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Toyoda, Shin*; Inoue, Kazuhiko*; Yamaguchi, Ichiro*; Hoshi, Masaharu*; Hirota, Seiko*; Oka, Toshitaka; Shimazaki, Tatsuya*; Mizuno, Hideyuki*; Tani, Atsushi*; Yasuda, Hiroshi*; et al.
Radiation Protection Dosimetry, 199(14), p.1557 - 1564, 2023/09
Times Cited Count：0 Percentile：0.01(Environmental Sciences)Interlaboratory comparison studies are important for radiation dosimetry in order to demonstrate how the technique is universally available. The set of standard samples are examined in each participating laboratory in the present study. After a set of standard samples together with the samples with unknown doses, which were prepared in the same laboratory as the standard samples, are measured at a participating laboratory, those samples are sent to another participating laboratory for next measurement. There is some small difference observed in the sensitivity (the slope of the dose response line) of the standard samples while the differences in the obtained doses for the samples with unknown doses are rather systematic, implying that the difference is mostly due to the samples but not to measurements.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
TEM observation and MD simulation of frank partial dislocation climbing in Al-Cu alloyChen, J.*; Yoshida, Kenta*; Suzudo, Tomoaki; Shimada, Yusuke*; Inoue, Koji*; Konno, Toyohiko*; Nagai, Yasuyoshi*
Materials Transactions, 63(4), p.468 - 474, 2022/04
Times Cited Count：1 Percentile：15.81(Materials Science, Multidisciplinary)In situ electron irradiation using high-resolution transmission electron microscopy (HRTEM) was performed to visualize the Frank loop evolution in aluminium-copper (Al-Cu) alloy with an atomic-scale spatial resolution of 0.12 nm. The 
HRTEM observation along the [110] direction of the FCC-Al lattice, Frank partial dislocation bounding an intrinsic stacking fault exhibited an asymmetrical climb along the 
112
direction opposed to those in the reference pure Al under an electron irradiation, with a corresponding displacement-per-atom rate of 0.055-0.120 dpa/s. The asymmetrical climb of the partial dislocation was described as pinning effects due to Cu-Cu bonding in Guinier-Preston zones by a molecular dynamics simulation.
Ono, Shinya*; Inoue, Kei*; Morimoto, Masahiro*; Arae, Sadanori*; Toyoshima, Hiroaki*; Yoshigoe, Akitaka; Teraoka, Yuden; Ogata, Shoichi*; Yasuda, Tetsuji*; Tanaka, Masatoshi*
Surface Science, 606(21-22), p.1685 - 1692, 2012/11
Times Cited Count：8 Percentile：35.26(Chemistry, Physical)Hanada, Masaya; Kojima, Atsushi; Tanaka, Yutaka; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Tobari, Hiroyuki; Umeda, Naotaka; Akino, Noboru; et al.
Fusion Engineering and Design, 86(6-8), p.835 - 838, 2011/10
Times Cited Count：13 Percentile：69.55(Nuclear Science & Technology)Neutral beam (NB) injectors for JT-60 Super Advanced (JT-60SA) have been designed and developed. Twelve positive-ion-based and one negative-ion-based NB injectors are allocated to inject 30 MW D
beams in total for 100 s. Each of the positive-ion-based NB injector is designed to inject 1.7 MW for 100s at 85 keV. A part of the power supplies and magnetic shield utilized on JT-60U are upgraded and reused on JT-60SA. To realize the negative-ion-based NB injector for JT-60SA where the injection of 500 keV, 10 MW D beams for 100s is required, R&Ds of the negative ion source have been carried out. High-energy negative ion beams of 490-500 keV have been successfully produced at a beam current of 1-2.8 A through 20% of the total ion extraction area, by improving voltage holding capability of the ion source. This is the first demonstration of a high-current negative ion acceleration of 1 A to 500 keV. The design of the power supplies and the beamline is also in progress. The procurement of the acceleration power supply starts in 2010.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.
