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Journal Articles

Simultaneous sequestration of Co$$^{2+}$$ and Mn$$^{2+}$$ by fungal manganese oxide through asbolane formation

Aoshima, Miku*; Tani, Yukinori*; Fujita, Rina*; Tanaka, Kazuya; Miyata, Naoyuki*; Umezawa, Kazuhiro*

Minerals (Internet), 12(3), p.358_1 - 358_16, 2022/03

 Times Cited Count:4 Percentile:85.88(Geochemistry & Geophysics)

In this study, we conducted sequestration experiments of Co$$^{2+}$$ by ${it Acremonium strictum}$ KR21-2 in a Mn$$^{2+}$$/Co$$^{2+}$$ binary solution at pH7. The sequestration of Co$$^{2+}$$ by newly formed BMOs readily progressed in parallel with the exogenous Mn$$^{2+}$$, with higher efficiency than that in single Co$$^{2+}$$ solutions. This is attributed to a synergetic effect on Co$$^{2+}$$ sequestration through the formation of asbolane in Mn$$^{2+}$$/Co$$^{2+}$$ binary systems.

JAEA Reports

Manufacture of substitutive assemblies for MONJU reactor decommissioning

Sakakibara, Hiroshi; Aoki, Nobuhiro; Muto, Masahiro; Otabe, Jun; Takahashi, Kenji*; Fujita, Naoyuki*; Hiyama, Kazuhiko*; Suzuki, Hirokazu*; Kamogawa, Toshiyuki*; Yokosuka, Toru*; et al.

JAEA-Technology 2020-020, 73 Pages, 2021/03


The decommissioning is currently in progress at the prototype fast breeder reactor Monju. Fuel assemblies will be taken out of its core for the first step of the great task. Fuel assemblies stand on their own spike plugged into a socket on the core support plate and support with adjacent assemblies through their housing pads each other, resulting in steady core structure. For this reason, some substitutive assemblies are necessary for the purpose of discharging the fuel assemblies of the core. Monju side commissioned, therefore, Plutonium Fuel Development Center to manufacture the substitutive assemblies and the Center accepted it. This report gives descriptions of design, manufacture, and shipment in regard to the substitutive assemblies.

Journal Articles

Hydrogen isotope effects on ITG scale length, pedestal and confinement in JT-60 H-mode plasmas

Urano, Hajime; Takizuka, Tomonori*; Aiba, Nobuyuki; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Nuclear Fusion, 53(8), p.083003_1 - 083003_8, 2013/08

 Times Cited Count:26 Percentile:76.83(Physics, Fluids & Plasmas)

Dependence of heat transport, edge pedestal and confinement on isotopic composition was investigated in conventional H-mode plasmas. Identical profiles for the electron density, electron temperature, and ion temperature were obtained for hydrogen and deuterium plasmas, whereas the required power clearly increased for hydrogen, which resulted in reduction of heat diffusivity for deuterium. The inverse of the ion-temperature-gradient (ITG) scale length which is required for a given ion heat diffusivity increased by a factor of approximately 1.2 for deuterium compared with that for hydrogen.

Journal Articles

Dependence of heat transport and confinement on isotopic composition in conventional H-mode plasmas in JT-60U

Urano, Hajime; Takizuka, Tomonori*; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/01

Dependence of heat transport on isotopic composition is investigated in conventional H-mode plasmas for the application to ITER. The identical profiles of $$n_mathrm{e}$$, $$T_mathrm{e}$$ and $$T_mathrm{i}$$ are obtained for hydrogen and deuterium plasmas while the required power becomes clearly larger for hydrogen, resulting in the reduction of the heat diffusivity for deuterium. The result of the identical temperature profiles in spite of different heating power suggests that the characteristics of heat conduction differs essentially between hydrogen and deuterium even at the same scale length of temperature gradient. On the other hand, the edge stability is improved by increased total $$beta_mathrm{p}$$ regardless of the difference of the isotropic composition.

