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Journal Articles

Benchmark analysis by Beremin model and GTN model in CAF subcommittee

Hirota, Takatoshi*; Nagoshi, Yasuto*; Hojo, Kiminobu*; Okada, Hiroshi*; Takahashi, Akiyuki*; Katsuyama, Jinya; Ueda, Takashi*; Ogawa, Takuya*; Yashirodai, Kenji*; Ohata, Mitsuru*; et al.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 9 Pages, 2021/07

Journal Articles

Grain size dependence of meteoric $$^{10}$$Be concentrations in bed-sediments of Ado and Yasu rivers flowing into Lake Biwa

Fujisawa, Jumpei*; Minami, Masayo*; Kokubu, Yoko; Matsuzaki, Hiroyuki*

JAEA-Conf 2018-002, p.91 - 94, 2019/02

Beryllium-10 ($$^{10}$$Be) of a cosmogenic nuclide precipitates in forms of BeO and Be(OH)$$_{2}$$ attaching with aerosol on the Earth surface. It is accumulated on the sea- and lake-bottoms. Recently, the meteoric $$^{10}$$Be is attracting attention as a powerful tool for investigating the past climate change, because it is affected by the earth- and lorcal- cyclical changes of materials such as atmosphere and water circulation. The $$^{10}$$Be exists mostly as hydroxide at pH $$>$$5, and is easy to adhere to soil and mineral surface. Therefore, $$^{10}$$Be concentration in sediment could be influenced by its grain size composition because fine-grained sediment has a big surface area per unit mass. The purpose of this study is to reveal the relationship between $$^{10}$$Be concentrations and the grain-size of river sediments. The samples used were bottom-sediments of 18 rivers flowing into Lake Biwa, Japan. The sediments were sieved to 5 fractions and analyzed each for $$^{10}$$Be concentration by JAEA-AMS-TONO.

Journal Articles

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

 Times Cited Count:17 Percentile:88.2(Materials Science, Multidisciplinary)

Journal Articles

Precise determination of $$^{12}_{Lambda}$$C level structure by $$gamma$$-ray spectroscopy

Hosomi, Kenji; Ma, Y.*; Ajimura, Shuhei*; Aoki, Kanae*; Dairaku, Seishi*; Fu, Y.*; Fujioka, Hiroyuki*; Futatsukawa, Kenta*; Imoto, Wataru*; Kakiguchi, Yutaka*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2015(8), p.081D01_1 - 081D01_8, 2015/08

 Times Cited Count:13 Percentile:70.14(Physics, Multidisciplinary)

Level structure of the $$^{12}_{Lambda}$$C hypernucleus was precisely determined by means of $$gamma$$-ray spectroscopy. We identified four $$gamma$$-ray transitions via the $$^{12}$$C$$(pi^{+},K^{+}gamma)$$ reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet $$(2^{-}, 1^{-}_{1})$$ was measured to be $$161.5pm0.3$$(stat)$$pm0.3$$ (syst)keV from the direct $$M1$$ transition. Excitation energies of the $$1^{-}_{2}$$ and $$1^{-}_{3}$$ states were measured to be $$2832pm3pm4$$, keV and $$6050pm8pm7$$, keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of $$Lambda$$ hypernuclei.

Journal Articles

Nitrogen K-edge X-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

Shimada, Hiroyuki*; Minami, Hirotake*; Okuizumi, Naoto*; Sakuma, Ichiro*; Ukai, Masatoshi*; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro*; Saito, Yuji

Journal of Chemical Physics, 142(17), p.175102_1 - 175102_9, 2015/05


 Times Cited Count:10 Percentile:46.84(Chemistry, Physical)

Journal Articles

High spatial resolution ZnO scintillator for an in situ imaging device in EUV region

Arita, Ren*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Empizo, M.*; Hori, Tatsuhiro*; Fukuda, Kazuhito*; Minami, Yuki*; Sarukura, Nobuhiko*; Maruyama, Momoko; et al.

Optical Materials, 36(12), p.2012 - 2015, 2014/10

 Times Cited Count:7 Percentile:38.97(Materials Science, Multidisciplinary)

A single shot image of a ZnO crystal excited by the EUV laser of Kansai Photon Science Institute was captured. The evaluated EUV beam waist radii from the ZnO emission pattern along the horizontal and vertical axes are 5.0 and 4.7$$mu$$m, respectively. The expected focal spot size of EUV laser and the spatial resolution of the magnifier (including the Schwarzschild objectives and lenses) are however 1 and 4$$mu$$m, respectively. The discrepancy on the spatial resolutions is attributed to exciton diffusion. We estimated the ZnO exciton diffusion length from the effective decay time which is shortened by exciton-exciton collision quenching and which is dependence on excitation energy density. Our results indicate that the short lifetime of ZnO is required to improve the spatial resolution.

