The Experts below are selected from a list of 1929 Experts worldwide ranked by ideXlab platform

Norikiyo Koizumi - One of the best experts on this subject based on the ideXlab platform.

  • First qualification of ITER Toroidal Field Coil conductor jacketing
    Fusion Engineering and Design, 2011
    Co-Authors: K. Hamada, Norikiyo Koizumi, Kunihiro Matsui, Yoshihiko Nunoya, Takaaki Isono, Y. Takahashi, K. Kawano, M. Oshikiri, F. Tsutsumi, H Nakajima
    Abstract:

    Abstract The Japan Atomic Energy Agency (JAEA) has the responsibility to procure 25% of the ITER Toroidal Field Coil conductors as the Japanese Domestic Agency (JADA) in the ITER project. The TF conductor is a circular shaped, cable-in-Conduit conductor, composed of a cable and a stainless Steel Conduit (jacket). The outer diameter and maximum length of the TF conductor are 43.7 mm and 760 m, respectively. JAEA started to produce strand, cables and jacket sections and to construct a conductor manufacturing (jacketing) facility in 2008. Following preparation in December 2009 of the jacketing facility, the dummy cable, the jacket sections and fabrication procedures, such as welding, cable insertion, compaction and spooling, JAEA manufactured a 760 m long Cu dummy conductor for process qualification. Into the 760 m long Cu dummy conductor jacketing, JAEA successfully inserted the cable with a maximum force of 32 kN. The outer diameter of the cross section of the spooled conductor was 43.7 ± 0.15 mm, which complies with the ITER target requirement of 43.7 ± 0.3 mm. Following qualification of all manufacturing processes, JAEA has started to fabricate superconducting conductors for the TF coils.

  • Evaluation of bending strain dependence of critical current of Nb3Al conductor for coils with react-and-wind method
    2007
    Co-Authors: Kaname Kizu, T. Ando, Makoto Matsukawa, Norikiyo Koizumi, Katsuhiro Shimada, Yoshimitsu Hishinuma, Y. Miura, Arata Nishimura, Katsuhiko Tsuchiya, Kiyoshi Okuno
    Abstract:

    Abstract In order to clarify the limitation of bending strain in conductor to fabricate the toroidal field coils of DEMO reactor by react-and-wind (R&W) method, the effect of bending strain on the critical currents (Ic) of Nb3Al cable-in-Conduit (CIC) conductor was investigated using the newly developed apparatus which can bend cooled sample from outside of cryostat. The Nb3Al strand manufactured by jelly roll process was 0.74 mm in diameter with the copper/non-copper ratio of 4.0. The CIC conductor sample which consisted of 54 Nb3Al strands and 27 copper wires inserted into a stainless Steel Conduit was 12.4 mm in diameter and 2.3 m in length. The CIC conductor was wound into a torsion coil spring shape with 4.5 turns and 150 mm in diameter. The bending strain and external magnetic field ranges for Ic measurement were from 0% to 0.6% and from 9.2 T to 11.3 T, respectively. It was clearly shown that the Ic decrease of the CIC conductor by bending is considerably low compared with that of strand, indicating the relaxation of intrinsic strain in Nb3Al filaments in CIC conductor due to the cabling effect. The Ic was not decreased up to 0.4% in bending strain and slightly decreased to 96% of initial Ic at 0.55% in bending strain. This indicates that the R&W method with bending strain of 0.6% is fully applied to the coil fabrication method. The furnace size for heat-treatment for R&W method becomes half of wind-and-react (W&R) method.

  • Effects of Tensile and Compressive Strain on Critical Currents of $rm Nb_3rm Al$ Strand and Cable-in-Conduit Conductor
    IEEE Transactions on Applied Superconductivity, 2006
    Co-Authors: Kaname Kizu, T. Ando, K Tsuchiya, Makoto Matsukawa, Norikiyo Koizumi, Katsuhiro Shimada, Yoshimitsu Hishinuma, Y. Miura, Arata Nishimura, Kiyoshi Okuno
    Abstract:

