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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:40.75(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Examination of Nb$$_{3}$$Sn conductors for ITER central solenoids

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

IEEE Transactions on Applied Superconductivity, 23(3), p.4801604_1 - 4801604_4, 2013/06

 Times Cited Count:10 Percentile:49.06(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Test results of ITER conductors in the SULTAN facility

Bruzzone, P.*; Stepanov, B.*; Wesche, R.*; Mitchell, N.*; Devred, A.*; Nunoya, Yoshihiko; Tronza, V.*; Kim, K.*; Boutboul, T.*; Martovetsky, N.*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Starting March 2007, over 60 ITER cable-in-conduit conductors (CICC) have been tested in the SULTAN test facility, Switzerland. For the NbTi CICC, the results confirm the prediction from the strand data, which are made taking the peak field over the conductor cross section as operating field. All the NbTi samples passed the supplier qualification phase. For the Nb$$_{3}$$Sn CICC, the performance prediction is not straightforward because of the irreversible degradation caused by filament damage occurring during cyclic loading. At the first run of the test campaign, the performance of all the Nb$$_{3}$$Sn samples largely meets the target for all the tested samples. Contrary to the NbTi CICC case, the n-index of the transition is substantially lower than in the strands, providing evidence of irreversible degradation. The performance loss upon load cycles and thermal cycles has a broad range among the various conductor samples.

Journal Articles

Test results and investigation of Tcs degradation in Japanese ITER CS conductor samples

Hemmi, Tsutomu; Nunoya, Yoshihiko; Nabara, Yoshihiro; Yoshikawa, Masatoshi*; Matsui, Kunihiro; Kajitani, Hideki; Hamada, Kazuya; Isono, Takaaki; Takahashi, Yoshikazu; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 22(3), p.4803305_1 - 4803305_5, 2012/06

 Times Cited Count:44 Percentile:86.19(Engineering, Electrical & Electronic)

To characterize the performance of the CS conductor, a CS conductor sample was tested in the SULTAN facility at CRPP. As a result of the cyclic test up to 1000 cycles, measured Tcs was in good agreement with the expected Tcs, which is calculated by the characteristics of the Nb$$_{3}$$Sn strands and the designed strain. However, continuous degradation of Tcs was observed after 1000 cycles. The degradation of Tcs was around 0.6 K from 1000 cycles to 6000 cycles. On the other hand, the degradation of Tcs by cyclic operation is nearly 0.1 K from 1000 cycles to 10,000 cycles in the CS Insert test at JAEA in 2000. To investigate the causes for the degradation of Tcs, the following items are performed; (1) strain measurement by neutron diffraction, (2) strain measurement by sample cuttings, (3) strand position observation, (4) visual inspection on strands, (5) filament breakage observation, (6) modeling and calculation of the degradation. Detailed results will be presented and discussed.

Journal Articles

Examination of Japanese mass-produced Nb$$_3$$Sn conductors for ITER toroidal field coils

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

IEEE Transactions on Applied Superconductivity, 22(3), p.4804804_1 - 4804804_4, 2012/06

 Times Cited Count:17 Percentile:64.95(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Test result of a full-size Nb$$_{3}$$Sn conductor developed for the ITER TF coils

Nunoya, Yoshihiko; Nabara, Yoshihiro; Yoshikawa, Masatoshi*; Matsui, Kunihiro; Hemmi, Tsutomu; Takahashi, Yoshikazu; Isono, Takaaki; Koizumi, Norikiyo; Nakajima, Hideo; Stephanov, B.*; et al.

IEEE Transactions on Applied Superconductivity, 21(3), p.1982 - 1986, 2011/06

 Times Cited Count:21 Percentile:69.88(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency (JAEA) has developed ITER TF Nb$$_{3}$$Sn conductors that fulfill ITER requirements and then commenced fabricating conductors to be used for ITER TF coils. As a qualification of conductor fabrication, two full-size conductor samples named as JATF4 were prepared and tested by the SULTAN facility at CRPP in Switzerland. The length of the samples was about 3 m, and temperature sensors and voltage taps were attached on conductors to measure the current sharing temperature (Tcs). The measurement was performed at the beginning of the test campaign, during cyclic test, and at the end of the campaign that corresponded to after once warm up and cool down. The Tcs values electrically assessed by the agreed procedure at outer magnetic fields of 10.78 T were 6.5 K and 6.2 K at the beginning and 6.1 K and 6.0 K at the end of the campaign for each conductor, respectively. These values concluded that the conductors have enough Tcs margin to satisfy the criterion of 5.7 K as ITER TF conductor, and conductor fabrication is qualified. Detail of the test results will be presented and discussed.

Journal Articles

Test results of the third Japanese SULTAN sample

Matsui, Kunihiro; Isono, Takaaki; Nunoya, Yoshihiko; Hemmi, Tsutomu; Okui, Yoshio*; Oshikiri, Masayuki; Koizumi, Norikiyo; Takahashi, Yoshikazu; Okuno, Kiyoshi; Stepanov, B.*; et al.

IEEE Transactions on Applied Superconductivity, 19(3), p.1470 - 1473, 2009/06

 Times Cited Count:20 Percentile:68.35(Engineering, Electrical & Electronic)

Conductor procurement for ITER Toroidal Field (TF) coils in Japan has just stated in the spring of 2008 under agreement with ITER organization. Before the activity, each Nb$$_{3}$$Sn conductor must be tested at SULTAN facility in Switzerland for qualification of the conductor. The TF conductor is cable-in-conduit type with about 40 mm outer diameter and is composed of 900 Nb$$_{3}$$Sn strands, 522 Cu strands, a central spiral and a 316LN tube. Required performance of the conductor is Tcs of 5.7 K at 68 kA and 11.3 T, which is operating condition of TF coils. Japan has four Nb$$_{3}$$Sn strand suppliers for ITER and two of them were already tested as Japanese 1st and 2nd SULTAN samples. This paper shows test results of 3rd Japanese SULTAN sample using Nb$$_{3}$$Sn strands fabricated by resting two suppliers.

