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Yoshimoto, Masahiro*; Fujita, Manami; Hashimoto, Tadashi; Hayakawa, Shuhei; Ichikawa, Yudai; Ichikawa, Masaya; Imai, Kenichi*; Nanamura, Takuya; Naruki, Megumi; Sako, Hiroyuki; et al.
Progress of Theoretical and Experimental Physics (Internet), 2021(7), p.073D02_1 - 073D02_19, 2021/07
Times Cited Count：13 Percentile：81.3(Physics, Multidisciplinary)Sako, Hiroyuki; Harada, Hiroyuki; Sakaguchi, Takao*; Chujo, Tatsuya*; Esumi, Shinichi*; Gunji, Taku*; Hasegawa, Shoichi; Hwang, S.; Ichikawa, Yudai; Imai, Kenichi; et al.
Nuclear Physics A, 956, p.850 - 853, 2016/12
Times Cited Count：12 Percentile：65.66(Physics, Nuclear)Nishikiori, Ryo; Kojima, Atsushi; Hanada, Masaya; Kashiwagi, Mieko; Watanabe, Kazuhiro; Umeda, Naotaka; Tobari, Hiroyuki; Yoshida, Masafumi; Ichikawa, Masahiro; Hiratsuka, Junichi; et al.
Plasma and Fusion Research (Internet), 11, p.2401014_1 - 2401014_4, 2016/03
One of critical issues for high-energy high-current beam acceleration in ITER and JT-60SA is the high voltage holding which is dominated by vacuum discharges. The past results suggest that vacuum discharge occurs beyond the threshold of the dark current. The dark current can be derived from F-N theory where electric field enhancement factor beta is included. Though, beta could only be evaluated from the experiment previously. Therefore, the method to decide beta without experiment is required. This time dark currents were measured at three different areas to compare beta in different electric field. As a result, the effective electric field 
E, where E is average electric field, were found to be almost constant for different areas although the beta is largely different. By applying E, beta can be evaluated analytically, leading to the analytical prediction of the dark current and voltage holding capability without the measurements.
Hiratsuka, Junichi; Hanada, Masaya; Kojima, Atsushi; Umeda, Naotaka; Kashiwagi, Mieko; Miyamoto, Kenji*; Yoshida, Masafumi; Nishikiori, Ryo; Ichikawa, Masahiro; Watanabe, Kazuhiro; et al.
Review of Scientific Instruments, 87(2), p.02B137_1 - 02B137_3, 2016/02
Times Cited Count：4 Percentile：21.76(Instruments & Instrumentation)To understand the physics of the negative ion extraction/acceleration, the heat load density profile on the acceleration grid has been firstly measured in the ITER prototype accelerator where the negative ions are accelerated to 1 MeV with five acceleration stages. In order to clarify the profile, the peripheries around the apertures on the acceleration grid were separated into thermally insulated 34 blocks with thermocouples. The spatial resolution is as low as 3 mm and small enough to measure the tail of the beam profile with a beam diameter of 16 mm. It was found that there were two peaks of heat load density around the aperture. These two peaks were also clarified to be caused by the intercepted negative ions and secondary electrons from detailed investigation by changing the beam optics and gas density profile. This is the first experimental result, which is useful to understand the trajectories of these particles.
Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko; Umeda, Naotaka; Hiratsuka, Junichi; Ichikawa, Masahiro; Watanabe, Kazuhiro; Grisham, L. R.*; Tsumori, Katsuyoshi*; et al.
Review of Scientific Instruments, 87(2), p.02B144_1 - 02B144_4, 2016/02
Times Cited Count：9 Percentile：42.81(Instruments & Instrumentation)Time evolution of spatial profile of negative ion production during an initial conditioning phase has been experimentally investigated in the JT-60 negative ion source. Up to 0.4 g Cs injection, there is no enhancement of the negative ion production and no observation of the Cs emission signal in the source, suggesting the injected Cs is mainly deposited on the water-cooled wall near the nozzle. After 0.4 g Cs injection, enhancement of the negative ion production appeared only at the central segment of the PG. The calculation of the Cs neutral/ion trajectories implied that a part of Cs was ionized near the nozzle and was transported to this area. The expansion of the area of the surface production was saturated after ~2 g Cs injection corresponding to 6000 s discharge time. From the results, it is found that Cs ionization and its transport plays an important role for the negative ion production.
