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Journal Articles

Laser-driven neutron generation realizing single-shot resonance spectroscopy

Yogo, Akifumi*; Lan, Z.*; Arikawa, Yasunobu*; Abe, Yuki*; Mirfayzi, S. R.*; Wei, T.*; Mori, Takato*; Golovin, D.*; Hayakawa, Takehito*; Iwata, Natsumi*; et al.

Physical Review X, 13(1), p.011011_1 - 011011_12, 2023/01

 Times Cited Count:1 Percentile:90.46(Physics, Multidisciplinary)

Journal Articles

Development of evaluation procedure for critical current of periodically bent Nb$$_{3}$$Sn strand

Kajitani, Hideki; Ishiyama, Atsushi*; Agatsuma, Ko*; Murakami, Haruyuki; Hemmi, Tsutomu; Koizumi, Norikiyo

Teion Kogaku, 50(12), p.608 - 615, 2015/12

A cable-in-conduit (CIC) conductor using Nb$$_{3}$$Sn strand is applied to an ITER TF coil. The Nb$$_{3}$$Sn strand in the conductor is periodically bent due to electromagnetic force, which causes degradation of performance. This degradation should be evaluated to predict conductor critical current performance. In a past study, a numerical simulation model was developed to evaluate the superconductivity of a periodically bent single strand. However, this model is not suitable for application to strands in the conductor because of the extensive calculation time. The author thus developed a new analytical model with a much shorter calculation time to evaluate the performance of periodically bent strand. This new model uses the classical model concept of a high transverse resistance model (HTRM). The calculated results show good agreement with the test results of a periodically bent Nb$$_{3}$$Sn strand. This indicates that a more practical solution can be achieved when evaluating the performance of periodically bent strands. Thus, the model developed in this study can be applied to evaluate the performance of conductors incorporating many strands.

Journal Articles

Behavior of Nb$$_{3}$$Sn cable assembled with conduit for ITER central solenoid

Nabara, Yoshihiro; Suwa, Tomone; Takahashi, Yoshikazu; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Sakurai, Takeru; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200305_1 - 4200305_5, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Journal Articles

Optimization of heat treatment of Japanese Nb$$_3$$Sn conductors for toroidal field coils in ITER

Nabara, Yoshihiro; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Suwa, Tomone; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.6000605_1 - 6000605_5, 2014/06

 Times Cited Count:7 Percentile:39.64(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Algorithm-based modeling of fractional ion abundance and rates of ionization and recombination for tungsten plasmas

Sasaki, Akira; Murakami, Izumi*

Journal of Physics B; Atomic, Molecular and Optical Physics, 46(17), p.175701_1 - 175701_11, 2013/09

 Times Cited Count:9 Percentile:45.33(Optics)

The fractional ion abundance and rates of ionization and recombination of multiple charged tungsten ions in magnetic fusion plasmas are investigated using a collisional radiative model. Using a computer algorithm to generate a complete set of atomic states to be included into the collisional radiative model, the level population and ion abundance are calculated taking a sufficient number of dieletronic recombination and excitation autoionization channels into account. The atomic data, such as energy levels and rates of radiative decay as well as autoionization are provided from the ab-initio calculation using the HULLAC. The ion abundance is shown to converge with respect to the size of the model in the temperature range of 100 eV to 5 keV, and the ratio between the abundances of W$$^{44+}$$ and W$$^{45+}$$ ions agrees well with an experimental result obtained without any artificial adjustment of atomic rates.

Journal Articles

Data of heavy elements for light sources in EUV and XUV and for other applications

Koike, Fumihiro*; Funaba, Hisamichi*; Goto, Motoshi*; Kato, Daiji*; Kato, Takako*; Morita, Shigeru*; Murakami, Izumi*; Sakaue, Hiroyuki*; Sudo, Shigeru*; Suzuki, Chihiro*; et al.

AIP Conference Proceedings 1545, p.202 - 211, 2013/07

 Times Cited Count:4 Percentile:83.62

Atomic ionic states and transition properties of elements with atomic numbers Z ranging from 50 to 80 are discussed as these are important to the understanding of plasmas containing such heavy elements. As such, data productions and the current status of theoretical calculations in this field are discussed. Further, recent spectroscopic measurements and respective theoretical analyses for W, Gd, and Nd are provided.

