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Hamada, Kazuya; Nakajima, Hideo; Kawano, Katsumi; Takano, Katsutoshi*; Tsutsumi, Fumiaki*; Seki, Shuichi*; Okuno, Kiyoshi; Fujitsuna, Nobuyuki*; Mizoguchi, Mitsuru*
IEEE Transactions on Applied Superconductivity, 16(2), p.787 - 790, 2006/06
Times Cited Count：6 Percentile：37.27(Engineering, Electrical & Electronic)no abstracts in English
Sn strand subjected to bending strainHirohashi, Masayuki*; Murakami, Haruyuki*; Ishiyama, Atsushi*; Ueda, Hiroshi*; Koizumi, Norikiyo; Okuno, Kiyoshi
IEEE Transactions on Applied Superconductivity, 16(2), p.1721 - 1724, 2006/06
Times Cited Count：9 Percentile：46.59(Engineering, Electrical & Electronic)To demonstrate the applicability of NbSn CICCs to ITER, four NbSn model coils have been constructed and tested. The experimental results showed that the measured critical current (Ic) degraded. In addition, the larger is the applied electromagnetic force, the larger the magnitude of the degradation is. The degradation in n-value was also observed. One of the explanations of this degradation is a local strand bending. This consideration has been supported by the test results. However, general dependence of Ic on periodic bending strain has not been clarified in this test since the experiments were carried out at a certain magnetic field, temperature and strain. Therefore, a numerical simulation code was developed to study the general dependence of the Ic and n-value of the NbSn strand on periodic bending strain. A distributed constant circuit model is applied to simulate current transfer among the filaments in the strand. The simulation results show relatively good agreement with the experiment results but some modification in modeling is required for more accurate simulation.
test results of a D-shaped NbAl CICC coil fabricated with a react-and-wind process for the National Centralized TokamakAndo, Toshinari*; Kizu, Kaname; Miura, Yushi*; Tsuchiya, Katsuhiko; Matsukawa, Makoto; Tamai, Hiroshi; Ishida, Shinichi; Koizumi, Norikiyo; Okuno, Kiyoshi
Fusion Engineering and Design, 75-79, p.99 - 103, 2005/11
Times Cited Count：1 Percentile：10.41(Nuclear Science & Technology)no abstracts in English
Al cable-in-conduit conductorKoizumi, Norikiyo; Matsui, Kunihiro; Kume, Etsuo; Okuno, Kiyoshi
IEEE Transactions on Applied Superconductivity, 15(2), p.1363 - 1366, 2005/06
Times Cited Count：0 Percentile：0(Engineering, Electrical & Electronic)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.
Nunoya, Yoshihiko; Isono, Takaaki; Okuno, Kiyoshi
IEEE Transactions on Applied Superconductivity, 14(2), p.1468 - 1472, 2004/06
Times Cited Count：45 Percentile：83.39(Engineering, Electrical & Electronic)The voltage temperature characteristic curve (V-T curve) observed in the large-current NbSn CIC conductor, which was used in the ITER CS Insert, showed a gradual take-off toward normal state as compared with the V-T curve of an individual strand composing the conductor. The gradual take-off corresponds to the reduction in so-called "n-value." In addition, the take-off shifted to lower temperature than that of the strand, namely lower current sharing temperature (Tcs) or lower critical current (Ic). These behaviors cannot be explained by non-uniform magnetic field accompanying enlargement of the conductor, or by non-uniform contact resistance of the conductor terminals. Investigation is therefore required to clarify the condition of each strand in such large CIC conductor, especially in terms of the strain state under large electromagnetic force. In a CIC conductor, since strands are twisted to form a cable, each strand is mechanically supported by a nearby strand at an interval related to the twist pitch. Between two supporting points, the strand is fee to move under transverse force and a cyclic deformation will occur along the strand length. We designed the apparatus to simulate this cyclic deformation and measured the V-T characteristic of the strand. When the strand received the transverse force of about 500 N/m, n-value reduced to one-fifth (about 6) of the original value, which corresponds to that observed in the CS Insert. The level of the force agreed to the electromagnetic force when the CS Insert was energized to 46 kA at 13 T (about 40 A each strand 
13 T = 520 N/m). This suggests that the transverse force acting on each strand can explain the behavior of the V-T curve of the large-current CIC conductor.
Takahashi, Yoshikazu; Yoshida, Kiyoshi; Mitchell, N.*; Bessette, D.*; Nunoya, Yoshihiko; Matsui, Kunihiro; Koizumi, Norikiyo; Isono, Takaaki; Okuno, Kiyoshi
IEEE Transactions on Applied Superconductivity, 14(2), p.1410 - 1413, 2004/06
Times Cited Count：10 Percentile：48.16(Engineering, Electrical & Electronic)Cable-in-conduit conductors that consist of about 1,000 NbSn strands with an outer diameter of about 0.8mm, have been designed for the TF and CS coils of the ITER. The rated current of these coils is 40 -68kA. Two joint types (Butt and Lap) were developed during the CS Model Coil project. The performance of these joints was evaluated during the operating tests and the satisfied results were obtained. The joints of the TF coils are located outside of the winding in a region where the magnetic field is about 2.1T, a very low value as compared to the maximum field of 11.8T at the winding. The CS joints are located at the coil outer diameter and embedded within the winding pack due to the lack of the space. The maximum fields at the CS joint and winding are 3.5 and 13T, respectively. For the TF coils and the CS, the joints are cooled in series with the conductor at the outlet. The maximum temperature increase due to the joule heating in the joints is set at 0.15K to limit the heat load on the refrigerator. It is shown that both joint types are applicable to the ITER coils.