Kojima, Atsushi; Hanada, Masaya; Tobari, Hiroyuki; Nishikiori, Ryo; Hiratsuka, Junichi; Kashiwagi, Mieko; Umeda, Naotaka; Yoshida, Masafumi; Ichikawa, Masahiro; Watanabe, Kazuhiro; et al.
Review of Scientific Instruments, 87(2), p.02B304_1 - 02B304_5, 2016/02
Times Cited Count：11 Percentile：49.05(Instruments & Instrumentation)Optimization techniques of the vacuum insulation design have been developed in order to realize a reliable voltage holding capability of Multi-Aperture Multi-Grid accelerators for giant negative ion sources for nuclear fusion. In this method, the nested multilayer configuration of each acceleration stage in the MAMuG accelerator can be uniquely designed to satisfy the target voltage within given boundary conditions. The evaluation of the voltage holding capabilities of each acceleration stages were based on the past experimental results of the area effect and the multi-aperture effect on the voltage holding capability. Moreover, total voltage holding capability of multi-stage was estimated by taking the multi-stage effect into account, which was experimentally obtained in this time. In this experiment, the multi-stage effect appeared as the superposition of breakdown probabilities in each acceleration stage, which suggested that multi-stage effect can be considered as the voltage holding capability of the single acceleration gap having the total area and aperture. The analysis on the MAMuG accelerator for JT-60SA agreed with the past gap-scan experiments with an accuracy of less than 10% variation.
Hanada, Masaya; Kojima, Atsushi; Tobari, Hiroyuki; Nishikiori, Ryo; Hiratsuka, Junichi; Kashiwagi, Mieko; Umeda, Naotaka; Yoshida, Masafumi; Ichikawa, Masahiro; Watanabe, Kazuhiro; et al.
Review of Scientific Instruments, 87(2), p.02B322_1 - 02B322_4, 2016/02
Times Cited Count：11 Percentile：49.05(Instruments & Instrumentation)In International Thermo-nuclear Experimental Reactor (ITER) and JT-60 Super Advanced (JT-60 SA), the D
ion beams of 1 MeV, 40 A and 0.5 MeV, 22 A are required to produce 3600 s and 100 s for the neutral beam injection, respectively. In order to realize such as powerful D ion beams for long duration time, Japan Atomic Energy Agency (JAEA) has energetically developed cesium (Cs)-seeded negative ion sources (CsNIS) and electro-static multi-aperture and multi-stage accelerators (MAMuG accelerator) which are chosen as the reference design of ITER and JT-60 SA. In the development of the CsNIS, a 100s production of the H ion beam has been demonstrated with a beam current of 15 A by modifying the JT-60 negative ion source. At the higher current, the long pulse production of the negative ions has been tried by the mitigation of the arcing in the plasma inside the ion source. As for the long pulse acceleration of the negative ions in the MAMuG accelerator, the beam steering angle has been controlled to reduce the power loading of the acceleration grids A pulse duration time has been significantly extended from 0.4 s to 60 s at reasonable beam power for ITER requirement. The achieved pulse duration time is limited by the capacity of the power supplies in the test stand. In the range of 
60 s, there are no degradations of beam optics and voltage holding capability in the accelerator. It leads to the further extension of the pulse duration time at higher power density. This paper reports the latest results of development on the negative ion source and accelerator at JAEA.
Shinto, Katsuhiro; Ichikawa, Masahiro; Takahashi, Hiroki; Kondo, Keitaro; Kasugai, Atsushi; Gobin, R.*; Sen
e, F.*; Chauvin, N.*; Ayala, J.-M.*; Marqueta, A.*; et al.
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.493 - 495, 2015/09
Development of the prototype accelerator (LIPAc) for the engineering validation of the International Fusion Materials Irradiation Facility (IFMIF) which is an accelerator driven neutron source has been progressed at Rokkasho. The LIPAc is a deuteron linear accelerator consisting of an injector, a radio-frequency quadrupole (RFQ) linac and a superconducting linac. The objective of LIPAc is to produce a CW beam with the energy and current of 9 MeV and 125 mA, respectively. The injector was developed at CEA/Saclay and succeeded to produce CW proton and deuteron beams of 100 keV/140 mA by autumn 2012. After the test at CEA/Saclay, the injector was shipped to the International Fusion Energy Research Centre (IFERC) in Rokkasho, Aomori and started to reassemble from the end of 2013. It was successfully produced proton beams in November 2014 at Rokkasho. While the ion source conditioning was done, the beam test was progressed. In this paper, the present status of the LIPAc injector at Rokkasho with some experimental results will be presented.