    Effects of tensile and compressive strain on critical currents (I c) of Nb3Al strand and cable-in-Conduit (CIC) conductor were investigated using a newly developed apparatus. The Nb 3Al strand manufactured by jelly roll process was 0.74 mm in diameter with a copper/noncopper ratio of 4.05. The CIC conductor sample which consists of two Nb3Al strands and one copper wire inserted into a stainless Steel Conduit was prepared. The effective strain and magnetic field ranges for the CIC conductor sample were from -0.91% to +0.26% and from 6 T to 11 T, respectively. It is clearly shown that the Ic decrease of the CIC conductor sample by longitudinal strain is relieved considerably compared with the strand sample, indicating the relaxation of intrinsic strain in Nb3Al filaments in CIC conductor due to the cabling effect. The relaxation effect is about +0.1% for -0.8% in effective strain of CIC conductor

  • Application of react-and-wind method to D-shaped test coil using the 20 kA Nb/sub 3/Al conductor developed for JT-60SC
    IEEE Transactions on Appiled Superconductivity, 2004
    Co-Authors: Kaname Kizu, T. Ando, K Tsuchiya, Norikiyo Koizumi, Kunihiro Matsui, Y. Miura, Kazuya Hamada, Eiji Hara, K. Imahashi, S. Ishida
    Abstract:

    Using a 20 kA Nb/sub 3/Al cable-in-Conduit (CIC) conductor, a two-turn D-shaped test coil with a height of 2.0 m and a width of 1.8 m was fabricated by a react-and-wind (R&W) method. After heat treatment, the conductor was formed to the D-shaped coil. Bending strain of the conductor is /spl plusmn/0.4% at critical current I/sub c/ test section. The I/sub c/ exceeded 31.4 kA at 7.3 T, 4.2 K. In spite of the stainless Steel Conduit, a critical current density J/sub c/ of 89% of the strand value was attained. The total strain of the D-shaped test coil was about -0.57%, the same as the triplex-CIC sample fabricated by a W&R method, indicating that bending did not influence the I/sub c/. The I/sub c/ at 7.4 T, 5.6 K including the margin of 1 K exceeds the operational current. Therefore, it was concluded that the R&W method is quite appropriate for the toroidal field coil of JT-60SC.

  • Evaluation of strain applied to strands in a 13 T-46 kA Nb3Al cable-in-Conduit conductor
    Superconductor Science and Technology, 2003
    Co-Authors: Norikiyo Koizumi, Hideo Nakajima, Kunihiro Matsui, Yoshihiko Nunoya, Toshinari Ando, Kiyoshi Okuno
    Abstract:

    A 13 T–46 kA Nb3Al coil, a Nb3Al insert, has been developed to demonstrate the applicability of the react-and-wind technique to toroidal field (TF) coils of a fusion reactor, such as ITER. It is estimated that a conductor is subjected to ≈0.4% bending strain after heat treatment when the react-and-wind method is applied to the TF coil fabrication. Therefore, 0.4% bending strain was artificially applied to the Nb3Al insert conductor after the heat treatment. Since a stainless Steel Conduit was used in this conductor, the strands are subjected to the compressive strains due to thermal stress. The effective strains applied to the strands are estimated by comparing the critical current test results of the Nb3Al insert at 10–13 T and calculation. Those due to thermal stress and conductor bending were evaluated to be ≈−0.4% and ≈0%, respectively. The effective strain by the conductor bending is sufficiently small so as not to affect the critical current performance of the Nb3Al conductor. In addition, the evaluated strain of the Nb3Al conductor is compared with those of same scale Nb3Sn conductors, in which there is an unexpected strain, which is proportional to the electromagnetic force. Such strain was not observed in the Nb3Al conductor. One of the explanations is higher rigidity of the Nb3Al strand than the Nb3Sn one. This shows that a Nb3Al conductor is suitable for application to large magnets, such as the TF coil of the fusion machine, which experiences large electromagnetic force in the conductor.

Kunihiro Matsui - One of the best experts on this subject based on the ideXlab platform.

