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Hirano, Koichiro; Fukuda, Makoto*; Ezato, Koichiro*; Tokunaga, Kazutoshi*
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.415 - 419, 2023/11
Tungsten is used in beam targets and experimental fusion reactor (ITER) divertors as a material with low activation, high thermal conductivity and high strength properties. Using a 3 MeV linac with negative hydrogen ion beam energy, multiple irradiation tests were conducted on tungsten materials meeting the ITER requirements, in which temperature changes of heating and cooling were repeatedly given at 5 Hz cycles. As a result, protrusions and cracks were observed on the surface of the test piece using SEM device, which were presumably caused by repeated expansion and contraction due to rapid pulse-like temperature change.
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Komabuchi, Mai*; Urushihara, Daisuke*; Asaka, Toru*; Fukuda, Koichiro*; Ohara, Takashi; Munakata, Koji*; Ishikawa, Yoshihisa*
Journal of the Physical Society of Japan, 89(3), p.034601_1 - 034601_5, 2020/03
Times Cited Count：2 Percentile：17.68(Physics, Multidisciplinary)
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apatite without interstitial oxygens due to the overbonded channel oxygensFujii, Kotaro*; Yashima, Masatomo*; Hibino, Keisuke*; Shiraiwa, Masahiro*; Fukuda, Koichiro*; Nakayama, Susumu*; Ishizawa, Nobuo*; Hanashima, Takayasu*; Ohara, Takashi
Journal of Materials Chemistry A, 6(23), p.10835 - 10846, 2018/06
Times Cited Count：30 Percentile：67.85(Chemistry, Physical)Kondo, Yasuhiro; Morishita, Takatoshi; Yamazaki, Saishun; Hori, Toshihiko; Sawabe, Yuki; Chishiro, Etsuji; Fukuda, Shimpei; Hasegawa, Kazuo; Hirano, Koichiro; Kikuzawa, Nobuhiro; et al.
Physical Review Special Topics; Accelerators and Beams, 17(12), p.120101_1 - 120101_8, 2014/12
Times Cited Count：6 Percentile：41.13(Physics, Nuclear)We performed a beam test of a new radio frequency quadrupole linac (RFQ III) for the beam current upgrade of the Japan Proton Accelerator Research Complex. First, the conditioning of RFQ III was conducted, and after 20 h of conditioning, RFQ III became very stable with a nominal peak power and duty factor of 400 kW and 1.5%, respectively. An off-line beam test was subsequently conducted before installation in the accelerator tunnel. The transmission, transverse emittance, and energy spread of the 50-mA negative hydrogen beam from RFQ III were measured and compared with simulation results. The experiment and simulation results showed good agreement; therefore, we conclude that the performance of RFQ III conforms to its design.
Kawane, Yusuke*; Miura, Akihiko; Miyao, Tomoaki*; Hirano, Koichiro; Sugimura, Takashi*; Kato, Yuko; Sawabe, Yuki; Fukuda, Shimpei; Ouchi, Nobuo
Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1288 - 1291, 2014/10
In the J-PARC Linac, because an upgrading of a beam current up to 50mA using an RF-driven ion source and a new RFQ Linac cavity is in progress, we have developed a new frontend equipments. In order to protect the scraper against 50 mA, we need to observe the temperature and to avoid the excess heat loading of the scraper surface and to count the irradiated beam particles. We also monitor the beam transmission between the upstream and downstream of the chopper cavity to check the chopping errors using the beam current monitors. We fabricated the interlock system for the temperature, irradiated particle numbers and beam transmission. And we tested them in the test stand with actual beam. This paper describes the interlock system and their test results.
Yamazaki, Yoshio; Hirano, Koichiro*; Fukuda, Satoshi*; Takano, Mikio*; Araki, Sakae*; Terunuma, Nobuhiro*; Urakawa, Junji*
Proceedings of 9th European Particle Accelerator Conference (EPAC 2004), 0 Pages, 2004/07
Focusing on the cover layer materials (as the Radon Barrier Materials), which could have the effect to restrain the radon from scattering into the air and the effect of the radiation shielding, we produced the radon barrier materials with crude bentonite on an experimental basis, using the rotary type comprehensive unit for grinding and mixing, through which we carried out the evaluation of the characteristics thereof.
