamond crystals were developed. The diamond crystals, which were grown by high-pressure and high-temperature synthesis, contained less nitrogen impurity than 0.1 ppm, i.e., 1/10 of conventional type IIa diamond crystals. Since the ultrahigh-purity type IIa diamond crystal was a p-type semiconductor due to a trace impurity of boron, a structure consisting of Schottky and ohmic contacts was adopted for the detectors to suppress an increase in leakage current. For the same purpose, a metal-insulator-semiconductor structure using a chemical vapor deposition diamond insulating layer was adopted for one of the detectors. Plural peaks were observed in the 5.486 MeV alpha energy spectra obtained by the detectors; motion of holes produced the main part of output pulses from the detectors on these measurements. One of the peaks in each spectrum was hardly influenced by light irradiation, even ultraviolet light of 370 nm (3.4 eV), compared with a peak obtained by the conventional type IIa diamond radiation detector. This experimental result indicated that there was a superior part in the crystal where deep energy levels did not exist so much. Although there was no direct evidence, influence of a distribution of the boron impurity in the crystal was expected. On the other hand, electron trapping severely occurred and resulted in loss in charge collection; an effect of the reduction in the nitrogen impurity was not confirmed on the behavior of electrons. (C) 2001 American Institute of Physics.
  • Study on X-Rays and Neutrons Leaked from a 45 MeV Electron Linac Facility
    Sadashi Sawamura, Masatoshi Kitaichi, Ichiro Nojiri, Takuma Yamada, Junichi Kaneko, Teruko Sawamura
    J. Korean Asso. Radiat. Prot 26 3 133 - 137 2001年 [査読有り][通常論文]
  • J Kaneko, Y Uno, T Nishitani, F Maekawa, T Tanaka, Y Shibata, Y Ikeda, H Takeuchi
    REVIEW OF SCIENTIFIC INSTRUMENTS 72 1 809 - 813 2001年01月 [査読有り][通常論文]
     
    As a part of development of nuclear instrumentation for the international thermonuclear experimental reactor (ITER), technical feasibility of a fusion power monitor based on activation of water flow was studied. The fusion power monitor determines D-T neutron yield, i.e., fusion power, by measuring 6.1 and 7.1 MeV gamma rays accompanied by disintegration of N-16 nuclei that are produced by the O-16(n,p) N-16 reactions with 14 MeV neutrons in water. The fusion power monitor consists of a water pipe loop laid from the first wall to the outside of the bioshield and a gamma -ray detector, e.g., a BGO scintillator. Fusion power can be measured in an absolute value by this monitor similar to a neutron activation method with a pneumatic tube system; in addition, this monitor has a feature that continuously measures the fusion power with time resolution faster than 1 s. This monitor also has other excellent features in terms of long-term stability, sensitivity only for D-T neutrons and being maintenance free. In order to confirm the technical feasibility of the fusion power monitor based on activation of water flow, experiments for dependence of N-16 gamma -ray yield on the velocity of water flow and for time response were carried out. It was found that the time response was described in a turbulent flow model, and time resolution of 50 ms that fully satisfied the time resolution of 100 ms required from plasma diagnostics was achieved. Furthermore, detection sensitivity of the fusion power monitor when it is applied to the ITER was estimated based on the experimental results; it was determined that the monitor had sufficiently high sensitivity. (C) 2001 American Institute of Physics.
  • J Kaneko, C Yonezawa, Y Kasugai, H Sumiya, T Nishitani
    DIAMOND AND RELATED MATERIALS 9 12 2019 - 2023 2000年12月 [査読有り][通常論文]
     
    Metallic impurities in high-purity type IIa and conventional type To diamond single crystals grown by high-pressure and high-temperature (HPHT) synthesis were determined by neutron activation analysis using thermal neutrons. Metallic impurities of Fe, Co, Cr and other minor elements were detected in the high-purity type IIa diamond crystal. The typical quantities of these metallic impurities were a few ppb. The influence of these metallic impurities on the electrical properties of the type IIa diamond crystal was practically negligible compared with nitrogen and boron impurities behaving as a donor and an acceptor, respectively. In addition to the impurities detected in the type IIa diamond crystal, Ni impurities of several hundreds of ppb were detected in conventional type Ib diamond crystals. A difference in molten metal solvents used in the synthesis of each diamond crystal resulted in the difference in metallic impurities. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Y Tanimura, J Kaneko, M Katagiri, Y Ikeda, T Nishitani, H Takeuchi, T Iida
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 443 2-3 325 - 330 2000年04月 [査読有り][通常論文]
     
    Characteristics of a synthetic diamond radiation detector in high-temperature environments up to 196 degrees C were investigated. The radiation detector was made of a high-purity type IIa diamond single crystal synthesized by a high-pressure and high-temperature (HP/HT) method. In order to suppress a strong increase in leakage current in a high-temperature environment, a surface barrier structure composed of Schottky and ohmic contacts was adopted. The detector operated as an energy spectrometer for 5.486 MeV alpha particles up to 156 degrees C. The peak due to the alpha particles obtained at 68 degrees C slightly shifted to the higher-energy side compared with the same peak obtained at 25 degrees C; furthermore, the energy resolution of these peaks was improved with the increase in the detector temperature. Effects of trapping and detrapping on holes were suppressed by thermal excitation, and this resulted in an improvement in collection efficiency of charge carriers. With a further increase in the detector temperature, loss of charge carriers became more significant. Finally, operation of the detector was prevented at 196 degrees C by a polarization phenomenon caused by accumulation of space charge in the detector. (C) 2000 Elsevier Science B.V. All rights reserved.
  • K Kimura, J Kaneko, S Sharma, N Itoh
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 154 1-4 318 - 324 1999年06月 [査読有り][通常論文]
     