Journal Articles

A Study of tungsten spectra using Large Helical Device and Compact Electron Beam Ion Trap in NIFS

Morita, Shigeru*; Dong, C. F.*; Goto, Motoshi*; Kato, Daiji*; Murakami, Izumi*; Sakaue, Hiroyuki*; Hasuo, Masahiro*; Koike, Fumihiro*; Nakamura, Nobuyuki*; Oishi, Tetsutaro*; et al.

AIP Conference Proceedings 1545, p.143 - 152, 2013/07

 Times Cited Count:28 Percentile:99.16

Tungsten spectra have been observed from Large Helical Device (LHD) and Compact electron Beam Ion Trap (CoBIT) in wavelength ranges of visible to EUV. The tungsten spectra from LHD are well analyzed based on the knowledge from CoBIT tungsten spectra. The C-R model code has been developed to explain the UTA spectra in details. Radial profiles of EUV spectra from highly ionized tungsten ions have been measured and analyzed by impurity transport simulation code with ADPAK atomic database code to examine the ionization balance determined by ionization and recombination rate coefficients. The ablation cloud of the impurity pellet is directly measured with visible spectroscopy.

Journal Articles

Cable twist pitch variation in Nb$$_{3}$$Sn conductors for ITER toroidal field coils in Japan

Takahashi, Yoshikazu; Nabara, Yoshihiro; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Hamada, Kazuya; Matsui, Kunihiro; Kawano, Katsumi; Koizumi, Norikiyo; Oshikiri, Masayuki; et al.

IEEE Transactions on Applied Superconductivity, 23(3), p.4801504_1 - 4801504_4, 2013/06

 Times Cited Count:11 Percentile:50.68(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency (JAEA) is the first to start the mass production of the TF conductors in March 2010 among the 6 parties who are procuring TF conductors in the ITER project. The height and width of the TF coils are 14 m and 9 m, respectively. The conductor is cable-in-conduit conductor (CICC) with a central spiral. A circular multistage superconducting cable is inserted into a circular stainless steel jacket with a thickness of 2 mm. A total of 900 Nb$$_{3}$$Sn strands and 522 copper strands are cabled around the central spiral and the cable is inserted into a round-in-round stainless steel jacket. It was observed that the cabling pitch of the destructive sample is longer than the original pitch at cabling. The JAEA carried out the tensile tests of the cable and the measurement of the cable rotation during the insertion to investigate the cause of the elongation. The cause of elongation was clarified and the results will be described in this paper.

Journal Articles

Analytical study of degradation of CIC conductor performance due to strand bending and buckling

Kajitani, Hideki; Hemmi, Tsutomu; Murakami, Haruyuki; Koizumi, Norikiyo

IEEE Transactions on Applied Superconductivity, 23(3), p.6001505_1 - 6001505_5, 2013/06

 Times Cited Count:6 Percentile:35.14(Engineering, Electrical & Electronic)

Critical current of cable-in-conduit conductors (CICCs) for ITER TF coils was measured. It was found from these test results that the measured critical current was lower than that evaluated from the critical current performance of a single strand. One of the explanations for this phenomenon is a non-uniform current distribution due to (1) unbalanced resistance among strands and between the strand and the upper/bottom joint and (2) local degradation of strand in the conductor. It is reported that the former was improved by using solder-filled joint but the latter issue seems to still remain. Therefore, the author developed a new analysis model for the calculation of strain distribution in the conductor taking account of strand bending and buckling and then, combined this with the electrical circuit model developed by authors before. Simulation results show that when local degradation is significant, the conductor performance can be degraded. In this presentation, these results are reported.

Journal Articles

Validation of collisional radiative model of high-Z multiple charged ions at NLTE code comparison workshops

Sasaki, Akira; Murakami, Izumi*

Plasma and Fusion Research (Internet), 8(Sp.1), p.2401021_1 - 2401021_4, 2013/03

We develop a CR model of W based on the computational atomic data for a variety of basic and application researches. We calculate the mean charge and radiative power loss from the plasma and the results are compared with those from different calculations and experimental data at the non-LTE kinetics workshops. We define the groups of levels, which have a same core configuration and one excited electron, and carry out iterative calculations increasing the number of groups according to the energy of the core state, to include a sufficient dielectronic recombination channels. We show the results agree well with other calculations and experiments

Journal Articles

Modifications to the edge radial electric field by angular momentum injection in JT-60U and their implication for pedestal transport

Kamiya, Kensaku; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Yoshida, Maiko; Sakamoto, Yoshiteru; Matsunaga, Go; Oyama, Naoyuki; Koide, Yoshihiko; Kamada, Yutaka; et al.