  • First qualification of ITER Toroidal Field Coil conductor jacketing
    Fusion Engineering and Design, 2011
    Co-Authors: K. Hamada, Norikiyo Koizumi, Kunihiro Matsui, Yoshihiko Nunoya, Takaaki Isono, Y. Takahashi, K. Kawano, M. Oshikiri, F. Tsutsumi, H Nakajima
    Abstract:

    Abstract The Japan Atomic Energy Agency (JAEA) has the responsibility to procure 25% of the ITER Toroidal Field Coil conductors as the Japanese Domestic Agency (JADA) in the ITER project. The TF conductor is a circular shaped, cable-in-Conduit conductor, composed of a cable and a stainless Steel Conduit (jacket). The outer diameter and maximum length of the TF conductor are 43.7 mm and 760 m, respectively. JAEA started to produce strand, cables and jacket sections and to construct a conductor manufacturing (jacketing) facility in 2008. Following preparation in December 2009 of the jacketing facility, the dummy cable, the jacket sections and fabrication procedures, such as welding, cable insertion, compaction and spooling, JAEA manufactured a 760 m long Cu dummy conductor for process qualification. Into the 760 m long Cu dummy conductor jacketing, JAEA successfully inserted the cable with a maximum force of 32 kN. The outer diameter of the cross section of the spooled conductor was 43.7 ± 0.15 mm, which complies with the ITER target requirement of 43.7 ± 0.3 mm. Following qualification of all manufacturing processes, JAEA has started to fabricate superconducting conductors for the TF coils.

  • Application of react-and-wind method to D-shaped test coil using the 20 kA Nb/sub 3/Al conductor developed for JT-60SC
    IEEE Transactions on Appiled Superconductivity, 2004
    Co-Authors: Kaname Kizu, T. Ando, K Tsuchiya, Norikiyo Koizumi, Kunihiro Matsui, Y. Miura, Kazuya Hamada, Eiji Hara, K. Imahashi, S. Ishida
    Abstract:

    Using a 20 kA Nb/sub 3/Al cable-in-Conduit (CIC) conductor, a two-turn D-shaped test coil with a height of 2.0 m and a width of 1.8 m was fabricated by a react-and-wind (R&W) method. After heat treatment, the conductor was formed to the D-shaped coil. Bending strain of the conductor is /spl plusmn/0.4% at critical current I/sub c/ test section. The I/sub c/ exceeded 31.4 kA at 7.3 T, 4.2 K. In spite of the stainless Steel Conduit, a critical current density J/sub c/ of 89% of the strand value was attained. The total strain of the D-shaped test coil was about -0.57%, the same as the triplex-CIC sample fabricated by a W&R method, indicating that bending did not influence the I/sub c/. The I/sub c/ at 7.4 T, 5.6 K including the margin of 1 K exceeds the operational current. Therefore, it was concluded that the R&W method is quite appropriate for the toroidal field coil of JT-60SC.

  • Evaluation of strain applied to strands in a 13 T-46 kA Nb3Al cable-in-Conduit conductor
    Superconductor Science and Technology, 2003
    Co-Authors: Norikiyo Koizumi, Hideo Nakajima, Kunihiro Matsui, Yoshihiko Nunoya, Toshinari Ando, Kiyoshi Okuno
    Abstract:

    A 13 T–46 kA Nb3Al coil, a Nb3Al insert, has been developed to demonstrate the applicability of the react-and-wind technique to toroidal field (TF) coils of a fusion reactor, such as ITER. It is estimated that a conductor is subjected to ≈0.4% bending strain after heat treatment when the react-and-wind method is applied to the TF coil fabrication. Therefore, 0.4% bending strain was artificially applied to the Nb3Al insert conductor after the heat treatment. Since a stainless Steel Conduit was used in this conductor, the strands are subjected to the compressive strains due to thermal stress. The effective strains applied to the strands are estimated by comparing the critical current test results of the Nb3Al insert at 10–13 T and calculation. Those due to thermal stress and conductor bending were evaluated to be ≈−0.4% and ≈0%, respectively. The effective strain by the conductor bending is sufficiently small so as not to affect the critical current performance of the Nb3Al conductor. In addition, the evaluated strain of the Nb3Al conductor is compared with those of same scale Nb3Sn conductors, in which there is an unexpected strain, which is proportional to the electromagnetic force. Such strain was not observed in the Nb3Al conductor. One of the explanations is higher rigidity of the Nb3Al strand than the Nb3Sn one. This shows that a Nb3Al conductor is suitable for application to large magnets, such as the TF coil of the fusion machine, which experiences large electromagnetic force in the conductor.

