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Suzuki, Kenji*; Kura, Komoe*; Miura, Yasufumi*; Shiro, Ayumi*; Toyokawa, Hidenori*; Saji, Choji*; Kajiwara, Kentaro*; Shobu, Takahisa
Zairyo, 71(12), p.1005 - 1012, 2022/12
This paper describes a stress measurement from a welded part of an austenitic stainless steel using synchrotron X-rays. Difficulty measuring the X-ray stress of the welded part is caused by the broadening of the diffraction spot in the radial and circumferential directions. The bending strains of the rectangular bar made of the welded part were measured using synchrotron white X-rays and the double exposure method. To improve the energy resolution, monochromatic synchrotron X-ray of 70 keV was used. The diffraction pattern showed the sharp arc like a pattern from texture material. The diffraction profile was obtained from the integral of the diffraction intensity in the direction of the circumference. The diffraction angle was determined using the double exposure method. As a result, the distribution of the residual stresses of the welded part could be measured.
Sugano, Michinaka*; Machiya, Shutaro*; Shobu, Takahisa; Shiro, Ayumi*; Kajiwara, Kentaro*; Nakamoto, Tatsushi*
Superconductor Science and Technology, 33(8), p.085003_1 - 085003_10, 2020/08
Times Cited Count：8 Percentile：35.59(Physics, Applied)Miyakawa, Susumu*; Ito, Toshimasa*; Iwahori, Keisuke*; Aoyama, Yoshihiko*; Kubo, Ryosuke*; Murata, Shinji*; Shobu, Takahisa; Shiro, Ayumi*; Kajiwara, Kentaro*
Zairyo, 69(4), p.308 - 314, 2020/04
White etching area which looks white with nital corrosive liquid may be recognized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial X-ray measurement equipment (B method) were investigated. The former was modified by surface residual stress according to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
110
and 100 oriented REBCO tapesOsamura, Kozo*; Machiya, Shutaro*; Kajiwara, Kentaro*; Kawasaki, Takuro; Harjo, S.; Zhang, Y.*; Fujita, Shinji*; Iijima, Yasuhiro*; Hampshire, D. P.*
AIP Advances (Internet), 9(7), p.075216_1 - 075216_11, 2019/07
Times Cited Count：12 Percentile：45.89(Nanoscience & Nanotechnology)Toyokawa, Hidenori*; Saji, Choji*; Kawase, Morihiro*; Wu, S.*; Hurukawa, Yukihito*; Kajiwara, Kentaro*; Sato, Masugu*; Hirono, Toko*; Shiro, Ayumi*; Shobu, Takahisa; et al.
Journal of Instrumentation (Internet), 12(1), p.C01044_1 - C01044_7, 2017/01
Times Cited Count：6 Percentile：26.29(Instruments & Instrumentation)We have been developing CdTe pixel detectors combined with a Schottky diode sensor and photon-counting ASICs. The hybrid pixel detector was designed with a pixel size of 200 micro-meter by 200 micro-meter and an area of 19 mm by 20 mm or 38.2 mm by 40.2 mm. The photon-counting ASIC, SP8-04F10K, has a preamplifier, a shaper, 3-level window-type discriminators and a 24-bits counter in each pixel. The single-chip detector with 100 by 95 pixels successfully operated with a photon-counting mode selecting X-ray energy with the window comparator and stable operation was realized at 20
C. We have performed a feasibility study for a white X-ray microbeam experiment. Laue diffraction patterns were measured during the scan of the irradiated position in a silicon steel sample. The grain boundaries were identified by using the differentials between adjacent images at each position.
Oshima, Katsumi; Oda, Yasuhisa; Takahashi, Koji; Terakado, Masayuki; Ikeda, Ryosuke; Hayashi, Kazuo*; Moriyama, Shinichi; Kajiwara, Ken; Sakamoto, Keishi
JAEA-Technology 2015-061, 65 Pages, 2016/03
JAEA-Technology-2015-061.pdf:24.28MB
In JAEA, an ITER relevant control system for ITER gyrotron was developed according to Plant Control Design Handbook. This control system was developed based on ITER CODAC Core System and implemented state machine control of gyrotron operation system, sequential timing control of gyrotron oscillation startup, and data acquisition. The operation of ITER 170 GHz gyrotron was demonstrated with ITER relevant power supply configuration. This system is utilized for gyrotron operation test for ITER procurement. This report describes the architecture of gyrotron operation system, its basic and detailed design, and recent operation results.