    Excitation-density dependent luminescence, its decay curves, and time-resolved spectra were measured for ion irradiated alpha-alumina, RbI and CsCl at various temperatures and with a time resolution of 100 ps. Contrary to the usual results of scintillation research, we found that some insulator crystals show excitation-density enhanced stimulated emission through distant interaction between excited states (excitons) and through photons emitted, and found a new 100 ps-lived luminescence band. The manner of excitation-density and temperature dependence of the luminescence efficiency and decay rate of this new band suggests the formation of the exciton complex and further of the electron-hole plasma. (C) 1999 Elsevier Science B.V. All rights reserved.
  • C Mori, J Gotoh, A Uritani, H Miyahara, Y Ikeda, Y Kasugai, J Kaneko, M Sasao, Y Sakuma, K Kudo, N Takeda, T Iida
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 422 1-3 75 - 78 1999年02月 [査読有り][通常論文]
     
    A new type of fast neutron spectrometer composed of a CH4 proportional counter and a Si semiconductor detector which is called the counter telescope type was constructed for plasma-temperature diagnostics. The counting gas CH4 is used as a converter of neutrons to protons. Since the energy loss of the proton in the converter CH4 can be fairly precisely measured with the proportional counter, the energy resolution for the proton is high, so that a good energy resolution for neutrons is obtained. The energy resolution of the spectrometer itself excluding the energy spread of the D-T 14 MeV neutrons was 1.7% which seems to be the best so far, and the detection efficiency was 1 x 10(-6). If better energy resolution is preferable, even 0.5% is obtained and the efficiency in this case is 4 x 10(-8). (C) 1999 Elsevier Science B.V. All rights reserved.
  • J Kaneko, M Katagiri, Y Ikeda, T Nishitani
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 422 1-3 211 - 215 1999年02月 [査読有り][通常論文]
     
    A boron doped CVD diamond contact was applied to a diamond radiation detector for suppressing a polarization phenomenon. A boron doped CVD diamond layer was grown on a synthetic type IIa single crystal diamond; it was then used as a contact. The contact was completely free from radiation damage which is unavoidable in a contact made by an ordinary ion implantation technique. An energy resolution of 0.39% for 5.486 MeV alpha particles was achieved. A steady counting rate higher than 50 cps for alpha particles was confirmed by the developed detector. It is proposed that the boron doped CVD diamond contact functioned as a blocking contact on this detector. (C) 1999 Elsevier Science B.V. All rights reserved.
  • J Kaneko, Y Ikeda, T Nishitani, M Katagiri
    REVIEW OF SCIENTIFIC INSTRUMENTS 70 1 1100 - 1103 1999年01月 [査読有り][通常論文]
     
    The response function of a diamond radiation detector using a synthetic type IIa single diamond crystal for 14 MeV neutrons was measured. There was severe trapping of electrons in the synthetic diamond crystals used in this study. Accordingly, a prototype diamond radiation detector using the synthetic type IIa single diamond whose thickness was 0.1 mm was used with high bias voltage up to 1000 V, i.e., electric field of 100 kV/cm. The measurement resulted in the first observation of a 14 MeV neutron peak corresponding to C-12(n, alpha)Be-9 reactions by a synthetic diamond radiation detector. Energy resolution of the prototype detector for 14 MeV neutrons was 9%. Experimental detection efficiency of the detector was consistent with calculated detection efficiency. Synthetic diamond crystals which do not have trapping of charge carriers are indispensable in order to improve energy resolution for 14 MeV neutrons. (C) 1999 American Institute of Physics. [S0034-6748(99)53301-7].
  • KIMURA K, KANEKO J, SHARMA S, HONG W, ITOH N
    Phys. Rev. B 60 18 12626 - 12634 1999年 [査読有り][通常論文]
  • K Kimura, W Hong, J Kaneko, N Itoh
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 141 1-4 425 - 430 1998年05月 [査読有り][通常論文]
     
    Luminescence spectra and their decay curves are measured for alpha-alumina irradiated by various ions and at various temperatures. The luminescence spectra show several bands in addition to the 3.8-eV band being well-known electron and photon irradiation. The decay curves and time-resolved spectra show enhanced decay of the 3,8-eV band and a new extremely fast decay component at about 400 nm which has a half lifetime of 100 ps or less. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
  • AV Krasilnikov, J Kaneko, M Isobe, F Maekawa, T Nishitani
    REVIEW OF SCIENTIFIC INSTRUMENTS 68 4 1720 - 1724 1997年04月 [査読有り][通常論文]
     
    Two natural diamond detectors (NDDs) operating at room temperature were used for Fusion Neutronics Source (FNS) deuterium-tritium (DT) neutron spectra measurements at different points around the tritium target and for different deuteron beam energies, Energy resolution of both NDDs were measured, with values 1.95% and 2.5%. Due to the higher energy resolution of one of the two NDDs studied it was possible to measure the shape of the DT neutron energy distribution and its broadening due to deuteron scattering inside the target. The influence of pulse pileup on the energy resolution of the combined system (NDD+electronics) at count rates up to 3.8X10(5) counts/s was investigated, A 3.58% energy resolution for the spectrometric system based on NDD and a 0.25 mu s shaping time amplifier has been measured at a count rat of 5.7X10(5) counts/s. It is shown that special development of a fast pulse signal processor is necessary for NDD based spectrometry at count rates of approximately 10(6) counts/s. (C) 1997 American Institute of Physics.
  • M Isobe, T Nishitani, AV Krasilnikov, J Kaneko, M Sasao
    FUSION ENGINEERING AND DESIGN 34-35 573 - 576 1997年03月 [査読有り][通常論文]
     