  • Development of high Cu ratio Nb/sub 3/Al and Nb/sub 3/Sn CICCs for superconducting toroidal field coils of JT-60
    IEEE Transactions on Appiled Superconductivity, 2002
    Co-Authors: Kaname Kizu, K Tsuchiya, S. Ishida, Akira Sakasai, Makoto Matsukawa, Kunihiro Matsui, Takaaki Isono, Y. Miura, T. Ando
    Abstract:

    Two types of cable-in-Conduit conductors (CICCs) for the JT-60 toroidal field coil (TFC) have been developed. The operational conditions of this conductor are 7.4 T in a maximum magnetic field and 19.4 kA in operational current. Each conductor consists of a stainless Steel Conduit (17 mm in inner diameter) containing 216 high performance superconducting strand (Nb/sub 3/Al or Nb/sub 3/Sn) and 108 copper wires. The diameter of strand is 0.74 mm including 2-/spl mu/m Cr plating. In order to attain a compact and stable coil, strands with high Cu/non-Cu ratio and high critical current density (Jc) were developed. The Cu/non-Cu ratio of Nb/sub 3/Al and Nb/sub 3/Sn strands are 4.1 and 3.6, respectively. The noncopper J/sub c/ of developed Nb/sub 3/Al and Nb/sub 3/Sn strands were 1914 A/mm/sup 2/ and 1843 A/mm/sup 2/ at 7.4 T, 4.2 K, respectively. Measurements of critical current (I/sub c/) of full size conductors showed that the I/sub c/ of Nb/sub 3/Al and Nb/sub 3/Sn CICCs were 98% and 79% of I/sub c/ estimated from I/sub c/ in strands. These values exceed the target values indicating that the developed conductors are quite appropriate for TFC of JT-60.

  • Evaluation of Critical Current Performance of an Nb3Al Conductor with Stainless Steel Conduit
    TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan), 2001
    Co-Authors: Norikiyo Koizumi, Yoshikazu Takahashi, Hideo Nakajima, Yoshinori Tsuchiya, Kunihiro Matsui, Yoshihiko Nunoya, Toshinari Ando, Tadao Hiyama, Takashi Kato, Takaaki Isono
    Abstract:

    An Nb3Al conductor with stainless Steel (SS) Conduit has been developed in the framework of ITER Engineering Design Activity. The critical current performance of this conductor was experimentally investigated by using a short conductor sample. The results show that the critical current achieves the expected, resulting in demonstrating the validity of the fabrication method. The thermal strain is generally applied to the strands if SS Conduit is used because of the different thermal expansion between the strands and SS Conduit. However, it was not applied in our sample, since the conductor length, a few meters, is too short to keep it by friction force between the cable and Conduit. The thermal strain applied to the strands in a long conductor is therefore estimated by using the solid model, in which the strain on the strands and Conduit are calculated from the equilibrium of their thermal forces, ignoring the effect of cabling on relaxation of the strain on the strands. The results indicate that the Nb3Al strands are subjected to a compressive thermal strain of less than 0.4%. The critical current degradation by this is less than 10%, even though the SS Conduit is used. Consequently, its critical current is estimated to be 90kA, which is sufficiently high compared with the nominal, 46kA, at 13T and 4.5K. Furthermore, it should be noted that the large thermal force, 80kN, appears after the heat treatment at room temperature.

Patricia B. Horton - One of the best experts on this subject based on the ideXlab platform.

  • Performance Evaluation of Steel-Conduit-Enclosed
    1999
    Co-Authors: A. P. Sakis Meliopoulos, Elias N. Glytsis, Richard E. Loyd, Patricia B. Horton
    Abstract:

    The performance of Steel electric metallic tubing, intermediate metal Conduit, and rigid-Conduit-enclosed power distribution systems with respect to safety is examined. A model of the integrated system has been developed and validated with full-scale high-current tests. The tests and model indicate the suitability of Steel Conduit as a ground conductor.