AIP Conference Proceedings 1390, p.466 - 475, 2011/09
Times Cited Count：2 Percentile：53.22(Physics, Atomic, Molecular & Chemical)Voltage holding tests by using JT-60 negative ion source and small electrodes was carried out because JT-60 negative ion source had a critical problem about low voltage holding capability for long time. As a result, the voltage holding capability is decreased with the increase of area where local electric field is generated, as well as the surface area according to existing scaling low about surface area. Therefore, in order to improve the voltage holding without changing the existing accelerator, the voltage holding test was carried out by extending gap lengths of the negative ion source. In order to improve the voltage holding, beam radiation shield needs to be optimized additionally. As a result, the voltage holding has been improved to 500 kV and stabilized. By using this modified ion source, negative ion beams of 500 keV up to 3A has been successfully produced.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08
Times Cited Count：51 Percentile：88.28(Physics, Fluids & Plasmas)Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m
for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.
Ono, Shinya*; Inoue, Kei*; Morimoto, Masahiro*; Arae, Sadanori*; Toyoshima, Hiroaki*; Yoshigoe, Akitaka; Teraoka, Yuden; Ogata, Shoichi*; Yasuda, Tetsuji*; Tanaka, Masatoshi*
Shingaku Giho, 111(114), p.23 - 27, 2011/07
The initial oxidation on high-index silicon surfaces with (113) and (120) orientations at 820 K has been investigated by real-time X-ray photoemission spectroscopy (Si 2p and O 1s) using 687 eV photons. The time evolutions of the Si
(n=1-4) components in the Si 2p spectrum indicate that the Si
state is suppressed on high-index surfaces compared with Si(001). The O 1s state consists of two components, a low-binding-energy component (LBC) and a high-binding-energy component (HBC). It is suggested that the O atom in strained Si-O-Si contributes to the LBC component. The reaction rates are slower on high-index surfaces compared with that on Si(001).
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 
2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.
Kashiwagi, Mieko; Taniguchi, Masaki; Kojima, Atsushi; Dairaku, Masayuki; Hanada, Masaya; Hemsworth, R. S.*; Mizuno, Takatoshi*; Takemoto, Jumpei; Tanaka, Masanobu*; Tanaka, Yutaka*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
At JAEA, a multi-aperture multi-grid accelerator has been developed for the ITER neutral beam system. A target is H
ion beam acceleration of 0.5 A (200 A/m) at 1 MeV. In real accelerators, it was found that the voltage holding was about a half of that obtained in an ideal small electrode. After applying necessary gap length and radii of edges of grid supports to lower local electric field concentrations, the accelerator succeeded in sustaining 1 MV for 4000 s. As a result, beam parameters were increased to 879 keV, 0.36 A (157 A/m) at perveance matched condition from 796 kV, 0.32 A (140 A/m) reported in FEC2008. In the beam acceleration, the beamlet deflections due to magnetic field and space charge repulsion caused direct interceptions, that resulted in limitations in the beam energy and current. Compensation of these beamlet deflections has been tested applying aperture offset and field shaping plate, which were examined in a three-dimensional beam analysis.
Hanada, Masaya; Akino, Noboru; Endo, Yasuei; Inoue, Takashi; Kawai, Mikito; Kazawa, Minoru; Kikuchi, Katsumi; Komata, Masao; Kojima, Atsushi; Mogaki, Kazuhiko; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.208 - 213, 2010/08
A large negative ion source with an ion extraction area of 110 cm 
45 cm has been developed to produce 500 keV, 22 A D ion beams required for JT-60 Super Advanced. To realize the JT-60SA negative ion source, the JT-60 negative ion source has been modified and tested on the negative-ion-based neutral beam injector on JT-60U. A 500 keV H ion beam has been produced at 3 A without a significant degradation of beam optics. This is the first demonstration of a high energy negative ion acceleration of more than one-ampere to 500 keV in the world. The beam current density of 90 A/m is being increased to meet 130 A/m of the design value for JT-60SA by tuning the operation parameters. A long pulse injection of 30 s has been achieved at a injection D power of 3 MW. The injection energy, defined as the product of the injection time and power, reaches 80 MJ by neutralizing a 340 keV, 27 A D ion beam produced with two negative ion sources.
ion beam acceleration in MeV acceleratorTaniguchi, Masaki; Mizuno, Takatoshi; Umeda, Naotaka; Kashiwagi, Mieko; Watanabe, Kazuhiro; Tobari, Hiroyuki; Kojima, Atsushi; Tanaka, Yutaka; Dairaku, Masayuki; Hanada, Masaya; et al.