    A natural diamond detector (NDD) is one of the candidates for the D-T neutron spectrometer in the International Thermonuclear Experimental Reactor since it has a high energy resolution, a high radiation resistance and a very compact size. The characteristic performance of NDD as a D-T neutron spectrometer was examined at the FNS neutron generator. The NDD indicated the energy resolution of 1.95% to 14.1 MeV neutrons. In order to obtain the information of the triton slowing-down, the NDD was applied to the deuterium discharges of the JT-60U tokamak. By accumulating the data of several shots, the change of the pulse height spectrum suggesting the slowing-down of tritons was observed after neutral beam turn-off. (C) 1997 Elsevier Science S.A.
  • T Iguchi, E Takada, M Nakazawa, J Kaneko, T Nishitani, T Matoba, Y Ikeda
    FUSION ENGINEERING AND DESIGN 34-35 585 - 589 1997年03月 [査読有り][通常論文]
     
    A 14 MeV neutron spectrometer suitable for an ITER-like fusion reactor is conceptually designed on the basis of a recoil proton counter telescope method in oblique scattering geometry. To verify the principle and basic performance of the detector concept, preliminary experiments are made for a prototype detector system, where the detector responses are measured to 14 MeV neutrons produced from an accelerator deuterium-tritium (DT) neutron source and compared with the calculated ones. The comparison results show reasonably good agreement and demonstrate the possibility of energy resolution of 2.5% in full width at half maximum for 14 MeV neutron spectrometry. (C) 1997 Elsevier Science S.A.
  • J Kaneko, M Katagiri, Y Ikeda, K Ara, T Iguchi, M Nakazawa
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 385 1 157 - 160 1997年01月 [査読有り][通常論文]
     
    A directional neutron detector based on a recoil proton telescope was investigated by experimental approach. The detector showed a directionality not only for 14-MeV neutrons but also for fission and 2.4-MeV neutrons. Due to a good rise-time pulse-shape discrimination capability of a CsI(Tl) scintillator, a recoil proton energy spectrum was clearly observed in high gamma-ray background. At a detector angle of 21 degrees with respect to the neutron incident direction, the counts corresponding to the high energy neutron became a half of those at 0 degrees. A major source for reducing the signal-to-noise ratio was identified to be the energetic protons via the (n, p) reaction in the CsI(Tl) scintillator.
  • J Kaneko, M Katagiri
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 383 2-3 547 - 548 1996年12月 [査読有り][通常論文]
     
    A diamond radiation detector using a synthetic IIa type mono-crystal was developed. An energy resolution of 0.81%, 45 keV, was achieved for 5.486 MeV alpha particles in a vacuum environment. The ionization energy, epsilon(Diamond), WBS estimated as 13.07 eV by calibration with a silicon surface barrier detector. On a preamplifier output signal, a trapping and detrapping effect on holes was observed.
  • T IGUCHI, J KANEKO, M NAKAZAWA, T MATOBA, T NISHITANI, S YAMAMOTO
    FUSION ENGINEERING AND DESIGN 28 1/4 689 - 698 1995年03月 [査読有り][通常論文]
     
    Neutron measurement in fusion experimental reactors is very important for burning plasma diagnostics and control, monitoring of irradiation effects on device components, neutron source characterization for in-situ engineering tests etc. A conceptual design of neutron diagnostic systems for an International Thermonuclear Experimental Reactor (ITER)-like fusion experimental reactor is made, which consists of a neutron yield monitor, a neutron emission profile monitor and a 14 MeV neutron spectrometer. Each of them is based on a unique idea to meet the required performances for full power conditions assumed at ITER operation. The final design results and expected performances of the promising neutron diagnostic systems are presented together with their critical design issues.
  • 金子 純一
    軽金属 44 1 67 - 68 一般社団法人 軽金属学会 1994年
  • 金子 純一
    繊維学会誌 48 6 P333 - P335 The Society of Fiber Science and Technology, Japan 1992年
  • 金子 純一
    軽金属 40 8 649 - 650 一般社団法人 軽金属学会 1990年
  • 金子 純一
    軽金属 39 3 252 - 253 一般社団法人 軽金属学会 1989年

書籍

  • ダイヤモンドエレクトロニクスの最前線
    シーエムシー出版 2008年
  • Frontier of Diamond for Electronics Applications
    CMC books 2008年
  • 放射線計測
    (担当:共著範囲:第4章第3節第4項、"ダイヤモンド検出器"、p.p. 130-131.)
    国際文献社

その他活動・業績

特許

受賞

  • 2015年03月 北海道大学 教育総長賞・奨励賞
     
    受賞者: 金子純一
  • 2015年03月 北海道大学 研究総長賞 優秀賞
     
    受賞者: 金子純一
  • 2014年03月 北海道大学 研究総長賞
     
    受賞者: 金子純一
  • 2012年03月 日本原子力研究開発機構 先行基礎工学研究協力制度 表彰
     GPS高エネルギー分解能シンチレータによる高信頼性α線波高弁別検出器の開発 
    受賞者: 金子純一
  • 2008年 文部科学省 先進的原子力・エネルギー教育取組、「教育支援活動」優秀賞
     
    受賞者: 住吉 孝、奈良林 直、金子純一

共同研究・競争的資金等の研究課題

  • TlBr中の電荷捕獲準位解明と全吸収γ線エネルギースペクトロメータ開発への挑戦
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 金子 純一, 人見 啓太朗
  • 遮蔽不要な臨界近接監視システム用ダイヤモンド中性子検出器の要素技術開発
    文部科学省:英知を結集した原子力科学技術・人材育成推進事業
    研究期間 : 2020年10月 -2023年03月 
    代表者 : 田中真伸, 金子純一
  • 過酷事故対応電子機器の実用化に向けた耐放射線・高温動作半導体デバイスの高性能化
    文部科学省:原子力システム研究開発事業
    研究期間 : 2020年10月 -2023年03月 
    代表者 : 梅沢仁、金子純一
  • 耐放射線性ダイヤモンド半導体撮像素子の開発
    文部科学省:英知を結集した原子力科学技術・人材育成推進事業
    研究期間 : 2019年10月 -2022年03月 
    代表者 : 大曲 新矢, 金子純一
  • 透明半導体を用いた光子・電子ハイブリッド検出器によるチェレンコフPETの実現
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2019年06月 -2021年03月 
    代表者 : 人見 啓太朗, 錦戸 文彦, 山谷 泰賀, 金子 純一, 小野寺 敏幸, 野上 光博
     
