Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
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
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.
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:10 Percentile:64.63(Nuclear Science & Technology)no abstracts in English
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:33.25(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.
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:272 Percentile:99.03(Physics, Multidisciplinary)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
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:30.92(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:11 Percentile:15.13(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:115 Percentile:95.84(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 1.310m at the well-controlled Pt/YIG interface, which is close to a theoretical prediction.
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:30.71(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.
Jeong, J. H.*; Bae, Y. S.*; Joung, M.*; Kim, H. J.*; Park, S. I.*; Han, W. S.*; Kim, J. S.*; Yang, H. L.*; Kwak, J. G.*; Sakamoto, Keishi; et al.
Fusion Engineering and Design, 88(5), p.380 - 387, 2013/06
Times Cited Count:3 Percentile:25.73(Nuclear Science & Technology)An, Toshu*; Vasyuchka, V. I.*; Uchida, Kenichi*; Chumak, A. V.*; Yamaguchi, Kazuya*; Harii, Kazuya; Oe, Junichiro*; Jungfleisch, M. B.*; Kajiwara, Yosuke*; Adachi, Hiroto; et al.
Nature Materials, 12(6), p.549 - 553, 2013/06
Times Cited Count:126 Percentile:96.33(Chemistry, Physical)Kobayashi, Takayuki; Isayama, Akihiko; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Wada, Kenji; Sato, Yoshikatsu; Hinata, Jun; Yokokura, Kenji; et al.
Fusion Science and Technology, 63(1T), p.160 - 163, 2013/05
Times Cited Count:7 Percentile:49.28(Nuclear Science & Technology)A dual frequency electron cyclotron range of frequency system has been developed for JT-60SA, by which a second frequency (135 140 GHz) is generated in addition to the first frequency of 110 GHz. A development of a dual frequency gyrotron is a key to realize the dual frequency system. The second frequency was chosen to be 138 GHz from the above frequency range from the viewpoint of gyrotron design. In order to realize high-power ( 1 MW) and long-pulse operation for both frequencies, we designed main components of the gyrotron (the diamond window, cavity resonator and quasi-optical mode converter). We found the optimum parameter set from the parameters of these components, which has discrete characteristics. It was confirmed that the output power higher than 1 MW is obtained for both frequencies as a result of numerical design. Based on the above design, a dual frequency gyrotron was newly fabricated. In the conditioning operation, an output power was obtained as we expected.
Takahashi, Koji; Iida, Hiromasa*; Kobayashi, Noriyuki*; Kajiwara, Ken; Sakamoto, Keishi; Omori, Toshimichi*; Henderson, M.*
Fusion Science and Technology, 63(1T), p.156 - 159, 2013/05
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)Nuclear analysis of the ITER equatorial EC launcher has been carried out to determine heat and/or particle loads on its components and also to evaluate the possibility of "hands-on maintainability" (personnel accessibility) to the launcher back-end. Monte Carlo code "MCNP5" is applied to simulate the radiation leak from fusion plasma to the special region around the launcher. The results indicate a significant radiation leak at the gaps between the port walls and port plug frame and at the waveguide bundles in the launcher. Another significant neutron leakage is through the port wall consisting of only stainless steel but without light isotopes such as water. The shut down dose rates was estimated at the port interspace behind the launcher at the level of the required value of 100 Sv/h. This analysis offers the potential to modify the launchers shielding layout to minimize the above leakage and further reduce the shut down dose rates in the regions of personnel access.