Review of Scientific Instruments, 81(2), p.02B101_1 - 02B101_3, 2010/02
Times Cited Count：7 Percentile：34.64(Instruments & Instrumentation)A Multi-Aperture Multi-Grid (MAMuG) accelerator called "MeV accelerator" has been developed for neutral beam injection (NBI) system of ITER. The MeV accelerator succeeded in accelerating 796 keV, 320 mA H ion beam until 2007. However, pulse length was limited to 0.2 s due to un-cooled grids. In the present work, long pulse H ion beam acceleration was performed by the MeV accelerator equipped with water-cooled new grids. The H ion current was increased step by step at certain energy with seeding Cs up to the optimum perveance. At present, pulse length was extended to 5 s for 750 keV, 221 mA (perveance match) and maximum power of 1.01 MJ was achieved (650 keV, 163 mA, 10s). At higher energy and current, pulse length was limited by breakdowns between the grids. This was due to high heat load on A3G and GRG grid by deflection of H ion beam.
Tanaka, Yutaka; Hanada, Masaya; Kojima, Atsushi; Akino, Noboru; Shimizu, Tatsuo; Oshima, Katsumi; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; et al.
Review of Scientific Instruments, 81(2), p.02A719_1 - 02A719_3, 2010/02
Times Cited Count：4 Percentile：22.78(Instruments & Instrumentation)The JT-60U negative ion source is required to produce 44 A of 500 keV D ion beams for the JT-60SA. So far, acceleration voltage of 450 kV was achieved without beam acceleration and 416 kV with beam acceleration. These are lower than the rated voltage for JT-60SA due to vacuum breakdowns. To examine the cause of vacuum breakdown, the complicated structure of the accelerator was modeled for the calculation of electric field inside the accelerator. At the corners of the grid support flanges, the electric fields are locally concentrated to be 5.2-5.5 kV/mm. This is higher than other parts of the accelerator where the averaged field is around 3 kV/mm. To reduce the concentrated electric field, the support structures were modified to extend the gap lengths between grids. By repeating the high-voltage application of 3 s pulses, the applied voltage was increased. After 15 hours of conditioning, the accelerator sustained its rated value of 500 kV without beam acceleration.
Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Grisham, L. R.*; et al.
Review of Scientific Instruments, 81(2), p.02B112_1 - 02B112_5, 2010/02
Times Cited Count：35 Percentile：78.63(Instruments & Instrumentation)The negative-ion based NB injectors on JT-60U achieved maximum injection power of 5.8 MW for 0.9 s via a neutralization of 400 keV, 35 A D ion beams produced in two ion sources. Furthermore, D beams of 3.4 MW were injected for 20 s using two negative ion sources. The pulse length was limited by power load on the acceleration grids. Reducing the grid power load to an allowable level, long pulse injections was achieved for 30 s at 3 MW. For JT-60SA, 500 keV, 22 A, 100 s beams are required. However, the achieved highest beam energy has been limited to 415 keV. To improve the voltage holding capability, the gap extension and the optimization of the structures have been designed in order to mitigate the local electric field. As a result, the voltage holding capability of 500 kV has been demonstrated. Furthermore, 490 kV for 40 s has been sustained without breakdown. The demonstration of the 500 keV beam acceleration is planned in September 2009 using the modified ion source.
Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.
IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08
Times Cited Count：12 Percentile：43.9(Physics, Fluids & Plasmas)The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.
Ikeda, Yoshitaka; Akino, Noboru; Ebisawa, Noboru; Hanada, Masaya; Inoue, Takashi; Honda, Atsushi; Kamada, Masaki; Kawai, Mikito; Kazawa, Minoru; Kikuchi, Katsumi; et al.
