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Rajeev, H. S.*; Hu, X.*; Chen, W.-L.*; Zhang, D.*; Chen, T.*; Kofu, Maiko*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Chen, A. Z.*; Johnson, G. C.*; et al.
Journal of the Physical Society of Japan, 94(3), p.034602_1 - 034602_14, 2025/03
Jin, H.*; Choi, E. S.*; Wu, H.-C.*; Curro, N. J.*; Nawa, Kazuhiro*; Sato, Taku*; Kiyanagi, Ryoji; Ohara, Takashi; Klavins, P.*; Taufour, V.*
Physical Review B, 111(3), p.035103_1 - 035103_7, 2025/01
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.
JAEA-Technology 2024-003, 17 Pages, 2024/06
JAEA-Technology-2024-003.pdf:1.91MB
In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.
Hasegawa, Toshinari; Nagasumi, Satoru; Nemoto, Takahiro; Nakajima, Kunihiro; Yokoyama, Keisuke; Fujiwara, Yusuke; Arakawa, Ryoki; Iigaki, Kazuhiko; Inoi, Hiroyuki; Kawamoto, Taiki
Proceedings of 2024 International Congress on Advanced in Nuclear Power Plants (ICAPP 2024) (Internet), 10 Pages, 2024/06
The filter element of the primary gas circulators (PGC) in High Temperature engineering Test Reactor (HTTR) and its deposits were investigated by Scanning Electron Microscope (SEM) observation and Energy Dispersive X-ray spectroscopy (EDX) analysis to find the cause of the increase of the filter differential pressure during the operation in 2021. SEM observation showed that the clumpy deposits and fibrous deposits smaller than the filtration pore size and the rod-shaped deposits larger than the pore size were present on the filter element. EDX analysis showed that the clumpy deposits and fibrous deposits could include silicone oil in the primary helium purification system (PHPS) gas circulators and that the rod-shaped deposits were thermal insulators inside of the co-axial double pipes in the primary cooling system. It is considered that silicone oil leaked from the PHPS gas circulators due to deterioration in the absorption performance of the activated charcoal filter. Next, it could be vaporized and reach PGC's filter element after passing through the reactor core. Since those deposits including silicone oil were present over the entire surface of the filter element, the filter differential pressure could be increased due to a reduction in the pore size and a rise in its flow resistance. The thermal insulator was unrelated to filter clogging because it was present mainly in the lower part of the filter element. Therefore, silicone oil could increase the filter differential pressure, and the graphite powder, which is the cause of the previous issue was unrelated.
He spin filter and small-angle X-ray scatteringRyoki, Akiyuki*; Watanabe, Fumi*; Okudaira, Takuya*; Takahashi, Shingo*; Oku, Takayuki; Hiroi, Kosuke; Motokawa, Ryuhei; Nakamura, Yo*
Journal of Chemical Physics, 160(11), p.114907_1 - 114907_9, 2024/03
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.
JAEA-Technology 2023-005, 33 Pages, 2023/05
JAEA-Technology-2023-005.pdf:5.25MB
During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.
Oishi, Kazuki*; Igarashi, Daisuke*; Tatara, Ryoichi*; Kawamura, Yukihiko*; Hiroi, Kosuke; Suzuki, Junichi*; Umegaki, Izumi*; Nishimura, Shoichiro*; Koda, Akihiro*; Komaba, Shinichi*; et al.
Journal of Physics; Conference Series, 2462, p.012048_1 - 012048_5, 2023/03
Times Cited Count：0 Percentile：0.00(Physics, Applied)Kurita, Keisuke; Sakai, Takuro; Suzui, Nobuo*; Yin, Y.-G.*; Sugita, Ryohei*; Kobayashi, Natsuko*; Tanoi, Keitaro*; Kawachi, Naoki*
Japanese Journal of Applied Physics, 60(11), p.116501_1 - 116501_4, 2021/11
Times Cited Count：2 Percentile：11.79(Physics, Applied)Radioisotope tracer imaging is useful for studying plant physiological phenomena. In this study, we developed an autoradiography system with phosphor powder (ZnS:Ag), "Live-autoradiography", for imaging radioisotope dynamics in a living plant. This system visualizes the element migration and accumulation in intact plants continuously under a light environment. An imaging test was performed on point sources of 
Cs, with a radioactivity of 10-100 kBq of being observed; this indicates satisfactory system linearity between the image intensity and the radioactivity of Cs. Moreover, dynamics imaging of Cs was performed on an intact soybean plant for four days. The serial images indicated Cs accumulation in the node, vein, and growing point of the plant. The developed system can be used for studying plant physiological phenomena and can be employed for quantitative measurement of radionuclides.