-irradiationChiba, Etsuko*; Iizuka, Tomoko*; Ichikawa, Mariko*; Ukai, Mitsuko*; Kikuchi, Masahiro; Kobayashi, Yasuhiko
Hoshasen To Sangyo, (137), p.29 - 32, 2014/12
no abstracts in English
Shinto, Katsuhiro; Ichikawa, Masahiro; Takahashi, Yasuyuki*; Kubo, Takashi*; Tsutsumi, Kazuyoshi; Kikuchi, Takayuki; Kasugai, Atsushi; Sugimoto, Masayoshi; Gobin, R.*; Girardot, P.*; et al.
Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1009 - 1012, 2014/10
The prototype accelerator is being developed as an engineering validation for the International Fusion Materials Irradiation Facility (IFMIF) equipped with an accelerator-driven-type neutron source for developing fusion reactor materials. This prototype accelerator is a deuteron linear accelerator consisting of an injector, an RFQ, a superconducting linac and their auxiliaries. It aims to produce a CW D
beam with the energy and current of 9 MeV/125 mA. The injector test was completed at CEA/Saclay in 2012 for producing a CW H beam and a CW D beam with the energy and current of 100 keV/140 mA. After the beam test at CEA/Saclay, the injector was transported to the International Fusion Energy Research Centre (IFERC) located in Rokkasho, Aomori, Japan. In the end of 2013, installation of the injector was started at IFERC for the injector beam test beginning from summer 2014 in order to obtain better beam qualities to be satisfied with the injection and acceleration of the following accelerators. In this paper, some results of the injector beam test performed at CEA/Saclay and the status quo of the installation of the injector at IFERC are presented.
Uwaba, Tomoyuki; Ito, Masahiro*; Nemoto, Junichi*; Ichikawa, Shoichi; Katsuyama, Kozo
Journal of Nuclear Materials, 452(1-3), p.552 - 556, 2014/09
Times Cited Count：1 Percentile：8.88(Materials Science, Multidisciplinary)The BAMBOO code was verified by results for the out-of-pile bundle compression test with large diameter pin bundle deformation under the bundle-duct interaction (BDI) condition. The pin diameters of were 8.5 mm and 10.4 mm, which are targeted as preliminary fuel pin diameters for the upgraded core of the prototype FBR and for demonstration and commercial FBRs studied in the FaCT project. In the bundle compression test, bundle cross-sectional views were obtained from X-ray computer tomography (CT)images and local parameters of bundle deformation were measured by CT image analyses. In the verification, calculation results of bundle deformation obtained by the BAMBOO code analyses were compared with the experimental results from the CT image analyses. The comparison showed that the BAMBOO code reasonably predicts deformation of large diameter pin bundles under the BDI condition by assuming that pin bowing and cladding oval distortion are the major deformation mechanisms.
Maebara, Sunao; Antonio, P.*; Ichikawa, Masahiro; Takahashi, Hiroki; Suzuki, Hiromitsu; Sugimoto, Masayoshi
Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.561 - 563, 2014/06
no abstracts in English
Takahashi, Hiroki; Maebara, Sunao; Sakaki, Hironao; Ichikawa, Masahiro; Suzuki, Hiromitsu; Sugimoto, Masayoshi
Progress in Nuclear Science and Technology (Internet), 4, p.261 - 263, 2014/04
An development of accelerator-based neutron irradiation facility is planning to develop materials for a demonstration fusion reactor. To obtain a 14 MeV neutron energy using the neutron-generating D-Li stripping reaction, an injection into liquid lithium flow by a 40 MeV deuteron beam is employed in IFMIF design concept. In the acceleration of deuteron beam, the activation due to the beam loss is critical issue. The activation analyses for the air in an accelerator vault are carried out by PHITS code and DCHAIN code using the experimental data for deuteron induced thick target neutron yield at 5 MeV and 9 MeV for source term.