Fusion Engineering and Design, 82(5-14), p.791 - 797, 2007/10
Times Cited Count：22 Percentile：80.6(Nuclear Science & Technology)Modification of JT-60U to a superconducting device (so called JT-60SA) has been planned to contribute to ITER and DEMO. The NBI system is required to inject 34 MW for 100 s. The upgraded NBI system consists of twelve positive ion based NBI (P-NBI) units and one negative ion based NBI (N-NBI) unit. The injection power of the P-NBI units are 2 MW each at 85 keV, and the N-NBI unit will be 10 MW at 500 keV, respectively. On JT-60U, the long pulse operation of 30 s at 2 MW (85 keV) and 20 s at 3.2 MW (320 keV) have been achieved on P-NBI and N-NBI units, respectively. Since the temperature increase of the cooling water in both ion sources is saturated within 20 s, further pulse extension up to 100 s is expected to mainly modify the power supply systems in addition to modification of the N-NBI ion source for high acceleration voltage. The detailed technical design of the NBI system for JT-60SA is presented.
Ikeda, Yoshitaka; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hanada, Masaya; Honda, Atsushi; Inoue, Takashi; Kawai, Mikito; Kazawa, Minoru; et al.
Nuclear Fusion, 46(6), p.S211 - S219, 2006/06
Times Cited Count：59 Percentile：87.12(Physics, Fluids & Plasmas)Recently, the extension of the pulse duration up to 30 sec has been intended to study quasi-steady state plasma on JT-60U N-NBI system. The most serious issue is to reduce the heat load on the grids for long pulse operation. Two modifications have been proposed to reduce the heat load. One is to suppress the beam spread which may be caused by beamlet-beamlet interaction in the multi-aperture grid due to the space charge force. Thin plates were attached on the extraction grid to modify the local electric field. The plate thickness was optimized to steer the beamlet deflection. The other is to reduce the stripping loss, where the electron of the negative ion beam is stripped and accelerated in the ion source and then collides with the grids. The ion source was modified to reduce the pressure in the accelerator column to suppress the beam-ion stripping loss. Up to now, long pulse injection of 17 sec for 1.6 MW and 25 sec for 1 MW has been obtained by one ion source with these modifications.
Kawai, Mikito; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hanada, Masaya; Honda, Atsushi; Inoue, Takashi; Kazawa, Minoru; Kikuchi, Katsumi*; Kuriyama, Masaaki; et al.
Fusion Science and Technology, 44(2), p.508 - 512, 2003/09
Times Cited Count：5 Percentile：36.77(Nuclear Science & Technology)The negative ion source for negative ion based neutral beam injector(N-NBI) of JT-60U aims at generating a negative ion beam with 500 keV and 22A for 10s. The N-NBI system was completed in 1996, followed by starting the efforts to increase beam power and energy. (1)Spatial non-uniformity of the source plasma causes position-dependent divergence of a beamlet due to mis-matching of local beam perveance. A part of the divergent energetic beams is intercepted by the grids and resultantly produce the excessive heat load of the grids and/or induce the high voltage breakdown. So several techniques to take measures against and to correct the non-uniformity in these sources were implemented. (2)Correction of beamlet deflection by adjusting the electric field at the extraction grids. It improved the beam divergence and then decreased an excessive heat load of a beam limiter by more than 50 %. As a result, the maximum injection power 6.2MW and beam pulse duration 10 seconds were obtaind.
Oikawa, Masakazu*; Kamiya, Tomihiro; Fukuda, Mitsuhiro; Okumura, Susumu; Inoue, Hiromitsu*; Masuno, Shinichi*; Umemiya, Shinsuke*; Oshiyama, Yoshifumi*; Taira, Yutaka*
Nuclear Instruments and Methods in Physics Research B, 210(1-4), p.54 - 58, 2003/09
Times Cited Count：25 Percentile：82.86(Instruments & Instrumentation)no abstracts in English
Morishita, Masaki; Aoto, Kazumi; Kasahara, Naoto; Asayama, Tai; Sagayama, Yutaka*; Inoue, Kazuhiko*; Shibamoto, Hiroshi*; Tanaka, Yoshihiko*
JNC TY9400 2003-001, 644 Pages, 2003/05
JNC-TY9400-2003-001.pdf:22.68MB
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