Journal Articles

Energy confinement of hydrogen and deuterium H-mode plasmas in JT-60U

Urano, Hajime; Takizuka, Tomonori*; Fujita, Takaaki; Kamada, Yutaka; Nakano, Tomohide; Oyama, Naoyuki; JT-60 Team

Nuclear Fusion, 52(11), p.114021_1 - 114021_10, 2012/11

 Times Cited Count:19 Percentile:64.54(Physics, Fluids & Plasmas)

Energy confinement properties for hydrogen and deuterium H-mode plasmas are investigated. The stored energy for deuterium becomes larger approximately by a factor of 1.7-2.0 than that for hydrogen at a given heating power. When the stored energy is fixed for both cases, the required power differs roughly a factor of $$sim1.7$$ and the identical spatial profiles of electron density $$n_mathrm{e}$$, electron temperature $$T_mathrm{e}$$ and ion temperature $$T_mathrm{i}$$ are obtained. Despite almost the same power crossing the separatrix, type-I ELM frequency for hydrogen becomes approximately in double from that for deuterium. The pedestal pressure differs approximately by a factor of $$sim2$$ for the cases between hydrogen and deuterium plasmas at a given absorbed power. The relation between $$beta_mathrm{p}^mathrm{TOT}$$ and $$beta_mathrm{p}^mathrm{ped}$$ is almost identical regardless of the difference of the isotropic composition.

Journal Articles

The Unified effect of counter-toroidal rotation and power across separatrix on type-I ELMs in JT-60U

Urano, Hajime; Oyama, Naoyuki; Kamiya, Kensaku; Aiba, Nobuyuki; Kamada, Yutaka; Fujita, Takaaki; JT-60 Team

Nuclear Fusion, 52(10), p.103012_1 - 103012_7, 2012/10

 Times Cited Count:2 Percentile:9.2(Physics, Fluids & Plasmas)

The unified effect of counter toroidal rotation and heating power on type-I ELMs was investigated in JT-60U tokamak. ELM frequency $$f_mathrm{ELM}$$ increased monotonically together with the power across the sepratrix $$P_mathrm{sep}$$ for all the cases of tangential NBs. However, dependence of $$f_mathrm{ELM}$$ on $$P_mathrm{sep}$$ was explicitly stronger than a proportional relation when the perpendicular NBs were injected. The toroidal rotation velocity at the H-mode pedestal $$V$$$$rm_T^{rm PED}$$ shifted continuously in counter direction when the perpendicular NBs were applied. At fixed values of $$V$$$$rm_T^{rm PED}$$, $$f_mathrm{ELM}$$ increased clearly in proportion to $$P_mathrm{sep}$$.

Journal Articles

Energy confinement characterization of hydrogen and deuterium H-mode plasmas in JT-60U tokamak

Urano, Hajime; Takizuka, Tomonori*; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Hayashi, Nobuhiko; Oyama, Naoyuki; Kamada, Yutaka; JT-60 Team

Europhysics Conference Abstracts (Internet), 36F, p.P1.016_1 - P1.016_4, 2012/00

Energy confinement properties for hydrogen and deuterium H-mode plasmas were examined in JT-60U. The energy confinement time became larger by a factor of $$sim$$1.2-1.3 for deuterium than for hydrogen at a given $$P_mathrm{L}$$. When the plasma energy was fixed, the profiles of density and temperature became identical for both cases while higher heating power was required for hydrogen. The ion conductive heat flux for hydrogen became approximately two times that for deuterium. Hence, the ion heat diffusivity for hydrogen was higher than for deuterium. It was found that the ion-temperature-gradient scale length became smaller by a factor of $$sim$$1.2 for deuterium than for hydrogen.

Journal Articles

Development of function-graded proton exchange membrane for PEFC using heavy ion beam irradiation

Shiraki, Fumiya*; Yoshikawa, Taeko*; Oshima, Akihiro*; Oshima, Yuji*; Takasawa, Yuya*; Fukutake, Naoyuki*; Oyama, Tomoko*; Urakawa, Tatsuya*; Fujita, Hajime*; Takahashi, Tomohiro*; et al.

Nuclear Instruments and Methods in Physics Research B, 269(15), p.1777 - 1781, 2011/08

 Times Cited Count:7 Percentile:50.3(Instruments & Instrumentation)

The graded energy deposition of heavy ion beam irradiation to polymeric materials was utilized to synthesize a novel proton exchange membrane (PEM) with the graded density of sulfonic acid groups toward the thickness direction. Stacked Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films were irradiated by Xe$$^{54+}$$ ion beam with the energy of 6 MeV/u under a vacuum condition. Irradiated films were grafted with styrene monomer and then sulfonated. The membrane electrode assembly (MEA) fabricated by the function graded PEM showed improved fuel cell performance in terms of voltage stability. It was expected that the function-graded PEM could control the graded concentration of sulfonic acid groups in PEM.

Journal Articles

Core transport properties in JT-60U and JET identity plasmas

Litaudon, X.*; Sakamoto, Yoshiteru; de Vries, P. C.*; Salmi, A.*; Tala, T.*; Angioni, C.*; Benkadda, S.*; Beurskens, M. N. A.*; Bourdelle, C.*; Brix, M.*; et al.

