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Journal Articles

Development of evaluation procedure for critical current of periodically bent Nb$$_{3}$$Sn strand

Kajitani, Hideki; Ishiyama, Atsushi*; Agatsuma, Ko*; Murakami, Haruyuki; Hemmi, Tsutomu; Koizumi, Norikiyo

Teion Kogaku, 50(12), p.608 - 615, 2015/12

A cable-in-conduit (CIC) conductor using Nb$$_{3}$$Sn strand is applied to an ITER TF coil. The Nb$$_{3}$$Sn strand in the conductor is periodically bent due to electromagnetic force, which causes degradation of performance. This degradation should be evaluated to predict conductor critical current performance. In a past study, a numerical simulation model was developed to evaluate the superconductivity of a periodically bent single strand. However, this model is not suitable for application to strands in the conductor because of the extensive calculation time. The author thus developed a new analytical model with a much shorter calculation time to evaluate the performance of periodically bent strand. This new model uses the classical model concept of a high transverse resistance model (HTRM). The calculated results show good agreement with the test results of a periodically bent Nb$$_{3}$$Sn strand. This indicates that a more practical solution can be achieved when evaluating the performance of periodically bent strands. Thus, the model developed in this study can be applied to evaluate the performance of conductors incorporating many strands.

Journal Articles

Numerical simulation of current distribution in cable-in-conduit conductor for ITER TF coil

Kajitani, Hideki*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Murakami, Haruyuki; Nakajima, Hideo

IEEE Transactions on Applied Superconductivity, 21(3), p.1964 - 1968, 2011/06

 Times Cited Count:3 Percentile:29.22(Engineering, Electrical & Electronic)

The critical current of cable-in-conduit conductor (CICC) for ITER TF coil was measured using SULTAN test facility. However, it was found that a non-uniform current distribution was established due to a non-uniform joint resistance. To more precisely evaluate critical current performance, solder filling joint was applied. To study the effect of solder filled joint on the current distribution, the authors developed a new analysis model. The lumped circuit model and distributed circuit model were used for the conductor and joint, respectively, and they are combined. This allow us to avoid iteration to solve distributed circuit equation, resulting in much reduction of calculation time. The simulation results show that although non-uniform current distribution can be established by ramping current, it is improved at current sharing temperature. Thus, the efficiency of solder filling joint is indicated.

Journal Articles

Development of next-generation superconducting cyclotron

Ishiyama, Atsushi*; Ueda, Hiroshi*; Fukuda, Mitsuhiro*; Hatanaka, Kichiji*; Miyahara, Nobuyuki*; Yokota, Wataru; Kashima, Naoji*; Nagaya, Shigeo*

Denki Gakkai Kenkyukai Shiryo, Chodendo Oyo Denryoku Kiki Kenkyukai (ASC-10-33), p.83 - 88, 2010/06

Therapy of tumor using radiation, especially heavy particle, is one of the effective treatment for an aged person and a malignant solid tumor. In order to spread the radiation therapy, downsizing of accelerator is necessary for reduction of its vast costs of construction and running. The quality of high temperature superconductors is improving rapidly in recent years, which may lead to realization of the downsizing. This presentation describes a conceptual design of the superconducting cyclotron and its advantage comparing to other type of accelerators.

Journal Articles

Numerical simulation of critical current performance in Nb$$_{3}$$Sn strand subjected to periodic bending deformation

Murakami, Haruyuki*; Ueda, Hiroshi*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Okuno, Kiyoshi

Denki Gakkai Rombunshi, B, 128(6), p.853 - 859, 2008/06

In the ITER Engineering Design Activity (EDA), it was revealed the critical current of the Nb$$_{3}$$Sn model coil conductor degraded by periodic strand bending caused by enormous electromagnetic force. We developed a simulation code based on the distributed circuit to investigate dependency of the critical current performance on bending strain. The results of the numerical simulations were in good agreement with the experiments. The dependence of the critical current on periodic transverse load, temperature, pitch of periodic load, thickness of Ta barrier which prevents Cu stabilizer to be contaminated by Sn, twist pitch of the strand and RRR of the bronze matrix is investigated using developed code. The results show the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that shorter twist pitch of the cable and larger bending stiffness prevent the critical current degradation.