Journal Articles

Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

Shimada, Hiroyuki*; Fukao, Taishi*; Minami, Hirotake*; Ukai, Masatoshi*; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro*; Saito, Yuji

Journal of Chemical Physics, 141(5), p.055102_1 - 055102_8, 2014/08

 Times Cited Count:14 Percentile:55.9(Chemistry, Physical)

Journal Articles

Structural changes of nucleic acid base in aqueous solution as observed in X-ray absorption near edge structure (XANES)

Shimada, Hiroyuki*; Fukao, Taishi*; Minami, Hirotake*; Ukai, Masatoshi*; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro*; Saito, Yuji

Chemical Physics Letters, 591, p.137 - 141, 2014/01

 Times Cited Count:8 Percentile:35.49(Chemistry, Physical)

Journal Articles

Long-term stability of fracture systems and their behaviour as flow paths in uplifting granitic rocks from the Japanese orogenic field

Yoshida, Hidekazu*; Metcalfe, R.*; Ishibashi, Masayuki; Minami, Masayo*

Geofluids, 13(1), p.45 - 55, 2013/02

 Times Cited Count:14 Percentile:63.37(Geochemistry & Geophysics)

In granitic rocks fracture networks provide pathways for groundwater flow and solute transport that need to be understood to assess the long-term performance of deep underground environment. In order to clarify the long-term processes, Japanese plutons of different ages were studied. Detailed investigation of in-situ fracture fillings sampled from a depth of 300 meters was carried out to clarify the fracturing and mineral infilling processes. Different plutons show identical episodes, consisting of: brittle tensile fracturing (Stage I); relatively rapid uplifting accompanied by hydrothermal water circulation that produced fracture fillings (Stage II); and a period of low-temperature meteoric water circulation (Stage III). The paragenesis of carbon isotopic compositions of carbonate minerals show that there were distinct episodes of mineral precipitation. The evolution of fillings identified here enable development of a model of fracturing and persistence of fluid conducting systems.

Journal Articles

Evaluation of soft X-ray laser with ${it in situ}$ imaging device of high spatial resolution ZnO scintillator

Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Takeda, Kohei*; Nishi, Ryosuke*; Minami, Yuki*; Cadatal-Raduban, M.*; Sarukura, Nobuhiko*; Nishimura, Hiroaki*; et al.

Japanese Journal of Applied Physics, 50(12), p.122202_1 - 122202_4, 2011/12

 Times Cited Count:8 Percentile:37.66(Physics, Applied)

We demonstrate the potential of a hydrothermal method-grown ZnO as a high-spatial resolution imaging device for in-situ soft X-ray laser diagnostics by characterizing the exciton emission patterns. By plotting the emission pattern radii at each position, we estimated the evolution of the beam radius around the focal point. The beam profile of the Ni-like Ag ion plasma laser was estimated from the waist radii as 29 and 21$$mu$$m, the divergence angle as 7.2 and 11 mrad and the M2 factor as 47 and 50 in the horizontal- and vertical-axis, respectively. Spatial resolution of the magnifier was estimated to be 6$$mu$$m and is expected to improve by optimizing the optics of the magnifier and using a telescope. Our results would enhance the use of ZnO as an imaging device that would play a crucial role in the development and application of soft X-ray light sources.

Journal Articles

Development of 28 GHz and 77 GHz 1 MW gyrotron for ECRH of magnetically confined plasma

Kariya, Tsuyoshi*; Minami, Ryutaro*; Imai, Tsuyoshi*; Sakamoto, Keishi; Kubo, Shin*; Shimozuma, Takashi*; Takahashi, Hiromi*; Ito, Satoshi*; Muto, Takashi*; Mitsunaka, Yoshika*; et al.

Fusion Science and Technology, 55(2T), p.91 - 94, 2009/02

 Times Cited Count:11 Percentile:63.13(Nuclear Science & Technology)

JAEA Reports

Analysis of the characteristics of AE wave using boring core of sedimentary soft rock and study on the field measurement of AE for the evaluation of EDZ (Joint research)

Aoki, Kenji*; Mito, Yoshitada*; Minami, Masayuki*; Matsui, Hiroya; Niunoya, Sumio*

JAEA-Research 2007-077, 126 Pages, 2007/09


To understand the size and state of EDZ is one of the problems in the technological development for geological disposal of HLW. AE which is measured directly and evaluate EDZ is paid to attention inside and outside the country, and the utility is reported for the crystalline rock. However, there are few cases to measure AE in sedimentary soft rocks because of the difficulty to acknowledge a few AE waves with small energy. The author consulted AE properties of Horonobe siliceous rocks from laboratory tests and evaluated size and state of EDZ from numerical analysis.

Journal Articles

Evaluation of fracturing process of soft rocks at great depth by AE measurement and DEM simulation

Mito, Yoshitada*; Chang, C. S.*; Aoki, Kenji*; Matsui, Hiroya; Niunoya, Sumio; Minami, Masayuki*

Proceedings of 11th Congress of the International Society for Rock Mechanics (ISRM 2007), Vol.1, p.273 - 276, 2007/08

In order to examine the relationship between AE, stress change and rock failure, the authors conducted the high stiffness triaxial compression tests including AE measurements, and its simulations by DEM (Distinct Element Method) using the bonded particle model. As the result, it is clarified that predominant AE frequency is a significant AE parameters to monitor the stress change in fracturing process of soft sedimentary rocks. After that, the DEM simulation of the triaxial compression test using the bonded particles model is conducted to visualize the fracturing process in the rock specimen. As the results, the relationship between AE, stress change and rock failure is clarified. Furthermore the three-dimensional DEM simulation under the in-situ stress condition provides a successful result to examine the borehole breakout observed in the actual deep borehole in the soft sedimentary rock, and the applicability of the simulation to the actual field is verified.