Nuclear Fusion, 52(11), p.114010_1 - 114010_12, 2012/10

 Times Cited Count:10 Percentile:40.96(Physics, Fluids & Plasmas)

Depending on the direction of the external tangential momentum input, substantial changes in not only toroidal but also poloidal flows for the carbon impurity ions are observed at around the $$E$$$$_{r}$$-well region. The shear in the edge $$E$$$$_{r}$$ becomes wider in the co-NBI case, while the edge $$E$$$$_{r}$$-well becomes deeper in the counter-NBI case.

Journal Articles

Spectroscopic study of $$^{63}$$Ni via cold neutron capture reaction, 1; Nuclear structure of $$^{63}$$Ni

Oshima, Masumi; Kin, Tadahiro*; Nakamura, Shoji; Homma, Michio*; Minato, Futoshi; Hayakawa, Takehito; Hara, Kaoru; Kimura, Atsushi; Koizumi, Mitsuo; Harada, Hideo; et al.

Journal of the Physical Society of Japan, 81(8), p.084201_1 - 084201_15, 2012/08

 Times Cited Count:2 Percentile:19.32(Physics, Multidisciplinary)

The $$gamma$$-radiation has been investigated produced by cold neutron capture in an enriched $$^{62}$$Ni sample. The 315 $$gamma$$-rays have been placed in the $$^{63}$$Ni level scheme of which 272 placements are new. We have determined excitation energies with 0.2-0.8 keV error and branching ratios of 62 bound levels in $$^{63}$$Ni, including 30 new levels. The Q-value of the $$^{62}$$Ni (n,$$gamma$$) $$^{63}$$Ni reaction amounts to 6837.75 (18) keV. A large-scale shell-model calculation has been performed and the energies of the low-lying $$^{63}$$Ni states are successfully reproduced. A mean-field statistical model calculation has been also made by using a self-consistent interaction between the Hartree-Fock + BCS method and the statistical calculation. The calculation result is consistent with the experimental level density of $$^{63}$$Ni.

Journal Articles

Feasibility study for the quantification of total protein content by multiple prompt $$gamma$$-ray analysis

Toh, Yosuke; Murakami, Yukihiro*; Furutaka, Kazuyoshi; Kimura, Atsushi; Koizumi, Mitsuo; Hara, Kaoru; Kin, Tadahiro; Nakamura, Shoji; Harada, Hideo

Applied Radiation and Isotopes, 70(6), p.984 - 987, 2012/06

 Times Cited Count:3 Percentile:32.06(Chemistry, Inorganic & Nuclear)

By applying the multiple $$gamma$$-ray detection method to prompt $$gamma$$-ray analysis, called MPGA (multiple prompt $$gamma$$-ray analysis), the interference from hydrogen contained in a sample can be reduced. Therefore, this method can improve the signal-to-noise ratio, and provide a rapid screening method of toxic elements. We developed a neutron beam line and a detector system for MPGA, which consists of eight Clover Ge detectors, was constructed at the cold neutron guide C2-3-2 of JRR-3. Protein is an important nutrient in foods. The classical total protein analysis method is the Kjeldahl technique, which is time-consuming and inconvenient. As a convenient method to quantify total protein content in biological samples, the feasibility of application of MPGA to the quantification was studied. The results obtained with reference materials are in good agreement with the certified value. MPGA provides a tool for the rapid and non-destructive quantification of total protein content.

Journal Articles

Mass production of Nb$$_{3}$$Sn conductors for ITER toroidal field coils in Japan

Takahashi, Yoshikazu; Isono, Takaaki; Hamada, Kazuya; Nunoya, Yoshihiko; Nabara, Yoshihiro; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Oshikiri, Masayuki; et al.