Maebara, Sunao; Palmieri, A.*; Mereu, P.*; Ichikawa, Masahiro; Takahashi, Hiroki; Comunian, M.*; Suzuki, Hiromitsu; Pisent, A.*; Sugimoto, Masayoshi
Fusion Engineering and Design, 88(9-10), p.2740 - 2743, 2013/10
Times Cited Count：3 Percentile：25.73(Nuclear Science & Technology)Maebara, Sunao; Ichikawa, Masahiro
Proceedings of 3rd International Particle Accelerator Conference (IPAC '12) (Internet), p.3284 - 3286, 2013/07
Maebara, Sunao; Ichikawa, Masahiro; Palmieri, A.*
Proceedings of 3rd International Particle Accelerator Conference (IPAC '12) (Internet), p.3287 - 3289, 2012/09
Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ichikawa, Yasuo*; Nakamura, Masaru*
JAEA-Research 2010-066, 20 Pages, 2011/03
JAEA-Research-2010-066.pdf:2.26MB
In the safety assessment for a geological disposal of radioactive waste, it is important to establish modelling methods and validation methods for regional groundwater flow system in the depth of 300
1000m to estimate radionuclide migration to human environment through groundwater flow system. The study discussed application of data and assessment methods for model validation based on multiple indicators such as hydrology, groundwater chemistry, temperature and age of groundwater in case of the Boso Peninsula in Chiba Prefecture where a lot of in-situ data about groundwater was measured. This results show that existing hydrochemical and thermal data are applicable to explain freshwater and saltwater distribution and groundwater flow pattern in case of regional scale. It also indicates that gravitational groundwater is likely to flow into the deep part of fresh-saltwater interface based on the exist of Na-HCO
type water above fresh-saltwater interface mixed with meteoric water and that multiple indicators are applicable to evaluate groundwater flow property and groundwater flow boundary in case of site scale region.
-raysKobayashi, Yasuhiko; Kikuchi, Masahiro; Todoriki, Setsuko*; Saito, Kimie*; Katsura, Yoko*; Kameya, Hiromi*; Ichikawa, Mariko*; Iizuka, Tomoko*; Chiba, Etsuko*; Ukai, Mitsuko*
Shokuhin Shosha, 45(1-2), p.26 - 33, 2010/09
Effect of -irradiation on sprouting and rooting of garlic was investigated. Sprouting and rooting of garlic were inhibited by irradiation of bulbs at 2 months after harvest with doses more than 30 Gy. Four weeks-later irradiation requires higher doses to complete sprouting/rooting inhibition.
Li, T.*; Garg, U.*; Liu, Y.*; Marks, R.*; Nayak, B. K.*; Madhusudhana Rao, P. V.*; Fujiwara, Mamoru*; Hashimoto, Hisanobu*; Nakanishi, Kosuke*; Okumura, Shun*; et al.
Physical Review C, 81(3), p.034309_1 - 034309_11, 2010/03
Times Cited Count：107 Percentile：97.48(Physics, Nuclear)Ueno, Fumiyoshi; Kato, Chiaki; Motooka, Takafumi; Ichikawa, Shiro*; Yamamoto, Masahiro
Journal of Nuclear Science and Technology, 45(10), p.1091 - 1097, 2008/10
Times Cited Count：11 Percentile：59.16(Nuclear Science & Technology)For purpose of life prediction of components in spent nuclear fuel reprocessing plants, corrosion test was performed about 36,000 hours using a large scale mock-up test apparatus of a reduced pressurized thermosiphon evaporator, and a corrosion mechanism of heat transfer tube made of an ultra-low carbon type 304 stainless steel in boiling nitric acid solution was studied. As the results, the tendencies of increases of amount of corrosion and corrosion rate were saturated when intergranular penetration and grain dropping occurred in turn. This result means that a linear estimation can be applied to the life prediction for corrosion. No difference in morphologies of intergranular corrosion existed among three portions could find even though amounts of corrosion were different. The amount of corrosion was dominated by tube surface temperature and heat flux. And the largest amount of corrosion could be seen at boiling starting portion and the top where indicated highest values of tube surface temperatures.
