Oba, Yojiro; Sasaki, Hirokazu*; Yamazaki, Satoshi*; Nakasaki, Ryusuke*; Onuma, Masato*
Superconductor Science and Technology, 32(5), p.055011_1 - 055011_5, 2019/05
Sueyoshi, Tetsuro*; Nishimura, Takahiro*; Fujiyoshi, Takanori*; Mitsugi, Fumiaki*; Ikegami, Tomoaki*; Ishikawa, Norito
Superconductor Science and Technology, 29(10), p.105006_1 - 105006_7, 2016/10
A systematic investigation of flux pinning by widely direction-dispersed columnar defects (CDs) in YBaCuOy thin films was carried out by using heavy-ion irradiation: a parallel configuration of CDs aligned along the -axis, and two trimodal splay configurations composed of crossing CDs; relative to the -axis, where the splay plane defined by the three irradiation angles is perpendicular (trimodal-A) or parallel (trimodal-B) to the transport current direction. The trimodal configurations show high pinning efficiency over a wide range of magnetic field orientations compared to the parallel one at low magnetic field. In particular, trimodal-B shows the higher critical current density of the two trimodal configurations.
Osamura, Kozo*; Machiya, Shutaro*; Hampshire, D. P.*; Tsuchiya, Yoshinori*; Shobu, Takahisa; Kajiwara, Kentaro*; Osabe, Goro*; Yamazaki, Kohei*; Yamada, Yuichi*; Fujikami, Jun*
Superconductor Science and Technology, 27(8), p.085005_1 - 085005_11, 2014/08
Hemmi, Tsutomu; Harjo, S.; Nunoya, Yoshihiko; Kajitani, Hideki; Koizumi, Norikiyo; Aizawa, Kazuya; Machiya, Shutaro*; Osamura, Kozo*
Superconductor Science and Technology, 26(8), p.084002_1 - 084002_6, 2013/08
JAEA has responsibly to procure all ITER CS conductors. Several conductor samples was fabricated and tested. From the result of the cyclic testing in first conductor sample named JACS01 and second conductor sample named JACS02, the continuous linear degradation of the current sharing temperature () was observed. To investigate the degradation, the visual inspection of JACS01 right leg was performed. As a result, the large deflection at the lower loading side (LLS) in the high field zone (HFZ) was observed. The bending strain of the strands cannot be evaluated from the only deflection obtained by a visual inspection. To evaluate the strain of strands in the conductor sample quantitatively, the neutron diffraction measurement of JACS01 left leg was performed using the engineering materials diffractometer in J-PARC. From the result, the large bending strain at the LLS in the HFZ was observed. Therefore, the degraded position in the conductor sample can be determined.
Tamegai, Tsuyoshi*; Taen, Toshihiro*; Yagyuda, Hidenori*; Tsuchiya, Yuji*; Mohan, S.*; Taniguchi, Tomotaka*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; et al.
Superconductor Science and Technology, 25(8), p.084008_1 - 084008_14, 2012/08
Various kinds of energetic particles are irradiated into iron-based superconductors, and their effects on the critical current density and vortex dynamics have been systematically studied. It is found that is enhanced and vortex dynamics is strongly suppressed by energetic particles having a sufficient energy deposition rate, similar to the case of high temperature cuprate superconductors. The enhancement of , in general, persists up to much higher irradiation doses than in cuprates. However, details of the effect of irradiation depend on the kind of ion species and their energies. Even with the same ions and energies, the effect is not universal for different kinds of iron-based superconductors. The correlated nature of defects created by heavy-ion irradiation is confirmed by the angular dependence of irreversible magnetization.
Osamura, Kozo*; Machiya, Shutaro*; Tsuchiya, Yoshinori*; Suzuki, Hiroshi; Shobu, Takahisa; Sato, Masugu*; Hemmi, Tsutomu; Nunoya, Yoshihiko; Ochiai, Shojiro*
Superconductor Science and Technology, 25(5), p.054010_1 - 054010_9, 2012/05
Koizumi, Norikiyo; Murakami, Haruyuki; Hemmi, Tsutomu; Nakajima, Hideo
Superconductor Science and Technology, 24(5), p.055009_1 - 055009_12, 2011/05
Critical current performance of a large NbSn 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 NbSn 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 NbSn 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.
Hikino, Shinichi*; Mori, Michiyasu; Takahashi, Saburo*; Maekawa, Sadamichi
Superconductor Science and Technology, 24(2), p.024008_1 - 024008_5, 2011/02
Barnes, S. E.*; Aprili, M.*; Petkovi, I.*; Maekawa, Sadamichi
Superconductor Science and Technology, 24(2), p.024020_1 - 024020_6, 2011/02
Osamura, Kozo*; Machiya, Shutaro*; Tsuchiya, Yoshinori*; Suzuki, Hiroshi
Superconductor Science and Technology, 23(4), p.045020_1 - 045020_7, 2010/04
The stress/strain behavior of the surround Cu stabilized YBCO coated conductors and its influence on critical current were precisely investigated. The internal strain exerted on the superconducting YBCO layer was determined at 77 K by using a neutron diffraction technique at JAEA. The initial compressive strain decreased during tensile loading and changed to a tensile component at the force free strain (A), where the internal uniaxial stress becomes zero in the YBCO layer. The A was evaluated to be 0.19-0.21% at 77 K. The critical current measurements were carried out under a uniaxial tensile load at 77 K. The strain dependence revealed a characteristic behavior, where a maximum was observed at 0.035%. Thus it was made clear that the strain at the critical current maximum does not correlate with A for YBCO coated conductors.
Machida, Masahiko; Koyama, Tomio*
Superconductor Science and Technology, 20(2), p.S23 - S27, 2007/02
no abstracts in English
Koizumi, Norikiyo; Nunoya, Yoshihiko; Matsui, Kunihiro; Nakajima, Hideo; Ando, Toshinari*; Okuno, Kiyoshi
Superconductor Science and Technology, 16(9), p.1092 - 1096, 2003/09
A 13T-46kA NbAl insert (ALI) has been developed in the ITER-EDA to demonstrate the applicability of react-and-wind technique to TF coil fabrication. Since it is estimated that a conductor is subjected to 0.4% bending strain after heat treatment when the react-and-wind method is applied, 0.4% bending strain was artificially applied to the ALI conductor. Thus, the conductor is subjected to the thermal and bending strains. The strains due to thermal stress and conductor bending are estimated from the critical current test results of the ALI to be 0.4% and 0%, respectively. The thermal strain showed good agreement with the prediction but the axial strain was not applied to the strand by the 0.4% bending. In addition, the evaluated strain of the NbAl conductor is compared with those of NbSn conductors. There was an unexpected strain in the NbSn conductors but the one was not observed in the NbAl conductor. One of the explanations is higher rigidity of the NbAl strand. This shows that an NbAl conductor is suitable to the application to large magnets.
Yoshii, Kenji; Abe, Hideki*
Superconductor Science and Technology, 15(10), p.L25 - L27, 2002/10
no abstracts in English
Keys, S.*; Koizumi, Norikiyo; Hampshire, D.*
Superconductor Science and Technology, 15(7), p.991 - 1010, 2002/07
The critical current density of a jelly-roll NbAl strand was measured at first as a function of magntic field, temperature and strain. The equation to estimate its critical current density has been derived from these test results. The magenti fields, temperatures and strains were less than 15 T, less than 14 K and -1.8 - 0.7% in the experiment.