Nakatani, Hayato*; Kajiwara, Kentaro*; Akita, Koichi; Ogihara, Shinji*
Proceedings of 14th Japan International SAMPE Symposium & Exhibition (JISSE-14) (USB Flash Drive), 6 Pages, 2015/12
Takahashi, Koji; Abe, Ganji; Kajiwara, Ken; Oda, Yasuhisa; Isozaki, Masami; Ikeda, Ryosuke; Sakamoto, Keishi; 2 of others*
Fusion Engineering and Design, 96-97, p.602 - 606, 2015/10
The recent physics analysis reveals that there is the potential to more than double the drive current at the range of 
= 0.4
0.6 if a beam steering direction can be modified from toroidal to poloidal. However, the change of steering direction has a significant impact on the design of the Equatorial EC Launcher (EL), especially, mm-wave propagation and blanket shield modules (BSMs) and a knock-on effect impacting the internal shield structure. The EL has three sets of mm-wave beam row and each is composed of eight waveguide lines and a quasi-optical transmission region that is formed a steering and fixed mirror, locating in front of the waveguide outlet. It has been successfully performed that the outstanding configuration of the mirrors is developed, the mirror actuator is changed from the push-pull to pneumatic concept and the modification of the internal shield structure is minimized as much as possible. This creative modification ensures that both mm-wave beams from the middle and bottom row pass through the same BSM opening and then, the feasible and reliable design of BSMs can be carried out. The nuclear analysis of this design modification shows that the residual dose rate at the launcher back end is reduced by 20%. This paper summarizes that the possible solution of the mm-wave design modification enhancing the off axis current drive functionality is developed and ensures the effective mm-wave propagation, feasible design of the EL BSMs and nuclear shield structure.
Omori, Toshimichi*; Albajar, F.*; Bonicelli, T.*; Darbos, C.*; Denisov, G.*; Gassmanna, T.*; Hanson, G.*; Kajiwara, Ken; Oda, Yasuhisa; Purohit, D.*; et al.
Fusion Engineering and Design, 96-97, p.547 - 552, 2015/10
An electron cyclotron (EC) system is one of four auxiliary plasma heating systems to be installed in ITER tokamak. The ITER EC system consists of 24 gyrotrons (RFPS: RF power source) with associated 12 high voltage power supplies (HVPSs), a set of evacuated transmission lines (TLs) and two types of launchers. The whole system is designed compatible with propagation of 170 GHz of up to 20 MW microwave power into the plasma. The primary functions of the system include plasma start-up, central heating and current drive (H&CD) and magneto-hydrodynamic (MHD) instabilities control. The design takes present day technology and extends toward high power CW operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond. The EC system is faced with significant challenges, which not only includes an advanced microwave system for plasma heating and current drive applications but also has to comply with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012. Since conceptual design of the EC system established in 2007, the EC system has progressed to a preliminary design stage in 2012, and is now moving forward toward a final design. The majority of the subsystems are getting to knuckle down the detailed design to realize the future advancement envisioned toward the final design completion.
Takahashi, Koji; Kajiwara, Ken; Oda, Yasuhisa; Sakamoto, Keishi; Omori, Toshimichi*; Henderson, M.*
Fusion Science and Technology, 67(4), p.718 - 731, 2015/05
Times Cited Count：4 Percentile：29.15(Nuclear Science & Technology)Development of an electron cyclotron (EC) equatorial launcher has been undergoing a series of prototype tests and design enhancements intending to improve reliability and functionality of the launcher. The design enhancements include adaptation of the launcher steering angles such that one of three beam rows of the launcher is necessary flipped to perform counter current drive (to conform to a new ITER physics requirement). Also the top and bottom steering rows have been tilted with angle of 5 so that the top and bottom beam row can access from on axis to near mid-radius. Furthermore, the position of the focusing mirror that forms a quasi-optical in-vessel millimeter wave transmission line is modified to increase the nuclear shielding capability. High power experiment of the mm-wave launching system mock-up fabricated in basis of the design confirmed the successful steering capability of 2040. It was measured that some of stray RF propagated in the beam duct and generated some heat on the duct at a certain condition of mm-wave transmission. Prototype tests also include the fabrication of the blanket shield module and the partial port plug mock-up and have shown no serious technological issue on the fabrication and the cooling functionality.
