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Moriguchi, Yuichi*; Sato, Yosuke*; Morino, Yu*; Goto, Daisuke*; Sekiyama, Tsuyoshi*; Terada, Hiroaki; Takigawa, Masayuki*; Tsuruta, Haruo*; Yamazawa, Hiromi*
KEK Proceedings 2021-2, p.21 - 27, 2021/12
no abstracts in English
(001) surface using supersonic seeded oxygen molecular beamKatsube, Daiki*; Ono, Shinya*; Takayanagi, Shuhei*; Ojima, Shoki*; Maeda, Motoyasu*; Origuchi, Naoki*; Ogawa, Arata*; Ikeda, Natsuki*; Aoyagi, Yoshihide*; Kabutoya, Yuito*; et al.
Langmuir, 37(42), p.12313 - 12317, 2021/10
Times Cited Count：1 Percentile：6.77(Chemistry, Multidisciplinary)We investigated the oxidation of oxygen vacancies at the surface of anatase TiO(001) using supersonic seeded molecular beam (SSMB) of oxygen. The oxygen vacancies at the top-surface and sub-surface could be eliminated by the supply of oxygen using an SSMB. These results indicate that the interstitial vacancies can be mostly assigned to oxygen vacancies, which can be effectively eliminated by using an oxygen SSMB. Oxygen vacancies are present on the surface of anatase TiO(001) when it is untreated before transfer to a vacuum chamber. These vacancies, which are stable in the as-grown condition, could also be effectively eliminated using the oxygen SSMB.
Si single crystal grown by the flux methodTakeuchi, Tetsuya*; Haga, Yoshinori; Taniguchi, Toshifumi*; Iha, Wataru*; Ashitomi, Yosuke*; Yara, Tomoyuki*; Kida, Takanori*; Tahara, Taimu*; Hagiwara, Masayuki*; Nakashima, Miho*; et al.
Journal of the Physical Society of Japan, 89(3), p.034705_1 - 034705_15, 2020/03
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)
Cs plumes from the Fukushima Daiichi Nuclear Power Plant; Evaluation of the model intercomparison data of the Science Council of JapanKitayama, Kyo*; Morino, Yu*; Takigawa, Masayuki*; Nakajima, Teruyuki*; Hayami, Hiroshi*; Nagai, Haruyasu; Terada, Hiroaki; Saito, Kazuo*; Shimbori, Toshiki*; Kajino, Mizuo*; et al.
Journal of Geophysical Research; Atmospheres, 123(14), p.7754 - 7770, 2018/07
Times Cited Count：24 Percentile：69.81(Meteorology & Atmospheric Sciences)We compared seven atmospheric transport model results for Cs released during the Fukushima Daiichi Nuclear Power Plant accident. All the results had been submitted for a model intercomparison project of the Science Council of Japan in 2014. We assessed model performance by comparing model results with observed hourly atmospheric concentrations of Cs, focusing on nine plumes over the Tohoku and Kanto regions. The results showed that model performance for Cs concentrations was highly variable among models and plumes. We also assessed model performance for accumulated Cs deposition. Simulated areas of high deposition were consistent with the plume pathways, though the models that best simulated Cs concentrations were different from those that best simulated deposition. The ensemble mean of all models consistently reproduced Cs concentrations and deposition well, suggesting that use of a multimodel ensemble results in more effective and consistent model performance.
Theis, C.*; Carbonez, P.*; Feldbaumer, E.*; Forkel-Wirth, D.*; Jaegerhofer, L.*; Pangallo, M.*; Perrin, D.*; Urscheler, C.*; Roesler, S.*; Vincke, H.*; et al.
EPJ Web of Conferences, 153, p.08018_1 - 08018_5, 2017/09
Times Cited Count：0 Percentile：0.03(Nuclear Science & Technology)At CERN, gas-filled ionization chambers PTW-34031 (PMI) are commonly used in radiation fields including neutrons, protons and 
-rays. A response function for each particle is calculated by the radiation transport code FLUKA. To validate a response function to high energy neutrons, benchmark experiments with quasi mono-energetic neutrons have been carried out at RCNP, Osaka University. For neutron irradiation with energies below 200 MeV, very good agreement was found comparing the FLUKA simulations and the measurements. In addition it was found that at proton energies of 250 and 392 MeV, results calculated with neutron sources underestimate the experimental data due to a non-negligible gamma component originating from the target 
Li(p,n)Be reaction.