  • Closure to discussion of "Performance evaluation of Steel-Conduit-enclosed power systems"
    IEEE Transactions on Industry Applications, 1999
    Co-Authors: A. P. Sakis Meliopoulos, Richard E. Loyd, E.n. Glysis, Patricia B. Horton
    Abstract:

    The authors of "Performance evaluation of Steel-Conduit-enclosed power systems" (see ibid., vol. 35, no. 3, p. 515-23, 1999) respond to the comments on the original paper. They argue that the intention of their paper is that the users should use the proper value of overcurrent device rating as it will be dictated by the application.

  • Performance evaluation of Steel Conduit enclosed power systems
    IAS '96. Conference Record of the 1996 IEEE Industry Applications Conference Thirty-First IAS Annual Meeting, 1
    Co-Authors: A.p. Sakis Meliopoulous, Elias N. Glytsis, Richard E. Loyd, Patricia B. Horton
    Abstract:

    The performance of Steel electric metallic tubing, intermediate metal Conduit and rigid-Conduit-enclosed power distribution systems with respect to safety is examined. A model of the integrated system has been developed and validated with full-scale high-current tests. The tests and model indicate the suitability of Steel Conduit as a ground conductor.

Toshinari Ando - One of the best experts on this subject based on the ideXlab platform.

  • Development of a 30 m long Nb3Al superconducting conductor jacketed with a round-in-square type stainless Steel Conduit for the toroidal field coils in JT-60SC
    Fusion Engineering and Design, 2004
    Co-Authors: K Tsuchiya, Kaname Kizu, Akira Sakasai, Makoto Matsukawa, Hideo Nakajima, Toshinari Ando, Y. Miura, Shinichi Ishida
    Abstract:

    Abstract The modification of JT-60 was programmed to be a superconducting tokamak (JT-60SC) that has superconducting toroidal field (TF) and poloidal field coils. The Nb 3 Al superconductor was developed in order to apply to the TF coil system in JT-60SC. The TF coil conductor was designed with a cable-in-Conduit (CIC) type. This conductor was Nb 3 Al cable jacketed into stainless Steel (SS) Conduit. As the first step of SS Conduit production, the 10 m long round-in-square type tubes were successfully fabricated within eccentricity tolerance of the tube hole ( 3 Al CIC conductor was successfully fabricated, so that a feasibility of mass-producing CIC conductor applied to the real machine was obtained.

  • Evaluation of strain applied to strands in a 13 T-46 kA Nb3Al cable-in-Conduit conductor
    Superconductor Science and Technology, 2003
    Co-Authors: Norikiyo Koizumi, Hideo Nakajima, Kunihiro Matsui, Yoshihiko Nunoya, Toshinari Ando, Kiyoshi Okuno
    Abstract:

    A 13 T–46 kA Nb3Al coil, a Nb3Al insert, has been developed to demonstrate the applicability of the react-and-wind technique to toroidal field (TF) coils of a fusion reactor, such as ITER. It is estimated that a conductor is subjected to ≈0.4% bending strain after heat treatment when the react-and-wind method is applied to the TF coil fabrication. Therefore, 0.4% bending strain was artificially applied to the Nb3Al insert conductor after the heat treatment. Since a stainless Steel Conduit was used in this conductor, the strands are subjected to the compressive strains due to thermal stress. The effective strains applied to the strands are estimated by comparing the critical current test results of the Nb3Al insert at 10–13 T and calculation. Those due to thermal stress and conductor bending were evaluated to be ≈−0.4% and ≈0%, respectively. The effective strain by the conductor bending is sufficiently small so as not to affect the critical current performance of the Nb3Al conductor. In addition, the evaluated strain of the Nb3Al conductor is compared with those of same scale Nb3Sn conductors, in which there is an unexpected strain, which is proportional to the electromagnetic force. Such strain was not observed in the Nb3Al conductor. One of the explanations is higher rigidity of the Nb3Al strand than the Nb3Sn one. This shows that a Nb3Al conductor is suitable for application to large magnets, such as the TF coil of the fusion machine, which experiences large electromagnetic force in the conductor.