Kajiwara, Ken; Oda, Yasuhisa; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi
Fusion Science and Technology, 63(1T), p.35 - 39, 2013/05
Times Cited Count:2 Percentile:18.63(Nuclear Science & Technology)Kajiwara, Ken; Sakamoto, Keishi; Oda, Yasuhisa; Hayashi, Kazuo*; Takahashi, Koji; Kasugai, Atsushi
Nuclear Fusion, 53(4), p.043013_1 - 043013_5, 2013/04
Times Cited Count:18 Percentile:62.36(Physics, Fluids & Plasmas)Uchida, Kenichi*; Nonaka, Tatsumi*; Kikkawa, Takashi*; Kajiwara, Yosuke*; Saito, Eiji
Physical Review B, 87(10), p.104412_1 - 104412_6, 2013/03
Times Cited Count:98 Percentile:94.73(Materials Science, Multidisciplinary)The longitudinal spin Seebeck effect (LSSE) is investigated in various garnet ferritesYFeO ( = Gd, Ca; = Al, Mn, V, In, Zr) by means of the inverse spin Hall effect in Pt films. The magnitude of the LSSE voltage in the Pt/YFeO samples is found to be enhanced with increasing concentration of Fe in the garnet ferrites, which can be explained by a change in the spin-mixing conductance at the Pt/YFeO interfaces. We also investigate the dependence of the LSSE voltage on macroscopic magnetic parameters of YFeO. The experimental results show that the LSSE voltage in the Pt/YFeO samples hasa positive correlation with the Curie temperature and the saturation magnetization, but no clear correlation with the gyromagnetic ratio and the Gilbert damping constant of the samples.
Takahashi, Koji; Kajiwara, Ken; Oda, Yasuhisa; Kobayashi, Noriyuki*; Sakamoto, Keishi; Omori, Toshimichi*; Henderson, M.*
Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03
The ITER equatorial EC launcher is making a large technology to injecting 20 M and CW operation. The design of the shield blanket structure that tolerates thermal and electromagnetic load is attained. The port plug structure considering the fabrication process applying HIP and TIG-welding are designed. The mm-wave design that enables to guide the wave power of 20 MW into plasma with toroidal steering capability of 20 40 and efficiency of 98.4 99% assuming HE11 fundamental wave mode + TEM000 gaussian mode are proceeded. Reduction of the heat load to 2.1 MW/m on the steering mirror are attained. These results allow the transmission of 2.0 MW per a waveguide and the required radiation profile from the launcher. The full scale mock-up of the mm-wave launching system consisting of the waveguides and the mirrors and the subcomponents such as the steering mechanism of the mirror, the cooling water lines and etc., are fabricated to investigate the design availability. High power (0.5 MW) experiment of the mock-up confirmed the expected wave beam propagation and steering capability of 20 40. The mock-up of the shield blanket module and the partial mock-up of the port plug structure are fabricated based on the present design to investigate the manufacturability and the performance of the cooling water flow. The results will reflect back to the fabrication design of the structural components of the equatorial launcher.
Jungfleisch, M. B.*; An, Toshu*; Ando, Kazuya*; Kajiwara, Yosuke*; Uchida, Kenichi*; Vasyuchka, V. I.*; Chumak, A. V.*; Serga, A. A.*; Saito, Eiji; Hillebrands, B.*
Applied Physics Letters, 102(6), p.062417_1 - 062417_4, 2013/02
Times Cited Count:48 Percentile:85.77(Physics, Applied)Takahashi, Koji; Kajiwara, Ken; Oda, Yasuhisa; Sakamoto, Keishi; Omori, Toshimichi*; Henderson, M.*
Fusion Engineering and Design, 88(2), p.85 - 93, 2013/02
Times Cited Count:7 Percentile:49.28(Nuclear Science & Technology)The design of the torus diamond window for the ITER electron cyclotron heating and current drive (EC H&CD) system has advanced considering a reliable and manufacturable structure. The diamond window prototype was fabricated in basis of the design and the high power experiment was carried out to verify the millimeter wave transmission capability. Transmission of 740 kW-100 sec was demonstrated and no significant temperature increase of the window structure and no damage on the diamond disk was obtained. The saturation of the cooling water for the window was observed and loss tangent of 7.8 10, which was the lowest value that we had ever obtained at JAEA, was evaluated. This result indicates that the diamond window design is feasible and promising the high power more than 1 MW transmission.
Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Mitsunaka, Yoshika*; Sakamoto, Keishi
Review of Scientific Instruments, 84(1), p.013501_1 - 013501_6, 2013/01
Times Cited Count:6 Percentile:30.78(Instruments & Instrumentation)