Journal Articles

Achievement of robust high-efficiency 1 MW oscillation in the hard-self-excitation region by a 170 GHz continuous-wave gyrotron

Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Minami, Ryutaro*; Kobayashi, Noriyuki; Kajiwara, Ken

Nature Physics, 3(6), p.411 - 414, 2007/06

 Times Cited Count:186 Percentile:97.57(Physics, Multidisciplinary)

The first 1 MW quasi-continuous wave generation is demonstrated at 170 GHz gyrotron of TE31,8 resonator mode with outstanding efficiency of greater than 55 percent. The robust high efficiency oscillation is obtained in a hard self-excitation region with an active control of gyrotron parameters. Furthermore, a novel nonlinear process is found that the desired TE31,8 mode is excited as a parasitic mode of an adjacent TE30,8 mode and finally the TE31,8 dominates a system. This effect extends a substantial soft self-excitation region of the desired mode significantly.

Journal Articles

Development of the 170GHz gyrotron and equatorial launcher for ITER

Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Minami, Ryutaro*; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Kobayashi, Noriyuki

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

no abstracts in English

Journal Articles

High power and high efficiency operation of 170GHz gyrotron

Kasugai, Atsushi; Minami, Ryutaro*; Takahashi, Koji; Kobayashi, Noriyuki; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Sakamoto, Keishi

Fusion Science and Technology, 51(2T), p.213 - 216, 2007/02

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Evaluation of fracturing process of soft rocks at great depth by AE measurement and DEM simulation

Aoki, Kenji*; Mito, Yoshitada*; Kurokawa, Susumu*; Matsui, Hiroya; Niunoya, Sumio; Minami, Masayuki*

Dai-36-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu, p.235 - 238, 2007/01

The monitoring of EDZ (Excavation Disturbed Zone) is one of the most important required technologies for the design of rock caverns such as the high-level radioactive waste repository. The authors developed the stress-based evaluation system of EDZ by AE monitoring and DEM (Distinct Element Method) simulation. In order to apply this system to the soft rock site, the authors try to grasp the relationship between AE parameters, stress change and rock failure by performing the high stiffness tri-axial compression tests including AE measurements on the soft rock samples, and its simulations by DEM using bonded particle model.

Journal Articles

Interoperability establishment between two different GRIDs

Kushida, Noriyuki; Suzuki, Yoshio; Minami, Takahiro; Aoyagi, Tetsuo; Nakajima, Norihiro

Zen NEC C&C Shisutemu Yuzakai Heisei-19-Nendo Rombunshu (CD-ROM), 10 Pages, 2007/00

Interoperability establishment between two different GRIDs.

Journal Articles

Long pulse operation of 170 GHz ITER gyrotron by beam current control

Kasugai, Atsushi; Minami, Ryutaro; Takahashi, Koji; Kobayashi, Noriyuki; Sakamoto, Keishi

Fusion Engineering and Design, 81(23-24), p.2791 - 2796, 2006/11

 Times Cited Count:9 Percentile:56.05(Nuclear Science & Technology)

In JAEA (Japan Atomic Energy Agency, formerly JAERI), development of 170 GHz, 1 MW, CW gyrotron for ITER has been carried out. Key technologies for ITER gyrotron such as a diamond window, a depressed collector for high efficiency operation and a stable operation at 170 GHz/1 MW with higher mode TE31,8 have been developed. By integration of these key technologies, gyrotron performance of 0.5 MW/ 100 sec and 0.9 MW/ 9.2 sec were demonstrated. Hence, next target is a demonstration of long pulse operation. One of the issues which prevent the pulse extension is large beam current decrease due to so called the emission cooling of a cathode. During the operation, the oscillation mode shift from TE31,8 to TE30,8 was caused by the current decrease. Then, the magnetic field of the cavity should be increased to avoid the downshift of the oscillation mode, however, the efficiency decreases and the parasitic oscillation appears in a quasi-optical mode converter. To suppress the beam current decrease and to demonstrate the long pulse operation of the high power gyrotron, pre-programming control of the cathode heater power was applied and the long pulse experiment was carried out to sustain the beam current. As a result, stable electron beam of 1000 s, which is required for ITER operation, was demonstrated without oscillation, and pre-programming control directed the effectiveness for constant beam current. Moreover, in the experiment of the long pulse oscillation with oscillation, the pre-programming control suppressed the beam current decrease. Up to now, stable long pulse operation of $$sim$$8 minutes with 0.2 MW output power was obtained. The output energy of the oscillation is maximum value in the 170GHz ITER gyrotron. Since overheating due to stray radiation inside the gyrotron limit the pulse extension, long pulse operation with high power output will be achieved by enhancement of the cooling and reduction of stray radiation due to modification of a built-in mode converter.

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