    本研究では陽電子放出断層撮影(positron emission tomography, PET)装置の高度化を実現するガンマ線検出器を開発することを目的としている。本研究ではガンマ線のエネルギー情報と位置情報を電気信号から取得し、時間情報を光信号から取得する光子・電子ハイブリッド検出器の開発を目指している。 当該年度は電気的特性に優れた臭化タリウム(TlBr)と光透過率に優れた塩化タリウム(TlCl)の混晶を育成しガンマ線検出器を製作した。 TlBr素材とTlCl素材を石英管へ封入して溶融することによりTlBr-TlCl混晶素材を得た。良好な電気的特性と光透過率を得るためにTlBr-TlCl混晶素材の純化を帯域精製法を用いて行った。純化後に帯溶融を一回行うことにより結晶育成を行った。実験の結果、光透過率が高いTlBr-TlCl混晶を得ることに成功した。 育成したTlBr-TlCl混晶をダイヤモンドワイヤーソーを用いて切り出し、結晶表面を機械研磨した。結晶の対向する面に、陰極として平板電極を、また、陽極としてガード電極に囲まれたピクセル電極一つを真空蒸着法を用いて形成した。各電極に金線を接続しガンマ線検出器とした。PETで利用される511 keVのガンマ線を放出する22Na放射線源を用いて開発した検出器の評価を室温で行った。製作した検出器は511 keVのガンマ線のピークを明確に検出し、PET用検出器として有望である事が確認できた。 当該年度は光透過率が高いTlBr-TlCl混晶の育成に成功し、良好に動作するTlBr-TlClガンマ線検出器の製作に成功した。これらの成果はPET用の光子・電子ハイブリッド検出器の実現に大きく貢献するものである。
  • 原子炉計装の革新に向けた耐放射線・高温動作ダイヤモンド計測システムの開発とダイヤモンドICの要素技術開発
    文部科学省:原子力システム研究開発事業
    研究期間 : 2016年10月 -2020年03月 
    代表者 : 金子純一
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 田中 真伸, 金子 純一, 小泉 聡, 嶋岡 毅紘
     
    高強度化・高輝度加速器ビームを利用した実験に使用可能な耐環境性能(放射線耐性を含む)・高速応答・高位置分解能を兼ね備えたダイヤモンド半導体測定装置実用化のための技術基盤を確立し、従来の装置性能を大きく向上させることを目的とし研究を行った。 その結果、従来の半導体検出器と同じ性能を持ちつつ耐環境性能に優れたダイヤモンドを用いた半導体測定装置用センサー開発に成功した。更に100μm以下の位置分解能を達成するためのダイヤモンドセンサー製造の知見を蓄積しつつ、ダイヤモンド半導体測定装置用信号処理集積回路用技術開発では、開発したトランジスタが0.3MGy以上の放射線耐性を持つことを確認した。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 山谷 泰賀, 金子 純一, 錦戸 文彦, 中西 貴之
     
    近年、細胞内の遺伝子発現メカニズムや細胞周期といった個々の細胞特性の解明が求められている。本研究では、放射性同位核種をトレーサーとする細胞単位での核医学イメージング装置を開発した。具体的には、β線と150μm厚CsIシンチレータの相互作用で生まれた光をCMOSカメラで撮影した。さらに、CsIよりも密度と発光量が高く、潮解性の無いGPSについても検討した。シミュレーションの結果、シンチレータ厚による半値幅の変化は小さいものの、1/10 幅では厚くなるほど大きく広がり、低出力な成分が増えていくことが分かった。また、10μm厚の GPSであっても全体の9割程度の感度を持つことがわかった。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 金子 純一, 小野田 忍, 坪田 雅功, 田中 真伸, 嶋岡 毅紘, 新名 宏章, 平野 慎太郎, 水越 司
     
    本研究では高速中性子によってダイヤモンド中に生成された空孔と微量な窒素をアニールによってNVセンター化することでアトミックスケールの中性子線量計測の実現可能性を実験的に検証した。試料はCVD法により作製した。照射前と比較し、中性子又は電子線照射後の試料はNVセンターの強い増加を示した。共焦点顕微鏡の測定範囲を超える発光強度だったことから、NVセンターの空間密度を定量化することはできなかった。NVセンターは試料の成長面側に集中して形成されており、合成終了時に窒素の取り込みが多かったことが推定される。線量計測を行うためには窒素が試料全体に均一に取り込まれる必要があるため、合成条件の探索が必要。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 田中 真伸, 金子 純一, 嶋岡 毅紘, 大島 武, 牧野 高紘, 身内 賢太朗
     
    炭素を含むダイヤモンド及び炭化硅素を利用して軽い暗黒物質の検出感度をあげるため、ワイドギャップ半導体ピクセル検出器の研究開発を行った。本研究ではダイヤモンド、炭化硅素を用いた100μmx100μm程度のピクセル検出器を製作しその静特性と電荷収集効率を評価し、充分な信号対雑音比を得る事を確認した。更にワイドギャップ半導体検出器評価用低雑音集積回路を製作し100electronを下回る低雑音性能を達成した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2012年04月 -2016年03月 
    代表者 : 渡邉 雅之, 金子 純一
     
