Evaluation of thermal strain induced in components of NbSn strand during cooling

Suwa, Tomone*; Hemmi, Tsutomu*; Saito, Toru*; Takahashi, Yoshikazu*; Koizumi, Norikiyo*; Luzin, V.*; Suzuki, Hiroshi; Harjo, S.

IEEE Transactions on Applied Superconductivity, 28(3), p.6001104_1 - 6001104_4, 2018/04

https://doi.org/10.1109/TASC.2018.2793190

Overview of national centralized tokamak program; Mission, design and strategy to contribute ITER and DEMO

Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.

Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12

To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.

Doping Momentum dependence of charge dynamics in NdCeCuO (x=0, 0.075, and 0.15) studied by Resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Inami, Toshiya; Tsubota, Masami; Yamada, Kazuyoshi*; et al.

AIP Conference Proceedings 850, p.403 - 404, 2006/09

https://doi.org/10.1063/1.2354756

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high- superconductor NdCeCuO. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with -dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Intelligible seminar on fusion reactors, 9; Superconducting coil to generate magnetic field for plasma confinement

Koizumi, Norikiyo; Nishimura, Arata*

Nihon Genshiryoku Gakkai-Shi, 47(10), p.703 - 708, 2005/10

http://ci.nii.ac.jp/naid/10016378887

no abstracts in English

Rapid normal zone propagation observed in a 13 T-46 kA NbAl cable-in-conduit conductor

Koizumi, Norikiyo; Matsui, Kunihiro; Kume, Etsuo; Okuno, Kiyoshi

IEEE Transactions on Applied Superconductivity, 15(2), p.1363 - 1366, 2005/06

https://doi.org/10.1109/TASC.2005.849089

The NbAl Insert was developed by JAERI aiming at the demonstration of a NbAl conductor to fusion reactor magnets. A quench test was performed on the NbAl Insert at 13 T with various temperature margins, which are defined as a difference between current sharing temperature and operating temperature. The initial normalcy was initiated by using an inductive heater and a coil current was kept for several seconds. The normal zone propagation velocity was accelerated after 3 s from the onset of heating in case that the temperature margin was set at 0.5 K. A simulation using one-dimensional stability and quench simulation code was performed. The calculation results indicate that such rapid propagation occurred due to a temperature rise beyond a current sharing temperature because of a large pressure increase even at the location where the normal front did not reach yet. This large pressure rise was caused since the coolant was contained in the closed circulation circuit of the cooling system, which is usually applied to a large magnet cooling system.

Momentum dependence of charge excitations in the electron-doped superconductor NdCeCuO; A Resonant inelastic X-ray scattering study

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Tsubota, Masami; Inami, Toshiya; Mizuki, Junichiro; et al.

Physical Review Letters, 94(20), p.207003_1 - 207003_4, 2005/05

https://doi.org/10.1103/PhysRevLett.94.207003

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high- superconductor NdCeCuO. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with -dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Phonon anomaly on NaHfNCl superconductors with =22 K

Shamoto, Shinichi; Hirai, Atsuo*; Yamanaka, Shoji*; Aso, Naofumi*; Kajitani, Tsuyoshi*

Journal of Neutron Research, 12(4), p.295 - 300, 2004/12

https://doi.org/10.1080/10238160412331299474

Inelastic neutron scattering measurements have been performed on superconducting NaHfNCl powder samples with x=0.27 and 0.38 (T =22 K). We have observed several temperature dependent phonon anomalies, e.g., at E=15, 29, 76, and 81 meV for the former sample. A phonon peak with E=14.5 meV at Q=6 increases for both samples with decreasing temperature below T=40 K, which is much higher than T. The phonon peak is assigned to an ab-plane vibrational mode, E, of chlorine and hafnium atoms, which strongly modifies the electronic band structure. The phonon anomaly is discussed in terms of carrier inhomogeneity.

Penetration of vortices into micro-superconductors observed with a scanning SQUID microscope

Nishio, Taichiro; Okayasu, Satoru; Suzuki, Junichi; Kadowaki, Kazuo

Physica C, 412-414(Part1), p.379 - 384, 2004/10

We have studied the vortex states in a meoscopic superconductor with geometrical constraints such as disks, triangles, squares, etc. with dimensions between 30-50m using a scanning SQUID microscope (SQM2000,Seiko Instruments Inc.). The sample was fabricated by electron lithography and Focused Ion Beam (FIB) techniques. Quantized vortices enter into a mesoscopic superconductor discretely as a function of magnetic field accompanied by the sequential step-wise jump of magnetization of the superconductor. Quantitative as well as qualitative analyses of spatial vortex arrangement as a function of the number of vortices will be shown in comparison with the recent theoretical predictions.

Superconducting magnet system in a fusion reactor

Okuno, Kiyoshi; Shikov, A.*; Koizumi, Norikiyo

Journal of Nuclear Materials, 329-333(Part1), p.141 - 147, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.151

A tokamak fusion reactor requires a superconducting magnet system for plasma confinement and control. Higher magnetic field of the toroidal field (TF) coil can offer better performance of the reactor. Therefore, fusion magnet development always drives a new superconductor to be used in a large magnet on an industrial basis. Magnets for the International Thermonuclear Experimental Reactor (ITER) use NbSn in order to generate a peak magnetic field of 13 T. Technologies for NbSn superconductor has made a significant progress through the extensive development in ITER including the manufacture of the full-scale model coils. A next generation superconductor, NbAl, has outstanding features of large critical current density at the high field. High Tc (Critical Temperature) superconductor (HTS) is another candidate, and if it becomes available, a magnetic filed above 20 T can be realized in fusion reactor. However, technical issues have to be solved for the application of these innovate superconducting materials in Fusion Reactor.

Development and test results of a 60kA HTS current lead for fusion application

Isono, Takaaki; Hamada, Kazuya; Kawano, Katsumi; Abe, Kanako*; Nunoya, Yoshihiko; Sugimoto, Makoto; Ando, Toshinari*; Okuno, Kiyoshi; Bono, Takaaki*; Tomioka, Akira*; et al.

Teion Kogaku, 39(3), p.122 - 129, 2004/03

https://doi.org/10.2221/jcsj.39.122

JAERI has been developing a large-capacity high-temperature superconductor (HTS) current lead for fusion application, and succeeded in fabricating and testing a 60kA HTS current lead satisfying ITER requirements. Targets of performance are 1/10 heat leak and 1/3 electric power consumption of cryogenic system compared with a conventional lead. To achieve the target, selection of sheath material of HTS, optimizing the Cu part, reduction of joule heat at joint between HTS and Cu parts, improve of heat transfer between HTS and stainless steel tube. Developed 60kA HTS current lead satisfied the design condition and almost achieved the targets. Adoption of the HTS current lead can reduce 13% electric power consumption of cryogenic system for ITER.