Journal Articles

Numerical simulation of critical current degradation of Nb$$_{3}$$Sn strand in CIC conductor

Murakami, Haruyuki*; Ishiyama, Atsushi*; Ueda, Hiroshi*; Koizumi, Norikiyo; Okuno, Kiyoshi

IEEE Transactions on Applied Superconductivity, 18(2), p.1051 - 1054, 2008/06

 Times Cited Count:2 Percentile:20.21(Engineering, Electrical & Electronic)

Critical current was degraded by periodic transverse load in a CICC. A simulation code was developed to study mechanism of this degradation in details. The simulation results were compared with results of experiment in which single strand was periodically bent. Since the test results could not be simulated well in the previous work, the authors carried out improvements of the model, such as use of electro-plastic model and detail evaluation of conductance among filaments. By these improvements the agreement between the simulation and experiment can be modified. This results in verifying validity of our code. Using our code, the general dependence of the critical current degradation on strand configuration, such as barrier thickness, RRR of bronze and twist pitch of filament, are evaluated. The results show barrier thickness affects critical current performance because of its large bending rigidity. On the other hand, RRR of bronze and twist pitch of filament hardly affects critical current performance.

Journal Articles

Numerical simulation of critical current and n-value in Nb$$_{3}$$Sn strand subjected to bending strain

Murakami, Haruyuki*; Ishiyama, Atsushi*; Ueda, Hiroshi*; Koizumi, Norikiyo; Okuno, Kiyoshi

IEEE Transactions on Applied Superconductivity, 17(2), p.1394 - 1397, 2007/06

 Times Cited Count:19 Percentile:66.07(Engineering, Electrical & Electronic)

Critical current of ITER mode coil degraded as increase of electromagnetic force. It was shown that the periodic bending of the strand caused this degradation from analysis based on results of experiments in which periodic transverse load is artificially applied to single strand. However, since the experiments were carried out under a certain condition, general relation between transverse load and critical current was not obtained. The authors therefore developed a numerical simulation code. The simulation results are in good agreement with test results. The general dependence of the critical current on temperature and pitch of periodic load is studied using our code. The simulation results reveal that the reduced critical current depends on the temperature and is a function of the bending strain independent of the pitch of the periodic load.

Journal Articles

Numerical simulation of the critical current and n-value in Nb$$_{3}$$Sn strand subjected to bending strain

Hirohashi, 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:46.68(Engineering, Electrical & Electronic)

To demonstrate the applicability of Nb$$_{3}$$Sn CICCs to ITER, four Nb$$_{3}$$Sn 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 Nb$$_{3}$$Sn 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.

Oral presentation

Numerical simulation of critical characteristics in Nb$$_{3}$$Sn strand subjected to bending strain

Murakami, Haruyuki*; Ueda, Hiroshi*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Okuno, Kiyoshi

no journal, , 

no abstracts in English

Oral presentation

Numerical simulation of critical characteristics in Nb$$_{3}$$Sn strand subjected to bending strain

Murakami, Haruyuki*; Ueda, Hiroshi*; Agatsuma, Ko*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Okuno, Kiyoshi

no journal, , 

In the ITER EDA, four Nb$$_{3}$$Sn model coils were developed and tested. In these tests, it is revealed the critical current of the conductor degrades. One of the explanations of this phenomenon is the periodic strand bending caused by enormous electromagnetic forces. We developed a simulation code to investigate dependency of the critical characteristics on bending strain. The results of the numerical simulations were in good agreement with the experiments. The general dependence of the critical current on periodic transverse load, temperature, pitch of periodic load, Ta barrier thickness, twist pitch and RRR of the bornze matrix is investigated using this simulation code.

Oral presentation

Numerical simulation of critical current degradation of Nb$$_{3}$$Sn strand in CIC conductor

Murakami, Haruyuki*; Ueda, Hiroshi*; Ishiyama, Atsushi*; Koizumi, Norikiyo; Okuno, Kiyoshi

no journal, , 

no abstracts in English

Oral presentation

Numerical simulation on critical current degradation of Nb$$_{3}$$Sn strand with different cross sectional structure in CICC

Kajitani, Hideki*; Ueda, Hiroshi*; Ishiyama, Atsushi*; Murakami, Haruyuki; Koizumi, Norikiyo; Okuno, Kiyoshi

no journal, , 

no abstracts in English

Oral presentation

Numerical simulation of current distribution in CICC for ITER TF coil

Kajitani, Hideki*; Ueda, Hiroshi*; Ishiyama, Atsushi*; Murakami, Haruyuki; Koizumi, Norikiyo; Okuno, Kiyoshi

no journal, , 

no abstracts in English

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