    本研究では、ダイヤモンド表面へ金属イオンが吸着することに着目し、高レベル廃液に含まれている元素のうち主に希土類イオンについて吸着メカニズムの解明を目的とした。酸濃度に対する希土類イオンの吸着分配係数の依存性とその吸着容量、吸着等温線の解析を通して、希土類イオンはダイヤモンドに単層で単純吸着をするとともに、ダイヤモンド表面の吸着サイトに対し1:1の量論比でイオン結合性の吸着することを見出した。 XPS(X線光電子分光)やFT-IR、TRLFS(時間分解型レーザー誘起蛍光分光)などの解析からも上記のメカニズムが妥当であることを示唆する結果が得られた。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2012年04月 -2014年03月 
    代表者 : 金子 純一, 高田 英治
     
    福島第一原子力発電所事故の結果発生した広域汚染により食料に対する安全・安心の確保が必要となった。小売店や直販農家などが自らの販売する食品の放射能を直接測定する安価な検出器の開発を行った。検出器はシンチレータを使用し、食品の自己遮蔽を最大限に活用する事で小型・軽量化を進めた。実験とシミュレーションにより、1.25x1.25x3.0cm3のCsIシンチレータを想定し、5kgの米を測定した場合、スクリーニングレベル50Bq/kgを達成するには22分かかることを明らかとした。また一般家庭での使用を想定した場合、100Bq/kg以下である事を確認するにはより短い時間で判断可能である事も明らかにした。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2010年 -2012年 
    代表者 : 金子 純一, 藤田 文行, 鹿田 真一, 笹尾 真美子, 佐藤 聡, 磯部 光孝, 中井 光男, 浅野 芳裕, 石川 正純
     
    単結晶CVDダイヤモンドの合成条件を最適化した。合成結晶から検出器を製作しα線を使用した誘導電荷量分布測定を行った。その結果、電荷取集効率:100%(正孔)、97%(電子)、μτ積:1×10-4(正孔)、9.6×10-6(電子)cm2/Vを得た。これらの検出器を用い14MeV中性子応答関数測定を行った結果、12C(n,alpha)9Be反応によって生じたピークのエネルギー分解能:3.5%を達成した。また、8GeV電子ビームを使用した時間応答測定では350psの時間分解能を達成した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2008年 -2010年 
    代表者 : 鬼柳 善明, 古坂 道弘, 加美山 隆, 持木 幸一, 平賀 富士夫, 金子 純一, 岩瀬 謙二, 原田 正英, 大井 元喜, 佐藤 節夫, 下ヶ橋 秀典
     
    パルス中性子を用いた透過イメージング法で、中性子透過断面積が金属材料の結晶子配向、結晶子サイズなどの違いによって変化することを明らかにし、それらを定量的に評価できるデータ解析コードを世界に先駆けて開発した。このコードを用いて鉄溶接片における組織構造、結晶子サイズ、さらに引っ張り試験中の鉄版の組織構造、結晶子サイズ、歪イメージの取得に成功した。また、カメラ型検出器のパルス中性子対応化も行なった。
  • CVD単結晶ダイヤモンド合成に基づくDT中性子エネルギースペクトロメータの開発
    日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2008年 -2009年 
    代表者 : 金子 純一, 藤田 文行, 本間 彰
     
    今年度は前年度良い結果の出たリフトオフ法を北海道大学に導入することを第一目標として研究を行った。Ib型基板を使用して連携研究先である産業技術研究所と同一の合成条件でCVD単結晶の合成を行った。合成した試料をリフトオフ法により自立膜化した。さらに化学処理ならびに電極製作を行い、検出器とした。製作した検出器に対してI-V測定、α線応答測定を行った。十分な印加電圧がかかり、α線に対して16%程度ではあるがピークの立つ応答を示す検出器の製作に成功した。今後、高品質基板を使用し、合成条件の最適化を進め実用的な人工ダイヤモンド放射線検出器の実現を目指す。 また合成した結晶中の電荷捕獲準位を同定するための積極的電荷捕獲を利用した光I-V測定法の改良をすすめ、ある程度信頼性のあるデータが取得できる状況に達した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2007年 -2009年 
    代表者 : 久保 直樹, 加藤 千恵次, 金子 純一, 木村 文香, 中丸 洋, 金子 純一
     
    PETは患者さんの生理的情報を定量つまり絶対値として画像に示すことができる.このことで病期の判定,治療方針の決定に対して重要な情報を与える.今回PET画像の作製方法(再構成パラメータ)に関する客観的指標を示すことができ,より定量性を向上させることに貢献できた.また従来,定量画像のために動脈採血をする必要があったがその採血を省略するための装置を試作した.このことでPETをいままでよりも一層患者さんへやさしい検査にできることを示した.
  • 日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2005年 -2009年 
    代表者 : 白土 博樹, 金子 純一, 西山 修輔, 加藤 千恵次, 青山 英史, 関 興一, 鬼丸 力也, 西岡 健, 森田 浩一, 伊達 広行, 高田 英治, 富岡 智, 工藤 與亮, 小野寺 祐也, 神島 保, 鬼丸 力也, 清水 伸一, 作原 祐介, 大山 徳子, 阿保 大介, 田口 大志
     
    2対のシンチレータBGOと位置検出型光電子増倍管とコリメータにて4次元(時空間)定位を可能とするポジトロン・エミッション位置決め装置FPELを開発し、ポジトロンエミッターの量がある値を超えると0.1mmの精度で5mm直径の45MeV電子線ビームの自動的照射が行われる制御が可能な、4次元定位電子線自動照射実験装置を完成した。同装置にて、ヒトの呼吸運動を擬して周期的に動く小動物を利用し、この小動物に植えた腫瘍に対する45MeV電子線ビームの4次元定位放射線治療を行い、金マーカーなしで、腫瘍近傍のポジトロン・エミッターからの信号だけで、腫瘍を制御することに成功し、4次元定位放射線治療の基礎が整った。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2007年 -2008年 
    代表者 : 藤田 文行, 古坂 道弘, 金子 純一, 西山 修輔
     