Nuclear Fusion, 51(7), p.073020_1 - 073020_13, 2011/07

 Times Cited Count:8 Percentile:35.64(Physics, Fluids & Plasmas)

A variety of triggering mechanisms and structures of internal transport barrier (ITB) has been observed in various devices or depending on operation scenarios. Thus identity experiments on ITB in JT-60U and JET have been performed to shed light on the physics behind ITBs. Because of their similar size, the dimensionless parameters between both devices are the same. These experiments were performed with near identical magnetic configurations, heating waveforms and normalized quantities such as safety factor, magnetic shear, normalized Larmor radius, normalized collision frequency, beta, temperatures ratio. Similarities of the ITB triggering mechanism and the ITB strength have been observed when a proper match is achieved of the most relevant profiles of the normalized quantities. This paper will report on the detail comparison of transport properties of ITBs obtained in these JET/JT-60U identity experiments.

Journal Articles

Measurement of type-I ELM pulse propagation in SOL through BES use of MSE diagnostics in JT-60U and impact of ELM on MSE diagnostics

Suzuki, Takahiro; Oyama, Naoyuki; Asakura, Nobuyuki; Fujita, Takaaki

Proceedings of 37th European Physical Society Conference on Plasma Physics (EPS 2010) (CD-ROM), 4 Pages, 2010/06

Since transient heat and particle loads by the type-I ELMs are significantly high for the plasma facing components of the fusion reactor, understanding propagation of plasma ejected by ELMs (ELM pulse) in SOL is important. Increase in the SOL plasma density due to the ELM pulse has been measured through the increase in beam emission (BE) at various radial locations in SOL near equatorial plane, using MSE diagnostics as beam emission spectroscopy (BES) diagnostics. From the temporal delay of the increase of BE as a function of major radius in the SOL, radial velocity of the ELM pulse propagation has been evaluated as 0.8-1.8 km/s. In accurately evaluating the velocity, elimination of background (BG) light from the BES signal is found essential since the delay of the net BE is veiled by the BG light that increases in synchronous to the ELM pulse. The intermittent increase in the BG light synchronized with ELMs has been observed in MSE channels viewing not only the SOL but also the main plasma. Since this BG light affects the magnetic pitch angle measurement by MSE diagnostics as was reported in JET, the impact of the intermittent BG light by ELMs on MSE diagnostics has been investigated numerically. When intermittent BG light by ELMs mixes with PEM modulation for MSE diagnostics, broadband spectrum of the impulse-like BG light disturbs the spectrum intensities, even if the BG light is not polarized. Numerical simulation shows that error induced by ELMs piles up if ELM frequency is higher than $$1/tau_{LPF}$$, where $$tau_{LPF}$$ is time constant of lock-in amplifier detecting PEM modulation, and then, the error remains even between ELMs.

Journal Articles

Development of a lithium beam probe and measurement of density pedestal in JT-60U

Kojima, Atsushi; Kamiya, Kensaku; Fujita, Takaaki; Kubo, Hirotaka; Iguchi, Harukazu*; Oyama, Naoyuki; Suzuki, Takahiro; Kamada, Yutaka; JT-60 Team

Plasma and Fusion Research (Internet), 5, p.015_1 - 015_7, 2010/04

A lithium beam probe (LiBP) has been developed for the measurement of electron density profiles with high spatial and temporal resolutions in JT-60U. Using an electron beam heating ion source with a capability of 10 mA extraction, a 5.5 mA beam has been injected to the plasmas. Using the LiBP, time evolutions of pedestal density profiles during type I and grassy edge localized modes (ELMs) have been obtained for the first time. After a type I ELM crash, the drop of the line-integrated density measured by an interferometer delays by 2 ms later than that of the pedestal density. Comparing the line-integrated density to the line integration of the edge density profile measured by the LiBP, it is found that the recovery from the type I ELM crash is correlated with the reduction of core plasma density. Compared with the type I ELM, grassy ELMs have smaller density crashes than that of type I ELMs, which is mainly derived from the narrower ELM affected area.