IEEE Transactions on Applied Superconductivity, 22(3), p.4801904_1 - 4801904_4, 2012/06

 Times Cited Count:7 Percentile:41.46(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency is the first to start the mass production of the TF conductors in Phase IV in March 2010 among the 6 parties who are procuring TF conductors in the ITER project. The conductor is cable-in-conduit conductor with a central spiral. A total of 900 Nb$$_{3}$$Sn strands and 522 copper strands are cabled around the central spiral and then wrapped with stainless steel tape whose thickness is 0.1 mm. Approximately 60 tons of Nb$$_{3}$$Sn strands were manufactured by the two suppliers in December 2010. This amount corresponds to approximately 55% of the total contribution from Japan. Approximately 30% of the total contribution from Japan was completed as of February 2011. JAEA is manufacturing one conductor per month under a contract with two Japanese companies for strands, one company for cabling and one company for jacketing. This paper summarizes the technical developments including a high-level quality assurance. This progress is a significant step in the construction of the ITER machine.

Journal Articles

Chemical composition of sediments from marine shallow-water hydrothermal mounds in Wakamiko submarine crater revealed by multiple prompt $$gamma$$-ray analysis

Shozugawa, Katsumi*; Matsuo, Motoyuki*; Sano, Yuji*; Toh, Yosuke; Murakami, Yukihiro*; Furutaka, Kazuyoshi; Koizumi, Mitsuo; Kimura, Atsushi; Hara, Kaoru; Kin, Tadahiro; et al.

Journal of Radioanalytical and Nuclear Chemistry, 291(2), p.341 - 346, 2012/02

 Times Cited Count:3 Percentile:25.07(Chemistry, Analytical)

Multiple prompt $$gamma$$-ray analysis (MPGA), a new quantification method with high energy resolution, was applied to sediments from a marine shallow-water hydrothermal mound. Surface sediments around mounds were collected from the Wakamiko submarine crater located in Kagoshima Bay, southwest Japan, where the hydrothermal system was different from those at other marine shallow-water hydrothermal mounds. All samples were desalted and MPGA measurements were performed for 4,500 s (real time). Event data were obtained using eight CLOVER Ge detectors. We could obtain concentrations of $$^{32}$$S, $$^{55}$$Mn, $$^{75}$$As, $$^{157}$$Gd, $$^{39}$$K, $$^{149}$$Sm, $$^{56}$$Fe, and $$^{85}$$Rb with high sensitivity by MPGA. Furthermore, $$^{32}$$S, $$^{85}$$Rb, and $$^{55}$$Mn have characteristic concentrations only at a mound, suggesting that sediments were sulfated by magmatic fluids at this mound.

Journal Articles

Application of multiple prompt $$gamma$$-ray analysis (MPGA) to geochemical and cosmochemical samples

Oura, Yasuji*; Watanabe, Ryo*; Ebihara, Mitsuru*; Murakami, Yukihiro*; Toh, Yosuke; Kimura, Atsushi; Koizumi, Mitsuo; Furutaka, Kazuyoshi; Oshima, Masumi; Hara, Kaoru; et al.

Journal of Radioanalytical and Nuclear Chemistry, 291(2), p.335 - 339, 2012/02

 Times Cited Count:4 Percentile:32.06(Chemistry, Analytical)

We applied multiple prompt $$gamma$$-ray analysis (MPGA) method to geochemical and cosmochemical samples to evaluate its analytical performance on signal to noise (S/N) ratio, sensitivity, and detection limit. The S/N ratio measured by MPGA system was larger than that by normal prompt $$gamma$$ ray activation analysis (PGAA) at JRR3. For some elements, the S/N ratio was improved more than ten times. Several elements that are not detected by PGAA were detected by MPGA. In the present experiment, concentrations of major elements and trace elements with high neutron capture cross section in geochemical and cosmochemical samples were determined accurately by the MPGA system. It is expected that it will determine a lot of trace elements after appropriate adjustments and modifications.