    定在縞を持つ陽光柱プラズマという秩序状態に、外部から微粒子を導入することでコンプレックスプラズマとする。このプラズマにおける新たな秩序状態(プラズマクリスタル)形成過程を実測し、データ解析を行った。安定な結晶が生成される放電条件で放電させておき、直径10μmの微粒子を落下させると、プラズマ内で微粒子の浮遊が起こり、次いで"気体または液体状態"となり、落下後数十秒以内でプラズマクリスタル状態へ移行していくことを観測した。この新たな秩序の形成過程を評価するために、画像データから対相関関数(動径分布関数)を求めるアルゴリズムを開発した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2006年 -2008年 
    代表者 : 白土 博樹, 本間 さと, 玉木 長良, 久下 裕司, 伊達 広行, 鬼柳 善明, 畠山 昌則, 金子 純一, 水田 正弘, 犬伏 正幸, 但野 茂, 田村 守, 早川 和重, 松永 尚文, 石川 正純, 青山 英史, 作原 祐介, 鬼丸 力也, 阿保 大介, 笈田 将皇, 神島 保, 寺江 聡, 工藤 與亮, 小野寺 祐也, 尾松 徳彦, 清水 伸一, 西村 孝司, 鈴木 隆介, ジェラード ベングア
     
    いままでの先端放射線医療に欠けていた医療機器と患者のinteractionを取り入れた放射線治療を可能にする。臓器の動き・腫瘍の照射による縮小・免疫反応などは、線量と時間に関して非線形であり、システムとしての癌・臓器の反応という概念を加えることが必要であることが示唆された。生体の相互作用を追求していく過程で、動体追跡技術は先端医療のみならず、基礎生命科学でも重要な役割を果たすことがわかった。
  • DT中性子計測への応用をめざしたCVD単結晶ダイヤモンド厚膜の合成と評価
    日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2006年 -2007年 
    代表者 : 金子 純一, 藤田 文行, 本間 彰, 藤森 直治
     
    今年度は人工ダイヤモンド放射線検出器実現を目指し、CVD単結晶ダイヤモンド厚膜の合成と評価を行った。高圧高温合成Ib型基板を使用し、800度・1100度、80Torr・110Torrの4点でダイヤモンドを合成した。合成の主目的はダイヤモンドの{111}面の成長率と{100}面の成長率の比であるα値の把握である。α値によって結晶のモルフォロジーや不純物の取り込みに大きな違いが生じることが知られている。 合成したダイヤモンドのα値は1.6〜4.9に分布した。ラマン分光の結果、全ての試料でダイヤモンドのsp^3結合によるピークが観測された。800度で合成した試料についてはグラファイト成分、窒素と空孔のペアによるNV発光が観測された。また、これら二つの試料については、結晶表面上に平行電極を蒸着により製作し印加電圧をかけた状態でα線を入射させた。この結果、α線により生成した電荷キャリアのドリフトにより信号が出ることを確認した。 さらに、高品質なダイヤモンドの合成を目指し、800度、110Torr、メタン濃度1%での合成をおこなった。その結果、ラマン分光ではグラファイト、NV発光は観測されなかったが、多結晶体的な表面形態をもった結晶であり、α線測定については漏れ電流が大きく信号が出なかった。 今年度の研究の結果、α値3〜4の範囲を集中的にサーベイを行なう必要があるとの結論に至った。次年度以降は低メタン濃度における長時間合成を行なっていく。
  • パルス中性子透過分光撮影法を用いた新しいマテリアルキャラクタリゼーション法の開発
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2005年 -2007年 
    代表者 : 鬼柳 善明, 加美山 隆, 金子 純一, 富岡 智, 竹中 信幸, 古坂 道弘, 猪野 隆
     
    パルス中性子を用いた中性子透過分光法によって得られる画像は、ピクセルごとに中性子断面積の情報を持っているため、これまでの中性子ラジオグラフィーと比べ、対象とするマテリアルの構造情報なども含んだ多くの情報を提供できる。特に、低エネルギー領域に現れるブラッグエッジは結晶構造を反映したものである。その位置のシフトによって歪みの大きさを評価することができる。本研究において屈曲させた鉄試料において、歪みの大きさを定量化できるとともに特定の結晶面で歪みが大きく現れることが明らかに示された。また、ブラッグエッジ付近の断面積の大きさの変化が、結晶粒の大きさと関係することを明らかにし、断面積の大きさと線形関係にあることを示した。さらに、鉄一鉄及びステンレスー鉄の溶接部付近の透過断面積は場所によって変化し、溶接部に近くなるに従って、鋭いブラッグエッジとなることが分った。このことは、結晶面の分布がより等方的になっていることを示唆している。一方、高エネルギー領域では、共鳴吸収を利用した画像が取得でき、元素分布測定や温度測定ができる可能性を示した。検出器素子開発として、Gdベースのシンチレータを用いた検出器を試作し画像を取得した。 このように、パルス中性子透過分光法では、単なる透過画像を取るだけの従来のラジオグラフィーと全く異なった、結晶構造、結晶粒の大きさなどマテリアルのテクスチュアに関係した内部情報を得ることができ、世界的にも注目されている。大型陽子加速器中性子源が稼働をはじめる時期でもあり、これからはより精密な測定が可能になる。この手法の全断面積情報に内包されているものを有効に利用して、より詳細なマテリアルキャラクタリゼーションができるよう、さらなる研究が望まれる。
  • 中性子位相空間変換光学素子の開発
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2005年 -2007年 
    代表者 : 金子 純一, 古坂 道弘, 藤田 文行, 鬼柳 善明, 加美山 隆, 大竹 淑恵
     