  • Evaluation of Critical Current Performance of an Nb3Al Conductor with Stainless Steel Conduit
    TEION KOGAKU (Journal of Cryogenics and Superconductivity Society of Japan), 2001
    Co-Authors: Norikiyo Koizumi, Yoshikazu Takahashi, Hideo Nakajima, Yoshinori Tsuchiya, Kunihiro Matsui, Yoshihiko Nunoya, Toshinari Ando, Tadao Hiyama, Takashi Kato, Takaaki Isono
    Abstract:

    An Nb3Al conductor with stainless Steel (SS) Conduit has been developed in the framework of ITER Engineering Design Activity. The critical current performance of this conductor was experimentally investigated by using a short conductor sample. The results show that the critical current achieves the expected, resulting in demonstrating the validity of the fabrication method. The thermal strain is generally applied to the strands if SS Conduit is used because of the different thermal expansion between the strands and SS Conduit. However, it was not applied in our sample, since the conductor length, a few meters, is too short to keep it by friction force between the cable and Conduit. The thermal strain applied to the strands in a long conductor is therefore estimated by using the solid model, in which the strain on the strands and Conduit are calculated from the equilibrium of their thermal forces, ignoring the effect of cabling on relaxation of the strain on the strands. The results indicate that the Nb3Al strands are subjected to a compressive thermal strain of less than 0.4%. The critical current degradation by this is less than 10%, even though the SS Conduit is used. Consequently, its critical current is estimated to be 90kA, which is sufficiently high compared with the nominal, 46kA, at 13T and 4.5K. Furthermore, it should be noted that the large thermal force, 80kN, appears after the heat treatment at room temperature.

  • Measurement of quench back behavior on the normal zone propagation velocity in a CICC
    Cryogenics, 1994
    Co-Authors: Toshinari Ando, Takashi Kato, Masataka Nishi, Jun Yoshida, Noboru Itoh, Susumu Shimamoto
    Abstract:

    Abstract The normal zone propagation velocity in a cable-in-Conduit conductor (CICC) has beenexperimentally investigated. The CICC used for this experiment consists of eighteen NbTi/Cu composite strands inserted in a stainless Steel Conduit with 26 m length. The measurement of the propagation velocity of the normal front was carried out by observing the appearance of the resistive voltage on each of taps attached to the conductor. In this experiment the quench back behavior that the propagation velocity is suddenly increased, was observed, which has been predicted from numerical simulations by C. Luongo et al. The behavior was influenced by the initial helium pressure within the Conduit and was easy to occur at low pressure.

Kiyoshi Okuno - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of bending strain dependence of critical current of Nb3Al conductor for coils with react-and-wind method
    2007
    Co-Authors: Kaname Kizu, T. Ando, Makoto Matsukawa, Norikiyo Koizumi, Katsuhiro Shimada, Yoshimitsu Hishinuma, Y. Miura, Arata Nishimura, Katsuhiko Tsuchiya, Kiyoshi Okuno
    Abstract:

    Abstract In order to clarify the limitation of bending strain in conductor to fabricate the toroidal field coils of DEMO reactor by react-and-wind (R&W) method, the effect of bending strain on the critical currents (Ic) of Nb3Al cable-in-Conduit (CIC) conductor was investigated using the newly developed apparatus which can bend cooled sample from outside of cryostat. The Nb3Al strand manufactured by jelly roll process was 0.74 mm in diameter with the copper/non-copper ratio of 4.0. The CIC conductor sample which consisted of 54 Nb3Al strands and 27 copper wires inserted into a stainless Steel Conduit was 12.4 mm in diameter and 2.3 m in length. The CIC conductor was wound into a torsion coil spring shape with 4.5 turns and 150 mm in diameter. The bending strain and external magnetic field ranges for Ic measurement were from 0% to 0.6% and from 9.2 T to 11.3 T, respectively. It was clearly shown that the Ic decrease of the CIC conductor by bending is considerably low compared with that of strand, indicating the relaxation of intrinsic strain in Nb3Al filaments in CIC conductor due to the cabling effect. The Ic was not decreased up to 0.4% in bending strain and slightly decreased to 96% of initial Ic at 0.55% in bending strain. This indicates that the R&W method with bending strain of 0.6% is fully applied to the coil fabrication method. The furnace size for heat-treatment for R&W method becomes half of wind-and-react (W&R) method.