Okuma, Ryutaro*; Kofu, Maiko; Asai, Shinichiro*; Avdeev, M.*; Koda, Akihiro*; Okabe, Hirotaka*; Hiraishi, Masatoshi*; Takeshita, Soshi*; Kojima, Kenji*; Kadono, Ryosuke*; et al.
Nature Communications (Internet), 12, p.4382_1 - 4382_7, 2021/07
Times Cited Count：8 Percentile：60.40(Multidisciplinary Sciences)
GeP
S
Yajima, Takeshi*; Hinuma, Yoyo*; Hori, Satoshi*; Iwasaki, Rui*; Kanno, Ryoji*; Ohara, Takashi; Nakao, Akiko*; Munakata, Koji*; Hiroi, Zenji*
Journal of Materials Chemistry A, 9(18), p.11278 - 11284, 2021/05
Times Cited Count：29 Percentile：81.66(Chemistry, Physical)Kitamura, Ryo; Bae, S.*; Choi, S.*; Fukao, Yoshinori*; Iinuma, Hiromi*; Ishida, Katsuhiko*; Kawamura, Naritoshi*; Kim, B.*; Kondo, Yasuhiro; Mibe, Tsutomu*; et al.
Physical Review Accelerators and Beams (Internet), 24(3), p.033403_1 - 033403_9, 2021/03
Times Cited Count：2 Percentile：26.88(Physics, Nuclear)A negative muonium ion (Mu
) source using an aluminum foil target was developed as a low-energy muon source. An experiment to produce Mu ions was conducted to evaluate the performance of the Mu ion source. The measured event rate of Mu ions was 
Mu/s when the event rate of the incident muon beam was 
/s. The formation probability, defined as the ratio of the Mu ions to the incident muons on the Al target, was 
. This Mu ion source boosted the development of the muon accelerator, and the practicality of this low-energy muon source obtained using a relatively simple apparatus was demonstrated.
Nagae, Daisuke*; Abe, Yasushi*; Okada, Shunsuke*; Omika, Shuichiro*; Wakayama, Kiyoshi*; Hosoi, Shun*; Suzuki, Shinji*; Moriguchi, Tetsuro*; Amano, Masamichi*; Kamioka, Daiki*; et al.
Nuclear Instruments and Methods in Physics Research A, 986, p.164713_1 - 164713_7, 2021/01
Times Cited Count：8 Percentile：70.50(Instruments & Instrumentation)Kubota, Tomohiro; Kuroda, Hisao*; Watanabe, Mirai*; Takahashi, Akiko*; Nakazato, Ryoji*; Tarui, Mika*; Matsumoto, Shunichi*; Nakagawa, Keita*; Numata, Yasuko*; Ouchi, Takao*; et al.
Atmospheric Environment, 243, p.117856_1 - 117856_9, 2020/12
Times Cited Count：3 Percentile：11.72(Environmental Sciences)The dry and wet depositions of atmospheric ammonia (NH) is one of the important pathways of nitrogen loads to aquatic ecosystems. Crop and livestock agriculture, one of the largest emitters of NH in Asian countries, are known to cause high spatial and seasonal variation of NH and influence the surrounding lake basin areas via its dry and wet deposition. However, the spatial characteristics of the NH concentration in basin scale are not completely understood for regulation in NH emission. Here we aim to clarify dominant factors of spatial and seasonal variations of the NH concentration in a eutrophic lake basin surrounded by agricultural areas in Japan. Passive sampling over various land use categories in the basin was conducted at 36 sites in total from October 2018 to January 2020. Interestingly, the observed NH concentration near the livestock houses were higher in winter than summer, which was inconsistent with knowledge of seasonal changes of current NH emission inventory based on temperature-driven volatilization process. Comparing monthly NH concentrations with various meteorological factors, we suggested the importance of seasonal advection of NH from high emission sources to which has been rarely paid attention by the previous past studies. As for this, should be considered for lake ecosystem management since deposition of NH is known to be closely related to the ecological processes such as phytoplankton blooming.
Zhang, D.*; Hu, X.*; Chen, T.*; Abernathy, D. L.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Kofu, Maiko; Foley, B. J.*; Yoon, M.*; Choi, J. J.*; et al.