    振動する結晶からの中性子回折を二次元中性子検出器と飛行時間法を併用することで、中性子回折角度ならびに強度変化を測定した。 測定では3mm×120mm×14mmのXカット水晶を使用した。水晶はX軸方向に分極を起こすため、この軸に垂直なXカットの変位が最も大きい。結晶上に製作したAl電極に対して40Vの電圧を印加し、22.7kHzの固有振動モードで振動させた。顕微鏡で観察した最大変位量は約5μmであった。 中性子回折実験はJRR-3M、ULSにおいて4.7Åの中性子を使用して行なった。測定器として抵抗分割型光電子増倍管とZnS:Liシンチレータを組み合わせて使用した。結晶を22.7kHz、44μsの周期で振動させて中性子回折像を測定した。その結果、中性子強度分布が時間とともに変化する事を観測した。中性子強度分布は大きく2つの成分からなることが分かった。4.7Åの中性子の速度は約840m/sであり、半周期に当たる22μsで1.8cm進む。検出器を1.8cmもとの1位置からずらした場合、中性子強度変化の位相がπずれることを確認し、回折中性子が結晶の振動周波数と一致した周期性を持つことを確認した。 測定データに対して、二重ガウスフィッティングを行い、ピーク位置ならびに中性子強度変化の時間変化を導いた上で、理論モデルと比較した。ドップラー効果による変位量が変形による変位量より大きい場合、回折中性子強度の時間変化は正弦関数を折り返した形であられる。測定した中性子ピークはこの形になることを確認した。位置の時間変化に関しては、一つのピークに関しては理論計算と概ね一致したが、他方は予測と異なる結果となった。
  • DT中性子計測への応用を目指した高品質単結晶ダイヤモンドの合成と特性評価
    日本学術振興会:科学研究費助成事業 特定領域研究
    研究期間 : 2005年 -2005年 
    代表者 : 金子 純一, 藤田 文行
     
    本研究では二つのテーマについて研究を行った。一つ目のテーマである高品質単結晶ダイヤモンドの合成と評価では、超高純度原料をもちいた高圧高温合成単結晶ダイヤモンドの合成と評価を行い非ダイヤモンド原料を使った場合、結晶性に問題が生じる可能性があること、現状の技術ではHP/HT法によってエネルギースペクトロメータグレードの単結晶ダイヤモンドを造ることはペンディングとすべきであるものの、CVD単結晶合成用の基板としては極めて有望であることを明らかにした。また高品質CVD単結晶ダイヤモンドの合成と評価を行った結果、透明な大面積基板は歩留まりよく合成可能であるものの電気特性向上を狙った合成条件の探求が必要であることがわかった。 二つ目のテーマである電荷捕獲準位同定手法の開発では試料に対する電荷捕獲をあらかじめ行ったうえで、光電流測定を行い、捕獲準位のエネルギー同定を行う測定方法確立の目処を立てた。紫外線とWランプからの単色光を用いた不純物準位の評価技術の開発を行い、超高純度HP/HTダイヤモンド及びCVDダイヤモンドの計測を行った。外気導入による冷却によって試料温度を0℃付近まで下げることで熱雑音を1桁減らし、数100fAの電流計測を可能にした。この方法は従来に無い極めて優れた方法であり、高品質ダイヤモンド合成のために完成を目指すべき手法といえる。
  • 積層構造をもったCVD単結晶ダイヤモンド放射線検出器の開発
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2003年 -2004年 
    代表者 : 金子 純一, 澤村 晃子, 伊藤 利通, 寺地 徳之
     
    本年度は積層型CVDダイヤモンド検出器の製造工程の改良を進めた。前年度、原子レベルで平滑なホウ素ドープ基板上に絶縁層を成長させて検出器を製作することを試みたが、異常成長の影響で満足な性能の検出器を作ることが出来なかった。そこで従来の方法に製作方法を戻して検出器の性能改善を試みた。その過程で積層したCVDダイヤモンド層がIb型基板結晶の表面状態の影響を大きく受けていることが分かった。そこで結晶研磨方法と成長するダイヤモンド層の相関関係に関する検討を行った。以前はダイヤモンドの異方性によって、比較的削りやすい方向に削られた基板上にダイヤモンドを成長させていたため、比較的結晶性の良いCVD単結晶が得られていたが、研磨メーカーがランダムな方向に結晶を研磨する手法に変更を行った結果、全く質の悪いCVDダイヤモンド層しかえられなくなっていることが分かった。そこで、研磨方法をより優れた方法に変更することによってこの問題を解決した。またあらたな構造としてわずかなホウ素不純物のみを含んだIIb型基板の上にCVD単結晶を成長して検出器として動作させることも試みた。また製作した検出器の特性評価を行う目的で整備した213nmUVパルスレーザーとα線をもちいた電荷キャリアの輸送特性評価システムを完成し、製作した検出器の特性評価を行った。評価では積層型CVDダイヤモンド放射線検出器のほかCVDダイヤモンド自立膜や高純度高圧高温合成単結晶の評価を行った。また検出器評価の一環として14MeV中性子に対する応答関数測定実験を行なった。
  • 新材料メタンハイドレートを用いた高性能パルス中性子減速材の開発
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2002年 -2004年 
    代表者 : 鬼柳 善明, 加美山 隆, 平賀 富士夫, 澤村 晃子, 金子 純一, 古坂 道弘
     