Journal Articles

Numerical simulation of current distribution in cable-in-conduit conductor for ITER TF coil

Kajitani, Hideki*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Murakami, Haruyuki; Nakajima, Hideo

IEEE Transactions on Applied Superconductivity, 21(3), p.1964 - 1968, 2011/06

 Times Cited Count:3 Percentile:29.22(Engineering, Electrical & Electronic)

The critical current of cable-in-conduit conductor (CICC) for ITER TF coil was measured using SULTAN test facility. However, it was found that a non-uniform current distribution was established due to a non-uniform joint resistance. To more precisely evaluate critical current performance, solder filling joint was applied. To study the effect of solder filled joint on the current distribution, the authors developed a new analysis model. The lumped circuit model and distributed circuit model were used for the conductor and joint, respectively, and they are combined. This allow us to avoid iteration to solve distributed circuit equation, resulting in much reduction of calculation time. The simulation results show that although non-uniform current distribution can be established by ramping current, it is improved at current sharing temperature. Thus, the efficiency of solder filling joint is indicated.

Journal Articles

Analytical model of the critical current of a bent Nb$$_{3}$$Sn strand

Koizumi, Norikiyo; Murakami, Haruyuki; Hemmi, Tsutomu; Nakajima, Hideo

Superconductor Science and Technology, 24(5), p.055009_1 - 055009_12, 2011/05

 Times Cited Count:18 Percentile:59.63(Physics, Applied)

Critical current performance of a large Nb$$_{3}$$Sn cable-in-conduit conductor (CICC) was degraded by periodic bending of strands due to a large transverse electromagnetic force. The degradation of each strand due to this bending should be evaluated in calculations of the critical current of a CICC, but a suitable model has not been developed yet. Therefore, the authors have developed a new analytical model which takes into account plastic deformation of copper and bronze and filament breakage. Calculated results were compared with test results for uniformly bent Nb$$_{3}$$Sn bronze-route strands. Calculated results assuming a high-transverse resistance model (HTRM) show good agreement with the test results, a finding which confirms the validity of the model. Because of a much shorter calculation time than for numerical simulation, the developed model seems much more practical for use in calculating the critical current performance of a Nb$$_{3}$$Sn CICC. In addition, simulation results show that since the neutral axis of a bent strand shifts to the compressive side due to plastic deformation of the copper and bronze, and/or filament breakage, the strand is elongated by bending. This elongation may enhance the strand's critical current performance. Moreover, calculated results indicate that dependence of the critical current on the bending strain is affected by the bending history if the strand is excessively bent, especially when filaments are broken. In a real magnet, since a strand in a CICC is normally subject to the maximum electromagnetic force prior to an evaluation of its performance at a lower electromagnetic force, the effect of over-bending should be taken into account in calculations of its critical current performance, especially when filament breakage occurs.

Journal Articles

An Automatic liquid-nitrogen filling system for multiple Ge detectors

Koizumi, Mitsuo; Oshima, Masumi; Toh, Yosuke; Kimura, Atsushi; Kin, Tadahiro; Furutaka, Kazuyoshi; Murakami, Yukihiro*; Osa, Akihiko; Ando, Shingo*

Review of Scientific Instruments, 80(1), p.016102_1 - 016102_3, 2009/01

 Times Cited Count:2 Percentile:12.56(Instruments & Instrumentation)

In order to reduce time and effort of the daily task of refilling Dewar vessels of Ge detectors with LN$$_2$$, we have developed an automatic LN$$_2$$ filling system equipped with an LN$$_2$$ plant. With the system, our multiple Ge detector system became almost maintenance free. Such an LN$$_2$$ filling system is useful for moderate-scale Ge detector arrays consisting of less than 20 Ge detectors.

Journal Articles

Numerical simulation of critical current performance in Nb$$_{3}$$Sn strand subjected to periodic bending deformation

Murakami, Haruyuki*; Ueda, Hiroshi*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Okuno, Kiyoshi

Denki Gakkai Rombunshi, B, 128(6), p.853 - 859, 2008/06

In the ITER Engineering Design Activity (EDA), it was revealed the critical current of the Nb$$_{3}$$Sn model coil conductor degraded by periodic strand bending caused by enormous electromagnetic force. We developed a simulation code based on the distributed circuit to investigate dependency of the critical current performance on bending strain. The results of the numerical simulations were in good agreement with the experiments. The dependence of the critical current on periodic transverse load, temperature, pitch of periodic load, thickness of Ta barrier which prevents Cu stabilizer to be contaminated by Sn, twist pitch of the strand and RRR of the bronze matrix is investigated using developed code. The results show the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that shorter twist pitch of the cable and larger bending stiffness prevent the critical current degradation.

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