  • Effects of Tensile and Compressive Strain on Critical Currents of $rm Nb_3rm Al$ Strand and Cable-in-Conduit Conductor
    IEEE Transactions on Applied Superconductivity, 2006
    Co-Authors: Kaname Kizu, T. Ando, K Tsuchiya, Makoto Matsukawa, Norikiyo Koizumi, Katsuhiro Shimada, Yoshimitsu Hishinuma, Y. Miura, Arata Nishimura, Kiyoshi Okuno
    Abstract:

    Effects of tensile and compressive strain on critical currents (I c) of Nb3Al strand and cable-in-Conduit (CIC) conductor were investigated using a newly developed apparatus. The Nb 3Al strand manufactured by jelly roll process was 0.74 mm in diameter with a copper/noncopper ratio of 4.05. The CIC conductor sample which consists of two Nb3Al strands and one copper wire inserted into a stainless Steel Conduit was prepared. The effective strain and magnetic field ranges for the CIC conductor sample were from -0.91% to +0.26% and from 6 T to 11 T, respectively. It is clearly shown that the Ic decrease of the CIC conductor sample by longitudinal strain is relieved considerably compared with the strand sample, indicating the relaxation of intrinsic strain in Nb3Al filaments in CIC conductor due to the cabling effect. The relaxation effect is about +0.1% for -0.8% in effective strain of CIC conductor

  • Evaluation of strain applied to strands in a 13 T-46 kA Nb3Al cable-in-Conduit conductor
    Superconductor Science and Technology, 2003
    Co-Authors: Norikiyo Koizumi, Hideo Nakajima, Kunihiro Matsui, Yoshihiko Nunoya, Toshinari Ando, Kiyoshi Okuno
    Abstract:

    A 13 T–46 kA Nb3Al coil, a Nb3Al insert, has been developed to demonstrate the applicability of the react-and-wind technique to toroidal field (TF) coils of a fusion reactor, such as ITER. It is estimated that a conductor is subjected to ≈0.4% bending strain after heat treatment when the react-and-wind method is applied to the TF coil fabrication. Therefore, 0.4% bending strain was artificially applied to the Nb3Al insert conductor after the heat treatment. Since a stainless Steel Conduit was used in this conductor, the strands are subjected to the compressive strains due to thermal stress. The effective strains applied to the strands are estimated by comparing the critical current test results of the Nb3Al insert at 10–13 T and calculation. Those due to thermal stress and conductor bending were evaluated to be ≈−0.4% and ≈0%, respectively. The effective strain by the conductor bending is sufficiently small so as not to affect the critical current performance of the Nb3Al conductor. In addition, the evaluated strain of the Nb3Al conductor is compared with those of same scale Nb3Sn conductors, in which there is an unexpected strain, which is proportional to the electromagnetic force. Such strain was not observed in the Nb3Al conductor. One of the explanations is higher rigidity of the Nb3Al strand than the Nb3Sn one. This shows that a Nb3Al conductor is suitable for application to large magnets, such as the TF coil of the fusion machine, which experiences large electromagnetic force in the conductor.

  • Experimental results of stability and current sharing of NbTi cable-in-Conduit conductors for the poloidal field coils
    IEEE Transactions on Applied Superconductivity, 1993
    Co-Authors: Y. Takahashi, Norikiyo Koizumi, Takashi Kato, Takaaki Isono, Masataka Nishi, Kiyoshi Okuno, Y. Wadayama, Kiyoshi Yoshida, Makoto Sugimoto, T. Sasaki
    Abstract:

    Japan Atomic Energy Research Institute has developed and tested the 30-kA NbTi Demo Poloidal Coils whose stored energy and inner diameter were 30 MJ and 1 m, respectively. The conductor of these coils consists of Formvar-coated NbTi strands inside the stainless Steel Conduit. During the charging test, an instability was observed. Stability and current sharing of the cable-in-Conduit conductor were studied to solve the problem. These experimental results clarified that the cause of the instability was the low stability margin of the conductor due to the nonuniformity of current distribution between the strands. Therefore, the surface of the strand of the new conductor was designed to be chromium instead of the Formvar. Two types of the new 30-kA conductors were fabricated. One of these conductors was tested, and good results were obtained. These new conductors can be used for the conductor of the outer ring coils of the International Thermonuclear Experimental Reactor (ITER) with minor modifications. >