    メタンハイドレートの中性子断面積の特性を知るために、中性子非弾性散乱実験を行い、そのデータ解析を進めた。メタン分子の回転は自由回転に近く、最低レベルを1.1meVとして自由回転モデルで計算することによって、上手く実験でのエネルギーレベルが再現できる。しかし、これだけでは散乱強度を全て説明できなかった。この原因としてメタンの氷格子中での並進運動が考えられ、4.4meVと7.4meVに大ケージと小ケージに対応すると思われるピークがあることが分かった。これらのピークは実験的に初めて明らかにされたものである。水分子の揺動運動については、メタンハイドレートと氷で、強度分布に少し差がみられた。しかし、全体としては、メタンハイドレートの断面積は、メタン単体の断面積と氷の断面積を足し合わせることによって近似出来ることが分かった。 メタンハイドレートの中性子エネルギースペクトルと放出時間分布の測定を、結合型と非結合型の減速材タイプについて行った。結合型減速材においてはスペクトルの形は、氷のものに近かった。ピークエネルギーは、メタンや水素が約3meVであるのに対して、約7meVと高くなっていた。そのため、熱中性子領域では強度が高いが、冷中性子領域ではかなり低くなっている。非結合型減速材においても、同様の結果が得られ、水素減速材やメタン減速材よりも特性は劣っていた。また、中性子放出時間は、他の減速材より広い分布を示しており、この観点からも劣ることが示された。この結果から、メタンハイドレートは、熱中性子から冷中性子までの広いエネルギー領域でスペクトル強度があまり変化しないという特徴を持つが、冷中性子領域では、強度がメタンや水素より劣る。これは、減速が良いメタンの効果があまり大きくなく、氷の特徴が主として表れたためと考えられる。この減速材を冷中性子源として使用するメリットはあまりないと考えられる。
  • 医用原子力
    研究期間 : 2004年
  • Nuclear engineering for radiation therapy and diagnostics
    研究期間 : 2004年
  • 中性子散乱実験用高速・高位置分解能二次元中性子検出器開発のための基礎研究
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2002年 -2003年 
    代表者 : 金子 純一, 片桐 政樹
     
    今年度は前年度行なったGd金属箔の検出効率が思うように上がらなかったことから、Gd系シンチレータの薄膜化とMCPの組み合わせについて実験的に研究を進めた。Gd金属箔からの内部転換電子は1方向へのみ放出された分がMCPに入射可能となる。一方、Gd系シンチレータを使用した場合は、内部転換電子がシンチレータ内で光に変換されるため、光の取り出しを上手く行なうことで4π方向に出た内部転換電子を全て捉えることができる。この方法をもちいた場合、最大の問題となるのがMCPが直接γ線や中性子線と反応することである。この部分については北大ライナックならびに高エネルギー加速器研究機構KENSにおける実験を行い、MCPが直接反応した場合の信号の減衰時間(数ns)とシンチレータの減衰時間(数10ns)程度の違いをもちいて弁別できることを確認した。またシンチレータの薄膜化については、今後さらに進める必要があるものの、焼結手法によって中性子をほぼ100%捕獲し、γ線の影響を最低限に抑えられる30μmの厚さを得るめどを立てた。このシンチレータは焼結条件によって発光強度と透明度が変わることが分かっている。この部分については今後、合成条件の最適化をすすめる必要がある。本研究は今年度で終了するが、Gd系シンチレータとMCPを組み合わせることで、中性子イメージングを行なえる基礎的実証データを積み上げることに成功し、初期の目的を達成することが出来た。今後、さらに100μm以下の位置分解能をもち、残留応力測定等に使える中性子イメージング装置の開発につなげていく必要がある。
  • 酸化物シンチレータの開発
    研究期間 : 2001年
  • development of oxide scintillators
    研究期間 : 2001年
  • 中性子散乱実験用中性子検出器・中性子光学素子の開発
    研究期間 : 1999年
  • Development of neutron detectors and neutron optics
    研究期間 : 1999年
  • 人工ダイヤモンド放射線検出器の開発
    研究期間 : 1994年
  • Development of synthetic diamond radiation detectors
    研究期間 : 1994年

教育活動情報

主要な担当授業

  • 量子ビーム計測工学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 放射線計測、統計、ガス検出器、シンチレーション検出器、半導体検出器、スペクトル測定、中性子計測
  • 大学院共通授業科目(一般科目):人文社会科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 経営戦略、マーケティング、外部環境の機会・脅威の認識、組織の強み・弱みの把握、企業の市場戦略
  • 大学院共通授業科目(一般科目):人文社会科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : PBL、企業課題、新規事業
  • 大学院共通授業科目(一般科目):人文社会科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : ビジネスシミュレーション、経営戦略、財務、マーケティング、損益分岐点計算、戦略的意思決定
  • 大学院共通授業科目(一般科目):人文社会科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : アカウンティング、ファイナンス、財務諸表、財務諸表分析、キャッシュフロー、時間価値
  • 量子ビーム計測工学特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : 放射線計測、統計、ガス検出器、シンチレーション検出器、半導体検出器、スペクトル測定、中性子計測
  • 原子物理
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 原子、原子核、核反応、放射線、物質との相互作用、放射線防護
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : PBL、企業課題、新規事業
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : プログラミング、スマートフォン、アプリケーション
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : プログラミング、デザイン思考、ハッカソン
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : ビジネスシミュレーション、経営戦略、財務、マーケティング、損益分岐点計算、戦略的意思決定
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 量子ビーム、プラズマ、触媒、ナノ材料

大学運営

学内役職歴

  • 2020年10月12日 - 2021年3月31日 経営戦略室室員
  • 2017年4月1日 - 2019年3月31日 研究戦略室室員
  • 2019年4月1日 - 2020年9月30日 研究戦略室室員
  • 2020年10月12日 - 2022年3月31日 研究戦略室室員
  • 2017年4月1日 - 2023年3月31日 産学・地域協働推進機構副機構長
  • 2017年4月1日 - 2019年3月31日 総長補佐
  • 2019年4月1日 - 2020年9月30日 総長補佐
  • 2020年10月12日 - 2022年3月31日 総長補佐

委員歴

  • 2010年   日本原子力学会   標準委員会 原子燃料サイクル専門部会 臨界安全管理分科会 委員   日本原子力学会


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