Journal Articles

Fast dynamics of type I and grassy ELMs in JT-60U

Kojima, Atsushi; Oyama, Naoyuki; Sakamoto, Yoshiteru; Kamada, Yutaka; Urano, Hajime; Kamiya, Kensaku; Fujita, Takaaki; Kubo, Hirotaka; Aiba, Nobuyuki; JT-60 Team

Nuclear Fusion, 49(11), p.115008_1 - 115008_8, 2009/11

 Times Cited Count:18 Percentile:57.81(Physics, Fluids & Plasmas)

In order to understand the physics of the ELM trigger and determining the ELM size, the fast ELM dynamics of type I and grassy ELMs have been studied in JT-60U, using new fast diagnostics with high spatial and temporal resolutions. The evolution of the ion pressure profile in the pedestal region is evaluated for the first time by detailed edge profile measurements. Type I ELMs observed in co-rotating plasmas exhibited larger and wider ELM affected area than ctr-rotating plasmas. Just before type I ELM crash, the pedestal ion pressure and its maximum gradient in co-rotating plasmas are 20% and 12% higher than those in ctr-rotating plasmas, respectively. It is found that the radial extent of the ion pressure gradient at the pedestal region in co-rotating plasmas is 14% wider than that in ctr-rotating plasmas. The experimental results suggest that the ELM size is determined by the structure of the plasma pressure in the whole pedestal region.

Journal Articles

Rotational stabilization of resistive wall mode on JT-60U

Matsunaga, Go; Takechi, Manabu; Aiba, Nobuyuki; Kurita, Genichi; Sakamoto, Yoshiteru; Koide, Yoshihiko; Isayama, Akihiko; Suzuki, Takahiro; Fujita, Takaaki; Oyama, Naoyuki; et al.

Plasma and Fusion Research (Internet), 4, p.051_1 - 051_7, 2009/11

no abstracts in English

Journal Articles

The Impact of the current density profile on heat transport and pedestal structure in JT-60U

Urano, Hajime; Sakamoto, Yoshiteru; Suzuki, Takahiro; Fujita, Takaaki; Kamiya, Kensaku; Isayama, Akihiko; Kamada, Yutaka; Takenaga, Hidenobu; Oyama, Naoyuki; Matsunaga, Go; et al.

Nuclear Fusion, 49(9), p.095006_1 - 095006_7, 2009/09

 Times Cited Count:6 Percentile:24.61(Physics, Fluids & Plasmas)

H-modes operated at higher $$l_mathrm{i}$$ with the current ramp down have shown higher energy confinement with higher density in JT-60U. The $$H$$-factor evaluated for the core plasma depends strongly on $$l_mathrm{i}$$ with the relation of $$H_mathrm{89core} propto l_mathrm{i}^{0.8}$$ for the case without sawtooth activities. Center peaked profiles of electron density and electron temperature are obtained in high $$l_mathrm{i}$$ H-modes. The pedestal pressure is not significantly changed. The enhanced energy confinement in high $$l_mathrm{i}$$ H-modes is attributed to the core improvement with the peaked profiles of electron density and temperature. The electron heat diffusivity is reduced at the plasma core in high $$l_mathrm{i}$$ case, resulting in the center peaked $$T_mathrm{e}$$ profile while the $$T_mathrm{i}$$ profiles are approximately unchanged.

Journal Articles

Development of reversed shear plasmas with high bootstrap current fraction towards reactor relevant regime in JT-60U

Sakamoto, Yoshiteru; Matsunaga, Go; Oyama, Naoyuki; Suzuki, Takahiro; Aiba, Nobuyuki; Takenaga, Hidenobu; Isayama, Akihiko; Shinohara, Koji; Yoshida, Maiko; Takechi, Manabu; et al.

Nuclear Fusion, 49(9), p.095017_1 - 095017_8, 2009/09

 Times Cited Count:27 Percentile:71.06(Physics, Fluids & Plasmas)

This paper reports the recent development of reversed shear plasmas with a high bootstrap current fraction towards reactor relevant regime, especially lower $$q$$$$_{95}$$ regime. By utilizing large volume configuration close to the conductive wall for wall stabilization, the beta limit of the reversed shear plasmas is significantly improved. As a result, high confinement reversed shear plasmas with high bootstrap current fraction exceeding no-wall beta limit are obtained in reactor relevant regime, where $$beta$$$$_{rm N}$$ of 2.7, $$beta$$$$_{rm P}$$ of 2.3 is achieved with reversed $$q$$ profile with $$q$$$$_{rm min}$$ of 2.3, and then HH$$_{rm 98y2}$$ of 1.7, $$n$$$$_{rm e}$$/$$n$$$$_{rm GW}$$ of 0.87 and $$f$$$$_{rm BS}$$ of 0.9 are also obtained at $$q$$$$_{95}$$ of 5.3.

Journal Articles

Dynamics of ion internal transport barrier in LHD heliotron and JT-60U tokamak plasmas

Ida, Katsumi*; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Takenaga, Hidenobu; Nagaoka, Kenichi*; Hayashi, Nobuhiko; Oyama, Naoyuki; Osakabe, Masaki*; Yokoyama, Masayuki*; Funaba, Hisamichi*; et al.