Takahashi, Yoshikazu; Suwa, Tomone; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; et al.
IEEE Transactions on Applied Superconductivity, 25(3), p.4200904_1 - 4200904_4, 2015/06
Times Cited Count：3 Percentile：20.23(Engineering, Electrical & Electronic)The Japan Atomic Energy Agency (JAEA) is responsible for procuring all amounts of Central Solenoid (CS) Conductors for ITER, including CS jacket sections. The conductor is cable-in-conduit conductor (CICC) with a central spiral. A total of 576 Nb
Sn strands and 288 copper strands are cabled around the central spiral. The maximum operating current is 40 kA at magnetic field of 13 T. CS jacket section is circular in square type tube made of JK2LB, which is high manganese stainless steel with boron added. Unit length of jacket sections is 7 m and 6,300 sections will be manufactured and inspected. Outer/inner dimension and weight are 51.3/35.3 mm and around 90 kg, respectively. Eddy Current Test (ECT) and Phased Array Ultrasonic Test (PAUT) were developed for non-destructive examination. The defects on inner and outer surfaces can be detected by ECT. The defects inside jacket section can be detected by PAUT. These technology and the inspected results are reported in this paper.
Sn cable assembled with conduit for ITER central solenoidNabara, Yoshihiro; Suwa, Tomone; Takahashi, Yoshikazu; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Sakurai, Takeru; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; et al.
IEEE Transactions on Applied Superconductivity, 25(3), p.4200305_1 - 4200305_5, 2015/06
Times Cited Count：0 Percentile：0(Engineering, Electrical & Electronic)
Sn conductors for toroidal field coils in ITERNabara, Yoshihiro; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Suwa, Tomone; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Koizumi, Norikiyo; et al.
IEEE Transactions on Applied Superconductivity, 24(3), p.6000605_1 - 6000605_5, 2014/06
Times Cited Count：7 Percentile：39.51(Engineering, Electrical & Electronic)no abstracts in English
ion beams for ITER NB acceleratorUmeda, Naotaka; Kashiwagi, Mieko; Taniguchi, Masaki; Tobari, Hiroyuki; Watanabe, Kazuhiro; Dairaku, Masayuki; Yamanaka, Haruhiko; Inoue, Takashi; Kojima, Atsushi; Hanada, Masaya
Review of Scientific Instruments, 85(2), p.02B304_1 - 02B304_3, 2014/02
Times Cited Count：12 Percentile：48.5(Instruments & Instrumentation)In order to realize neutral beam systems in ITER whose target is to produce D ion beam of 1 MeV, 200 A/m
during 3600s, the electrostatic five-stages negative ion accelerator has been developed at JAEA. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic filter in the accelerator was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The use of new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m, 881 keV H ion beam has been successfully extended from a previous value of 0.4s to 8.7s.
Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Kojima, Atsushi; Yoshida, Masafumi; Taniguchi, Masaki; Dairaku, Masayuki; Maejima, Tetsuya; Yamanaka, Haruhiko; Watanabe, Kazuhiro; et al.
Review of Scientific Instruments, 85(2), p.02B320_1 - 02B320_3, 2014/02
Times Cited Count：29 Percentile：75.28(Instruments & Instrumentation)The negative ion extractor for high power and long-pulse operations is newly developed toward the neutral beam injector (NBI) for heating & current drive of future fusion machines such as ITER, JT-60 Super Advanced (SA) and DEMO reactor. The satisfactory cooling capability is designed in the thermal analysis. A negative ion production and a suppression of electrons are experimentally validated for this new extractor. As the results, the negative ion current shows increases by a factor of 1.3 with suppressing the electron current. The beam divergence angle is also maintained small enough, 4 mrad.
Tobari, Hiroyuki; Inoue, Takashi; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Dairaku, Masayuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Sakamoto, Keishi; Kuriyama, Masaaki*; et al.