Hada, Kazuyoshi*; Nagasaki, Kazunobu*; Masuda, Kai*; Kobayashi, Shinji*; Ide, Shunsuke; Isayama, Akihiko; Kajiwara, Ken
Fusion Science and Technology, 67(4), p.693 - 704, 2015/05
Times Cited Count：11 Percentile：65.38(Nuclear Science & Technology)no abstracts in English
Shiomi, Yuki*; Nomura, Kentaro*; Kajiwara, Yosuke*; Eto, Kazuma*; Novak, M.*; Segawa, Koji*; Ando, Yoichi*; Saito, Eiji
Physical Review Letters, 113(19), p.196601_1 - 196601_5, 2014/11
Times Cited Count：299 Percentile：98.94(Physics, Multidisciplinary)Osamura, Kozo*; Machiya, Shutaro*; Hampshire, D. P.*; Tsuchiya, Yoshinori*; Shobu, Takahisa; Kajiwara, Kentaro*; Osabe, Goro*; Yamazaki, Kohei*; Yamada, Yuichi*; Fujikami, Jun*
Superconductor Science and Technology, 27(8), p.085005_1 - 085005_11, 2014/08
Times Cited Count：32 Percentile：74.27(Physics, Applied)Oda, Yasuhisa; Oshima, Katsumi; Nakamoto, Takashi*; Hashimoto, Yasunori*; Yamamoto, Tsuyoshi; Hayashi, Kazuo*; Ikeda, Yukiharu; Ikeda, Ryosuke; Kajiwara, Ken; Takahashi, Koji; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 90(7), p.365 - 373, 2014/07
no abstracts in English
Shibano, Junichi*; Kajiwara, Kentaro*; Tsukamoto, Takuya*; Kawai, Hirokazu*; Miura, Setsuo*; Zhang, S.*; Shobu, Takahisa
Zairyo, 63(7), p.533 - 538, 2014/07
A ductile damage progress of an aluminum single crystal with the prior activity of the single slip system under tensile loading was verified by a profile analysis using white X-ray obtained in BL28B2 beam line of SPring-8. In profile analysis, an instrumental function was defined in consideration both of a divergence by slits and a response function peculiar to the energy dispersive method. As a result, dislocation density increased as ductile damage progressed, but it was relatively low near the notch. The influence of a release of the strain energy by a ductile damage progress was expected. The characteristics of ductile damage progress near the notch of the aluminum single crystal with a prior activity of a single slip system under the tensile loading were clarified from the distribution of dislocation density.
Shibano, Junichi*; Kajiwara, Kentaro*; Tsukamoto, Takuya*; Kawai, Hirokazu*; Miura, Setsuo*; Zhang, S.*; Shobu, Takahisa; Kobayashi, Michiaki*
Materials Science Forum, 777, p.176 - 181, 2014/02
Times Cited Count：2 Percentile：69.12(Materials Science, Multidisciplinary)Kajiwara, Ken; Takahashi, Koji; Oda, Yasuhisa; Kobayashi, Noriyuki*; Sakamoto, Keishi
Fusion Engineering and Design, 89(1), p.6 - 10, 2014/01
Times Cited Count：4 Percentile：27.54(Nuclear Science & Technology)Uchida, Kenichi*; Adachi, Hiroto; Kajiwara, Yosuke*; Maekawa, Sadamichi; Saito, Eiji
Solid State Physics, 64; Recent Advances in Magnetic Insulators; From Spintronics to Microwave Applications, p.1 - 27, 2013/11
Times Cited Count：14 Percentile：17.43(Physics, Condensed Matter)Qiu, Z.*; Ando, Kazuya*; Uchida, Kenichi*; Kajiwara, Yosuke*; Takahashi, Ryo*; Nakayama, Hiroyasu*; An, Toshu*; Fujikawa, Yasunori*; Saito, Eiji
Applied Physics Letters, 103(9), p.092404_1 - 092404_4, 2013/08
Times Cited Count：123 Percentile：95.75(Physics, Applied)A platinum (Pt)/yttrium iron garnet (YIG) bilayer system with a well-controlled interface has been developed; spin mixing conductance at the Pt/YIG interface has been studied. A clear interface with good crystal perfection is experimentally demonstrated to be one of the important factors for an ultimate spin mixing conductance. The spin mixing conductance is obtained to be 1.3
10
m
at the well-controlled Pt/YIG interface, which is close to a theoretical prediction.
Fe
O
Kajiwara, Yosuke*; Uchida, Kenichi*; Kikuchi, Daisuke*; An, Toshu*; Fujikawa, Yasunori*; Saito, Eiji
Applied Physics Letters, 103(5), p.052404_1 - 052404_4, 2013/07
Times Cited Count：7 Percentile：28.65(Physics, Applied)Heat-current-induced manipulation of spin relaxation in YFeO under an in-plane temperature gradient is investigated. We show that the linewidth of the ferromagnetic resonance spectrum, i.e., the spin relaxation, in an YFeO film increases or decreases depending on the temperature-gradient direction and that this modulation is attributed to the spin-transfer torque caused by a thermally induced transverse spin-wave spin current in the YFeO film. The experimental results also show that the spin-current magnitude generated by spin pumping in an attached Pt film is inversely proportional to the square of the modulated Gilbert damping constant, consistent with a phenomenological spin-pumping model.