Physical Review B, 102(22), p.224310_1 - 224310_10, 2020/12
Times Cited Count：6 Percentile：31.78(Materials Science, Multidisciplinary)
anisotropic triangular antiferromagnet CaReO
ClNawa, Kazuhiro*; Hirai, Daigoro*; Kofu, Maiko; Nakajima, Kenji; Murasaki, Ryo*; Kogane, Satoshi*; Kimata, Motoi*; Nojiri, Hiroyuki*; Hiroi, Zenji*; Sato, Taku*
Physical Review Research (Internet), 2(4), p.043121_1 - 043121_11, 2020/12
The spin excitations of the 
= anisotropic triangular antiferromagnet CaReOCl were investigated by inelastic neutron-scattering experiments. The spin excitation spectrum exhibits sharp dispersive modes in addition to a spinonlike continuum. The consistency with the simulated spectrum based on the random-phase approximation is better for CaReOCl than for CsCuCl
, indicating that the spin system in the former remains closer to a Tomonaga-Luttinger liquidlike disordered state.
Nakazawa, Yuga*; Bae, S.*; Choi, H.*; Choi, S.*; Iijima, Toru*; Iinuma, Hiromi*; Kawamura, Naritoshi*; Kitamura, Ryo; Kim, B.*; Ko, H. S.*; et al.
Nuclear Instruments and Methods in Physics Research A, 937, p.164 - 167, 2019/09
Times Cited Count：3 Percentile：20.86(Instruments & Instrumentation)A muon linac is under development for the precise measurement of the muon anomalous magnetic moment (
-2) and electric dipole moment (EDM) with a reaccelerated thermal muon beam. An H
source driven by an ultraviolet light has been developed for the muon acceleration experiment. Prior to the acceleration experiment, a beamline commissioning was performed using this H beam, since the accelerated muon intensity is very low. We successfully measured the magnetic rigidity, which is essential for identifying the accelerated muons. This H source is capable of utilizing as a general-purpose beam source for other beamline.
Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.
EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01
Times Cited Count：13 Percentile：98.48(Quantum Science & Technology)Oikawa, Kenichi; Su, Y. H.; Kiyanagi, Ryoji; Kawasaki, Takuro; Shinohara, Takenao; Kai, Tetsuya; Hiroi, Kosuke; Harjo, S.; Parker, J. D.*; Matsumoto, Yoshihiro*; et al.
Physica B; Condensed Matter, 551, p.436 - 442, 2018/12
Times Cited Count：6 Percentile：27.38(Physics, Condensed Matter)Otani, Masashi*; Sue, Yuki*; Fukao, Yoshinori*; Futatsukawa, Kenta*; Kawamura, Naritoshi*; Mibe, Tsutomu*; Miyake, Yasuhiro*; Shimomura, Koichiro*; Yamazaki, Takayuki*; Iijima, Toru*; et al.
Journal of Physics; Conference Series, 1067(5), p.052012_1 - 052012_7, 2018/09
Times Cited Count：1 Percentile：45.40(Physics, Particles & Fields)We have measured the muon beam profile after acceleration using a radio frequency quadrupole linac (RFQ). Positive muons are injected to an aluminum degrader and negative muoniums (Mu) are generated. The generated Mus are extracted by an electrostatic lens and accelerated to 89 keV by the RFQ. The accelerated Mus are transported to a beam profile monitor (BPM) through a quadrupole magnet pair and a bending magnet. The BPM consists of a micro-channel plate, a phospher screen, and a CCD camera. Measured profile in the vertical direction is consistent to the simulation. This profile measurement is one of milestones for realizing a muon linac for measurement of the muon anomalous magnetic moment at the Japan Proton Accelerator Research Complex.
Kim, B.*; Bae, S.*; Choi, H.*; Choi, S.*; Kawamura, Naritoshi*; Kitamura, Ryo*; Ko, H. S.*; Kondo, Yasuhiro; Mibe, Tsutomu*; Otani, Masashi*; et al.
Nuclear Instruments and Methods in Physics Research A, 899, p.22 - 27, 2018/08
Times Cited Count：7 Percentile：53.34(Instruments & Instrumentation)A beam profile monitor (BPM) based on a microchannel plate has been developed for muon beams with low transverse momentum for the measurement of the muon anomalous magnetic moment and electric dipole moment at high precision, with capability of diagnosing muon beams of kinetic energy range from a few keV to 4 MeV. The performance of the BPM has been evaluated using a surface muon beam at J-PARC and additionally with an ultraviolet (UV) light source. It has been confirmed that the BPM has a dynamic range from a few to 10
muons per bunch without saturation. The spatial resolution of the BPM has been estimated to be less than 0.30 mm. The positron background from muon decays is an obstacle in muon beam profile monitoring and a partial discrimination of the positrons has been achieved under discrete particle conditions.