Journal Articles

Performance of Japanese Nb$$_{3}$$Sn conductors for ITER toroidal field coils

Takahashi, Yoshikazu; Isono, Takaaki; Koizumi, Norikiyo; Nunoya, Yoshihiko; Matsui, Kunihiro; Nabara, Yoshihiro; Hemmi, Tsutomu; Oshikiri, Masayuki; Uno, Yasuhiro*; Okuno, Kiyoshi; et al.

IEEE Transactions on Applied Superconductivity, 18(2), p.471 - 474, 2008/06

 Times Cited Count:16 Percentile:63.4(Engineering, Electrical & Electronic)

The ITER TF coil system consists of 18 D-shape coils. The operating current and the maximum field are 68 kA and 11.8 T, respectively. A Nb$$_{3}$$Sn cable-in-conduit conductor with a central channel is used, with a unit length of about 380 m. A cable consists of 900 Nb$$_{3}$$Sn strands and 522 Cu strands with a diameter of 0.82 mm. Superconducting performance of full-size conductors manufactured was measured at the operating condition of the TF coils with the maximum field. The strands made by bronze and internal-Sn methods were used for the sample conductors with a void fraction of 29% and 33%, respectively. The measured current sharing temperatures Tcs are 6.5-6.7K for the bronze route method and 5.7-5.9K for the internal-Sn method. The Tcs of the conductor with small void fraction is relatively higher with 0.1-0.2K than that with large void fraction. It is confirmed that Tcs of both strands is higher than the design value (5.7K). It is shown from the results that the strain on the conductor, estimated by the strand data, is about -0.7%. This value seems to be reasonable.

Journal Articles

Implications of NbTi short-sample test results and analysis for the ITER Poloidal Field Conductor Insert (PFCI)

Zanino, R.*; Bagnasco, M.*; Baker, W.*; Bellina, F.*; Bruzzone, P.*; della Corte, A.*; Ilyin, Y.*; Martovetsky, N.*; Mitchell, N.*; Muzzi, L.*; et al.

IEEE Transactions on Applied Superconductivity, 16(2), p.886 - 889, 2006/06

 Times Cited Count:7 Percentile:41.11(Engineering, Electrical & Electronic)

As the test of the PFCI is foreseen at JAERI Naka, Japan, it is essential to consider in detail the lessons learned from the short NbTi sample tests, as well as the issues left open after them, in order to develop a suitable test program of the PFCI aimed at bridging the extrapolation gap between measured strand and future PF coil performance. Here we consider in particular the following issues: (1) the actual possibility to quench the PFCI conductor in the TCS tests before quenching the intermediate joint, (2) the question of the so-called sudden or premature quench, based on SULTAN sample results, applying a recently developed multi-solid and multi-channel extension of the Mithrandir code to a short sample analysis; (3) the feasibility of the AC losses calorimetry in the PFCI. These results show that Tcs measurement and the calorimetric measurement of AC losses will be carried out successfully. However, we need further analytic works for the problem of the sudden quench.

Journal Articles

Critical current test results of 13T-46kA Nb$$_{3}$$Al cable-in-conduit conductor

Koizumi, Norikiyo; Takahashi, Yoshikazu; Nunoya, Yoshihiko; Matsui, Kunihiro; Ando, Toshinari; Tsuji, Hiroshi; Okuno, Kiyoshi; Azuma, Katsunori*; Fuchs, A.*; Bruzzone, P.*; et al.

Cryogenics, 42(11), p.675 - 690, 2002/11

 Times Cited Count:23 Percentile:65.13(Thermodynamics)

In the framework of ITER-EDA, a 13T-46kA Nb$$_{3}$$Al conductor with stainless steel jacket has been developed to demonstrate applicability of an Nb$$_{3}$$Al conductor with react-and-wind technique to ITER-TF coils. The critical current performances of the Nb$$_{3}$$Al conductors were studied to verify that the conductor achieves the expected performance and 0.4% bending strain does not originate degradation. The critical currents were measured at the background magnetic fields of 7, 9, 10 and 11 T at the temperatures from 6 to 9 K. The expected critical currents is calculated using the developed model and the calculation results indicate that the experimental results showed good agreement with the expected critical currents. Accordingly, we can conclude that the fabrication process of this conductor was appropriate and the applicability of the react-and-wind technique was demonstrated.

Journal Articles

Evaluation of critial current performance of 13 T-46 kA steel-jacketed Nb$$_{3}$$Al conductor

Koizumi, Norikiyo; Azuma, Katsunori*; Tsuchiya, Yoshinori; Matsui, Kunihiro; Takahashi, Yoshikazu; Nakajima, Hideo; Nishijima, Gen; Nunoya, Yoshihiko; Ando, Toshinari; Isono, Takaaki; et al.

Fusion Engineering and Design, 58-59, p.1 - 5, 2001/11

 Times Cited Count:2 Percentile:19.89(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Evaluation of critical current performance of a Nb$$_{3}$$Al conductor with stainless steel conduit

Koizumi, Norikiyo; Takahashi, Yoshikazu; Nakajima, Hideo; Tsuchiya, Yoshinori; Matsui, Kunihiro; Nunoya, Yoshihiko; Ando, Toshinari; Hiyama, Tadao; Kato, Takashi; Isono, Takaaki; et al.

Teion Kogaku, 36(8), p.478 - 485, 2001/08

no abstracts in English

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