Sn coil (CS insert)Inaguchi, Takashi*; Hasegawa, Mitsuru*; Koizumi, Norikiyo; Isono, Takaaki; Hamada, Kazuya; Sugimoto, Makoto; Takahashi, Yoshikazu
Cryogenics, 44(2), p.121 - 130, 2004/02
Times Cited Count：6 Percentile：27.8(Thermodynamics)In order to analyze the quench characteristic of a cable-in-conduit (CIC) conductor that has a sub-cooling channel at the center of conductor cross section, an axisymmetrical two-dimensional calculation model was developed. The test and calculation results of the CS insert were compared regarding the pressure drop and the behavior of the total voltage, temperature and normal zone propagation in the quench. They show good agreement. Therefore, the effectiveness of the calculation model is verified. It was also found that there is coolant convection between the central channel and bundle region even in a steady state. This makes the pressure drop in the central channel larger than that in a cylindrical pipe which has a smooth surface. In addition, it was found that the higher temperature of the coolant flowing through the central channel heats the coolant and the cable in the bundle region. It can be said that the hot coolant flowing through the central channel accelerates normal zone propagation.
Hamada, Kazuya; Takahashi, Yoshikazu; Matsui, Kunihiro; Kato, Takashi; Okuno, Kiyoshi
Cryogenics, 44(1), p.45 - 52, 2004/01
Times Cited Count：21 Percentile：61.01(Thermodynamics)In the ITER Central Solenoid Model Coil (CSMC) and a CS Insert Coil (CSIC) experiment, a pressure drop of the CSIC decreased by about 12% at 40 kA, 10 T and coupling losses indicated an transport current dependence. As a result of pressure drop analysis, an electromagnetic force causes a compressive deformation of cable in a jacket and a new flow passage was generated as a gap between cable and jacket. The cable deformation causes a decrease of a contact electrical resistance between strands and an increase of coupling losses. Taking account of the electromagnetic force dependency of a coupling time constant, calculated coupling losses show a good agreement with measured coupling losses at a pulsed operation of CSMC and CSIC.
Al cable-in-conduit conductorKoizumi, Norikiyo; Nunoya, Yoshihiko; Matsui, Kunihiro; Nakajima, Hideo; Ando, Toshinari*; Okuno, Kiyoshi
Superconductor Science and Technology, 16(9), p.1092 - 1096, 2003/09
Times Cited Count：9 Percentile：45.93(Physics, Applied)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.
Al cable-in-conduit conductor under electromagnetic force; Relation between pressure drop characteristics and cable stiffnessHamada, Kazuya; Matsui, Kunihiro; Takahashi, Yoshikazu; Nakajima, Hideo; Kato, Takashi; CS Model Coil Test Group
Teion Kogaku, 38(8), p.417 - 424, 2003/08
As one of the R&D of ITER. a hydraulic performance of NbAl insert coil was measured and compared with other NbSn conductors. It seems that a longer twist pitch will promote a triangle helium flow space among 4th twist stage cables, jacket and center channel and contribute reduction of pressure drop. Under 500 kN/m of the electromagnetic force, the pressure drop of the NbAl insert decreased by approximately 5%. NbAl conductor indicated quit rigid characteristic under the electromagnetic force and suitable for future magnet with higher magnetic field and current.
Al conductor to be applied to a fusion reactor and its application to a large superconducting coilKoizumi, Norikiyo; Okuno, Kiyoshi; Nakajima, Hideo; Ando, Toshinari*; Tsuji, Hiroshi
Teion Kogaku, 38(8), p.391 - 398, 2003/08
no abstracts in English
Al insertKoizumi, Norikiyo; Nunoya, Yoshihiko; Takayasu, Makoto*; Sugimoto, Makoto; Nabara, Yoshihiro; Oshikiri, Masayuki*; CS Model Coil Test Group
Teion Kogaku, 38(8), p.399 - 409, 2003/08
A NbAl insert was developed to demonstrate the applicability of a NbAl conductor and wind-and-react method to a TF coil of a fusion reactor by artificially applying 0.4% bending strain to the conductor after its heat treatment. The critical current test results show that the effective strains applied to the strands is almost zero. Then, the validity of the react-and-wind method was demonstrated. In addition, while an unexpected strain, which was proportional to electromagnetic force, was observed in the same scale NbSn conductor, such strain did not exist in the NbAl conductor. This shows a NbAl conductor is suitable to the application to large magnets, such as the TF coil. Furthermore, the effect of the current transfer among the strands on the critical current evaluation is studied by developing a numerical analysis code, KORO. The results figure out that the critical current of a large cable-in-conduit conductor can be easily evaluated assuming the uniform current distribution if the conductance among the strands is 10E5 S/m or less.