Nuclear Fusion, 49(9), p.095024_1 - 095024_9, 2009/09

 Times Cited Count:29 Percentile:73.23(Physics, Fluids & Plasmas)

Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outward during the ITB formation regardless of the sign of magnetic shear in JT-60U and the ITB becomes more localized in the plasma with negative magnetic shear. In LHD, the low Te/Ti ratio ($$<$$ 1) of the target plasma for the high power heating is found to be necessary condition to achieve the ITB plasma and the ITB location tends to expand outward or inward depending on the condition of the target plasmas. Associated with the formation of ITB, the carbon density tends to be peaked due to inward convection in JT-60U, while the carbon density becomes hollow due to outward convection in LHD. The outward convection observed in LHD contradicts the prediction by neoclassical theory.

Journal Articles

Development of advanced operation scenarios in weak magnetic-shear regime on JT-60U

Suzuki, Takahiro; Oyama, Naoyuki; Isayama, Akihiko; Sakamoto, Yoshiteru; Fujita, Takaaki; Ide, Shunsuke; Kamada, Yutaka; Naito, Osamu; Sueoka, Michiharu; Moriyama, Shinichi; et al.

Nuclear Fusion, 49(8), p.085003_1 - 085003_8, 2009/08

 Times Cited Count:8 Percentile:31.55(Physics, Fluids & Plasmas)

Fully non-inductive discharge having a relaxed current profile and high bootstrap current fraction f$$_{BS}$$=0.5 has been realized in the high-$$beta$$$$_{p}$$ ELMy H-mode discharge with weak magnetic-shear having q$$_{95}$$=5.8, qmin=2.1, and q(0)=2.4, where qmin and q(0) are the safety factor q at the minimum and the plasma center, respectively. The rest of the plasma current is externally driven by neutral beams (NBs) and lower-hybrid (LH) waves. The safety factor profile evaluated by the motional Stark effect (MSE) diagnostic is kept unchanged during 0.7 s at the end of the full current drive (CD) sustainment for 2 s (1.5 times the current relaxation time $$_{tau R}$$). The loop voltage profile is spatially uniform at 0 V at the end of the sustainment. This demonstration shows, for the first time, that the steady sustainment of ful-CD plasma is possible at high f$$_{BS}$$=0.5 and reasonably low q$$_{95}$$=5.8 regime and is stably controlled by appropriate external current drivers. On the other hand, when the combination of bootstrap current and externally driven current does not match to the steady current profile, slight change in the current profile due to current relaxation resulted in appearance of magnetohydrodynamic (MHD) instability, e.g. neo-classical tearing mode (NTM), in a high beta plasma. This discharge clarifies importance of the demonstration of steady current profile developed here. These discharges contribute to the ITER steady-state operation scenario development.

Journal Articles

Status of JT-60SA tokamak under the EU-JA broader approach agreement

Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.

Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12

 Times Cited Count:17 Percentile:73.86(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Dynamics and stability of resistive wall mode in the JT-60U high-$$beta$$ plasmas

Matsunaga, Go; Sakamoto, Yoshiteru; Aiba, Nobuyuki; Shinohara, Koji; Takechi, Manabu; Suzuki, Takahiro; Fujita, Takaaki; Isayama, Akihiko; Oyama, Naoyuki; Asakura, Nobuyuki; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Journal Articles

Heat transport and pedestal structure of H-mode in the variation of current density profiles in JT-60U

Urano, Hajime; Sakamoto, Yoshiteru; Suzuki, Takahiro; Fujita, Takaaki; Kamiya, Kensaku; Isayama, Akihiko; Kamada, Yutaka; Takenaga, Hidenobu; Oyama, Naoyuki; Matsunaga, Go; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Dependence of the H-mode confinement and pedestal structure on the plasma current is investigated. Higher energy confinement is obtained in higher $$l$$$$_{rm i}$$ H-mode. The profiles of the core $$n$$$$_{rm e}$$ and $$T$$$$_{rm e}$$ are tends to be peaked. The H-factor for the core plasma depends strongly on $$l$$$$_{rm i}$$. Higher energy confinement obtained at higher $$l$$$$_{rm i}$$ is attributed to the core confinement improvement. The edge pedestal pressure is not significantly changed by core current density profile. In both $$I$$$$_{rm p}$$ ramp and $$I$$$$_{rm p}$$ scan experiments, the core energy confinement is improved by the increased core $$B$$$$_{rm p}$$ value. The effect of magnetic shear on the confinement should be investigated in next step study.

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