Fusion Engineering and Design, 88(6-8), p.975 - 979, 2013/10
Times Cited Count：1 Percentile：10.69(Nuclear Science & Technology)The HV bushing, one of the ITER NB components, which is to be procured by JADA, is a multi-conductor feed through composed of five-stage double-layered insulator columns with large brazed ceramic ring and fiber reinforced plastic (FRP) ring. The HV bushing is a bulk head between insulation gas at 0.6 MPa and vacuum. The FRP ring is required to sustain the pressure load, seismic load and dead weight. Brazing area of the ceramic ring with Kovar is required to maintain vacuum leak tightness and pressure tightness against the air filled at 0.6 MPa. To design the HV bushing satisfying the safety factor of 
3.5, mechanical analyses were carried out. As for the FRP ring, it was confirmed that isotropic fiber cloth FRP rings should be used for sufficient strength against shear stress. Also, shape and fixation area of the Kovar sleeve were modified to lower the stress at the joint area. As a result, a design of the insulator for the HV bushing was established satisfying the requirement.
Sn conductors for ITER central solenoidsNabara, Yoshihiro; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; Takahashi, Yoshikazu; Matsui, Kunihiro; Koizumi, Norikiyo; et al.
IEEE Transactions on Applied Superconductivity, 23(3), p.4801604_1 - 4801604_4, 2013/06
Times Cited Count：10 Percentile：48(Engineering, Electrical & Electronic)no abstracts in English
Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; Dairaku, Masayuki; Tobari, Hiroyuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Inoue, Takashi; DeEsch, H. P. L.*; Grisham, L. R.*; et al.
AIP Conference Proceedings 1515, p.227 - 236, 2013/02
Times Cited Count：12 Percentile：96.1(Physics, Applied)In a five stage multi-aperture multi-grid (MAMuG) accelerator for the ITER neutral beam injector (NBI), 1 MeV, 40 A D
ion beam is required for 1 hour. However, beamlets are deflected due to (1) magnetic field for electron suppression and (2) space charge repulsion between beamlets, and consequently, cause excess grid heat load. A three dimensional beam analysis has been carried out to compensate the beamlet deflections. This paper shows that the beamlet deflections due to (1) and (2) are compensated by an aperture offset of only 0.6 mm applied to the aperture of 17 mm in diameter in the extractor and by a metal bar attached around aperture area beneath the extractor, respectively. When the metal bar is increased to 3 mm in thickness and installed 30 mm away from the aperture area, the beamlet is steered gently by the weaker electric field distortion. The beam optics was confirmed not deteriorated by those compensations. The presentation also discusses application of these compensation techniques to the ITER design.
Shibata, Takanori; Terasaki, Ryo*; Kashiwagi, Mieko; Inoue, Takashi; Dairaku, Masayuki; Taniguchi, Masaki; Tobari, Hiroyuki; Umeda, Naotaka; Watanabe, Kazuhiro; Sakamoto, Keishi; et al.
AIP Conference Proceedings 1515, p.177 - 186, 2013/02
Times Cited Count：8 Percentile：92.97(Physics, Applied)In the neutral beam injector in JT-60SA, one of issues is that negative ion beam is partially intercepted at acceleration grids due to a spatial non-uniformity of negative ion production on large extraction area (0.9
0.45m). Previous experiments showed that fast electrons emitted from filament cathodes are transported in a longitudinal direction by 
drift and the spatial distribution of electron temperature (
) strongly relates with the non-uniformity. In this study, a three-dimensional electron transport analysis has been developed. Electron temperature in the analysis agreed well with measurements in JAEA 10A ion source. This study clarified that the bias of distribution are caused by the following reasons; (1) fast electrons drifted in the longitudinal direction survives near the end wall with energy up to 
= 25-60 eV and (2) they produces thermal electrons by collision with plasma particles there.
H ion beam acceleration at JAEA for the ITER neutral beam injectorTobari, Hiroyuki; Taniguchi, Masaki; Kashiwagi, Mieko; Dairaku, Masayuki; Umeda, Naotaka; Yamanaka, Haruhiko; Tsuchida, Kazuki; Takemoto, Jumpei; Watanabe, Kazuhiro; Inoue, Takashi; et al.
Plasma Science and Technology, 15(2), p.179 - 183, 2013/02
Times Cited Count：1 Percentile：4.39(Physics, Fluids & Plasmas)Vacuum insulation is a common issue for the accelerator and the HV bushing for the ITER NBI. The HV bushing has five-stage structure and each stage consists of double-layered insulators. Hence, several triple points exist around the insulators. To reduce electric field at those points simultaneously, three types of stress ring were developed. In voltage holding test of a full-scale mockup equipped with those stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, voltage holding capability was not sufficient due to breakdown triggered by electric field concentration at edge and corner on grid components. By extending gap length, 1 MV was sustained in vacuum. Furthermore, with new accelerator grids which compensates beam deflection due to magnetic field and space charge repulsion between beamlets, 980 keV, 185 A/m H ion beam acceleration was demonstrated, which was close to ITER requirement.