Hirano, Koichiro; Fukuda, Makoto*; Ezato, Koichiro*; Tokunaga, Kazutoshi*
no journal, ,
The beam targets of the J-PARC linac are multiply irradiated by hydrogen negative ion beams with beam energy of 3 MeV. The purpose of this study is to clarify the pulsed heat load conditions that can withstand multiple irradiations when beam targets made of tungsten materials are used. Using an off-line beam test-stand with a 3 MeV hydrogen negative ion beam, multiple irradiation tests were conducted on tungsten materials for ITER, in which temperature changes of heating (3200 degree) and cooling (160 degree) were repeatedly given at a period of 5 Hz. This paper reports on the surface observation of the tungsten materials and the partial pressure measurements by a quadrupole mass spectrometer.
Fukuda, Makoto*; Hirano, Koichiro; Tokunaga, Kazutoshi*; Ezato, Koichiro*
no journal, ,
Tungsten which is used as a plasma-facing material for ITER divertor is expected to receive heat flux under various conditions during ITER operation. Therefore, it is necessary to understand the modification of tungsten surface under various heat load conditions. In this work, as part of the investigation of the repeated short pulse heat load effect on tungsten, the effect of multiple irradiation (3MeV, 5Hz) with a negative hydrogen ion beam was evaluated. As a result, unevenness and cracks were observed on the surface after irradiation, and different surface modification behavior was observed compared with previous experiment which performed with almost constant heat load (10s On and 20-30 s Off as one cycle).
Tokunaga, Kazutoshi*; Nomiyama, Yukino*; Fukuda, Makoto*; Ezato, Koichiro*; Hirano, Koichiro
no journal, ,
The surface modification of tungsten materials exposed by multiple irradiations of a negative hydrogen ion beam is examined to investigate the influence of the repeated short pulse heat loading. Grid-like cracks are formed on the sample surfaces which the surface is perpendicular to the rolling direction. On the other hand, ellipsoidal cracks are formed on the sample surfaces which the surface is parallel to the rolling direction. These results show crack formation is different depending on the orientation of grain boundaries. The surface modification by plastic formation due to the repeated heat loading in the center area surrounded by the cracks is observed. Furthermore, in the case of high heat loading conditions, a number of cone-like protuberances are melted and resolidified, and deep cracks are formed in the vicinity. The peculiar surface such as the deep cracks and the cone-like protuberances are formed.
Fukuda, Makoto*; Tokunaga, Kazutoshi*; Ezato, Koichiro*; Hirano, Koichiro
no journal, ,
Tungsten which is used as a plasma-facing material of the ITER divertor, is expected to receive various type of heat load during ITER operation. Therefore, it is necessary to understand the surface damage of tungsten under various heat load conditions. In this study, as part of the investigation of the effects of short-pulse repetitive heat loads on tungsten, the effects of multiple irradiations of the negative hydrogen ion beam (3 MeV, 5 Hz) on the surface of tungsten were investigated. As a result of the investigation, it was clarified that microcracks were formed on the surface of tungsten exposed to multiple irradiations, and that the microstructure was also changed.
Tokunaga, Kazutoshi*; Nomiyama, Yukino*; Fukuda, Makoto*; Ezato, Koichiro*; Hirano, Koichiro
no journal, ,
It is known that the surface temperature of tungsten (W) divertor during the slow transient at steady state plasma operation in ITER will be higher than that of the recrystallization temperature. Therefore, thermal behavior of recrystallized W(RC-W) exposed the expecting heat loadings during ITER plasma operation is necessary to be investigated. In the present work, RC-W has been exposed to multiple irradiation of negative hydrogen ion beam (3 MeV, 5 Hz) and the effect of repeated short pulse heat loading on surface modification has been investigated. The results have also compared with that of stress-relieved W (SR-W). The area of surface modification of RC-W is larger than that of SR-W in the case of a peak temperature of 1650 degree. The circular cracks along grain boundaries are formed and complex surface modification including line like uneven surface are seen. These modifications of RC-W are different from that of SR-W.