Al D-shaped coil fabricated by react-and-wind method for JT-60 superconducting TokamakKizu, Kaname; Miura, Yushi; Tsuchiya, Katsuhiko; Koizumi, Norikiyo; Matsui, Kunihiro; Ando, Toshinari*; Hamada, Kazuya; Hara, Eiji*; Imahashi, Koichi*; Ishida, Shinichi; et al.
Proceedings of 6th European Conference on Applied Superconductivity (EUCAS 2003), p.400 - 407, 2003/00
Toroidal field coils (TFC) of the JT-60SC consist of 18 D-shape coils. The maximum magnetic field is 7.4 T at an operational current of 19.4 kA. An advanced NbAl superconductor was developed for the TFC conductor material in JAERI. The NbAl has lower strain sensitivity on superconducting performances, and allows us to fabricate the TFC by react-and-wind (R&W) method that makes that the coil fabrication with high reliability becomes easier and the fabrication cost becomes lower. To demonstrate the coil fabrication by R&W method, a two-turn D-shape coil was developed. The D-shape coil was tested at 4.3-4.4K and 7-12T. Measured critical current (Ic) was 30 kA at 7.3 T and 4.4 K. Using the measured conductor and strand Ic values, the strain of the conductor was estimated to be -0.6%. The Ic-B-T characteristic expected by an empirical equation substituting this strain shows that the required temperature margin for TFC is satisfied. Thus, the R&W method was demonstrated to be the applicable fabrication method of the TFC.
Al cable-in-conduit conductorKoizumi, 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：64.62(Thermodynamics)In the framework of ITER-EDA, a 13T-46kA NbAl conductor with stainless steel jacket has been developed to demonstrate applicability of an NbAl conductor with react-and-wind technique to ITER-TF coils. The critical current performances of the NbAl 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.
Hamada, Kazuya; Kawano, Katsumi; Matsui, Kunihiro; Kato, Takashi; Sugimoto, Makoto; Hara, Eiji*; Okuno, Kiyoshi; Egorov, S. A.*; Rodin, I.*; Sytnikov, V. E.*; et al.
Teion Kogaku, 37(10), p.531 - 538, 2002/10
In the Engineering Design Activities of the International Thermonuclear Experimental Reactor (ITER), Toroidal Field (TF) Insert have been developed and tested successfully. In the experiment, pressure drop performance of TF insert was investigated. There were two purposes for the investigation. One is to verify the pressure drop prediction using correlations proposed by various researchers. Second is to observe a behavior of pressure drop under the electromagnetic force. The pressure drops of TF insert decreased by around 12% during current-carrying operation of 46kA at 13T. After several current-carrying operation, the friction factor of TF insert has finally reached a value which is around 12% lower than that of virgin state and was not recovered even if there were zero current. It is considered that a deformation of cable cross section inside the conductor jacket appears due to electromagnetic force and a new flow path in the jacket is generated.
Hamada, Kazuya; Koizumi, Norikiyo
Purazuma, Kaku Yugo Gakkai-Shi, 78(7), p.616 - 624, 2002/07
In the Tokamak type fusion reactor design, a forced flow superconducting coil is applied from the viewpoint to high magnetic field, high withstand voltage performance and large electromagnetic force. In the forced flow magnets, it is well known that various electromagnetic phenomena are occurred by zero resistance and diamagnetic effect of superconductor and complicated structure of cable in conduit conductor (CICC). In the R&D of CICC, the study of hysteresis losses and coupling losses CICC have a lot of progress. For example, using the optimization of filament arrangement in superconducting strand and control of contact resistance of strand, ITER model coil project have a large achievement.
Hamada, Kazuya; Takahashi, Yoshikazu; Matsui, Kunihiro; Kato, Takashi; Okuno, Kiyoshi
Teion Kogaku, 37(6), p.257 - 264, 2002/06
no abstracts in English
Hamada, Kazuya; Kato, Takashi; Kawano, Katsumi; Hara, Eiji*; Ando, Toshinari; Tsuji, Hiroshi; Okuno, Kiyoshi; Zanino, L.*; Savoldi, L.*
AIP Conference Proceedings 613, p.407 - 414, 2002/00
no abstracts in English
Koizumi, Norikiyo; Isono, Takaaki; Matsui, Kunihiro; Nunoya, Yoshihiko; Ando, Toshinari; CS Model Coil Test Group
Teion Kogaku, 36(6), p.368 - 372, 2001/06
no abstracts in English
Hamada, Kazuya; Kawano, Katsumi; Hara, Eiji*; Kato, Takashi; Shimba, Toru*; CS Model Coil Test Group
Teion Kogaku, 36(6), p.330 - 335, 2001/06
no abstracts in English