Wakui, Ryohei; Kitagaki, Toru; Higuchi, Hidetoshi; Takeuchi, Masayuki; Koizumi, Kenji; Washiya, Tadahiro
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 7 Pages, 2012/07
Sn conductors for ITER toroidal field coilsNabara, Yoshihiro; Nunoya, Yoshihiko; Isono, Takaaki; Hamada, Kazuya; Takahashi, Yoshikazu; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Ebisawa, Noboru; et al.
IEEE Transactions on Applied Superconductivity, 22(3), p.4804804_1 - 4804804_4, 2012/06
Times Cited Count：18 Percentile：65.46(Engineering, Electrical & Electronic)no abstracts in English
Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Dairaku, Masayuki; Takemoto, Jumpei; Tobari, Hiroyuki; Tsuchida, Kazuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Kojima, Atsushi; et al.
Review of Scientific Instruments, 83(2), p.02B121_1 - 02B121_3, 2012/02
Times Cited Count：11 Percentile：46.97(Instruments & Instrumentation)JAEA has developed the MeV accelerator to demonstrate 1 MeV, 200 A/m H ion beam acceleration required for ITER NBI. A key to realize such a high power accelerator is improvement of voltage holding capability. Based on detailed investigation of the voltage holding characteristics, MeV accelerator was modified to reduce electric field concentration by extending gaps between the grid supports and increasing curvature radiuses at the support corners. After the modifications, accelerator succeeded in sustaining -1 MV in vacuum without beam acceleration. Moreover, beam deflection due to the magnetic field for electron suppression and space charge repulsion was compensated by aperture displacement technique. As the result, beam deflection was compensated and voltage holding during the beam acceleration was improved. Beam parameter of the MeV accelerator was increased to 980 keV, 185 A/m, which is close to the requirement of ITER accelerator.
Shibata, Takanori; Koga, Shojiro*; Terasaki, Ryo*; Inoue, Takashi; Dairaku, Masayuki; Kashiwagi, Mieko; Taniguchi, Masaki; Tobari, Hiroyuki; Tsuchida, Kazuki; Umeda, Naotaka; et al.
Review of Scientific Instruments, 83(2), p.02A719_1 - 02A719_3, 2012/02
Times Cited Count：2 Percentile：12.31(Instruments & Instrumentation)In the NBI for large fusion devices, production of uniform negative ion beam is one of important issues. A physical model is proposed to understand the non-uniformity. It has been qualitatively shown that the non-uniform beam intensity is due to the following process; (1) formation of non-uniform EEDF, (2) localized production of hydrogen atoms/ions (H
/H
) due to (1), (3) non-uniform flux of H/H to the PG and (4) localized surface production of negative ions. However, in the past studies, the EEDF was assumed as two temperature Maxwellian distribution from measurements. Thus effects of high energy electrons are not taken into account precisely. In the present research, local EEDF is calculated by the 3D Monte-Carlo kinetic model which takes into account the spatial and magnetic configurations of the real negative ion source. The numerical result show that high energy component of the EEDF enhances the spatial non-uniformity in the production rate of H/H.
Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Dairaku, Masayuki; Yamanaka, Haruhiko; Tsuchida, Kazuki; Kojima, Atsushi; et al.
AIP Conference Proceedings 1390, p.449 - 456, 2011/09
Times Cited Count：2 Percentile：53.22(Physics, Atomic, Molecular & Chemical)At JAEA, MeV accelerator has been developed as a proof-of-principle accelerator for ITER NBI. To achieve the acceleration of 1 MeV, 200 A/m beam required for ITER, improvement of the voltage holding capability is essential. Review of voltage holding results ever obtained with various geometries of the accelerators showed that voltage holding capability was about a half of that for ideal small electrode. This is due to local electric field concentration in the accelerators, such as edge and corner between grids and its support structures. Based on these results, accelerator was modified to reduce the electric field concentration by reshaping the support structures and expanding the gap length. After the modifications, voltage holding capability in vacuum was increased from 835 kV to 1 MV. Voltage holding progressed the energy and current to 879 keV, 0.36 A (157 A/m).
