ITER用NbSn超伝導素線のJcBT特性の測定

Measurement of the JcBT characteristics of NbSn superconductor for ITER

神門 剛*; 辺見 努; 布谷 嘉彦; 礒野 高明; 松井 邦浩; 小泉 徳潔; 奥野 清

Kamikado, Takeshi*; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Koizumi, Norikiyo; Okuno, Kiyoshi

ITER超伝導コイル用に原子力機構が開発したNbSn超伝導素線の広範な磁場,温度,歪み中での臨界特性評価を目的に、物質材料研究機構の強磁場センターが所有する評価試験設備の改良,調整及び臨界電流の測定を共同研究により行った。本装置は酸化物超伝導素線の計測を目的に開発されたため、より温度領域が低いNbSn超伝導素線に使用した場合、目的の温度領域において温度が不安定となり正しい測定ができない問題があった。そこで、新たにサンプル部にヒータと極低温温度計を追加し、ヒータ出力を温度でフィードバック制御し、さらに、サンプルを冷却する冷媒の流量を温度により調整する、新しい試験手法の確立を行った。そして、本試験手法を用い、ITER用NbSn素線の臨界電流を磁場領域11-14T,温度領域4.2-10K、及び歪み領域-1-1%で測定を行った。その結果、低い温度領域で安定した測定を行うことができ、臨界特性の評価が可能となった。開発したNbSn超伝導素線は、ITERの運転条件での臨界電流密度が要求値に比較し19%大きく、十分な裕度が確保できることが確認できた。

For evaluation of critical characteristics of NbSn superconductor that JAEA had developed for the ITER superconducting coil, in wide magnetic field, temperature and strain, the improvement and adjustment of the test equipment that Tsukuba Magnet lab of the NIMS owned, and the measurement of the critical current were done by a joint research. The temperature became unstable in a target temperature when using it for NbSn superconductor that the temperature is low because this device was developed to measure oxide superconductor and there was a problem that a correct measurement was not able to be done. Then, the heater controlled by temperature and the temperature sensor were newly added to the sample, it adjusted in addition according to flowing quantity and the temperature of helium that cooled the sample, and a new technique was established. And, the critical current of NbSn wire for ITER was measured by using the examination technique by magnetic field area 11-14T, temperature field 4.2-10K, and strain area -1-1%. As a result, a measurement steady in a low temperature field was able to be done, and the evaluation of a critical characteristic became possible. It was able to be confirmed to developed NbSn superconductor that there was a performance that the critical current density in the operating condition of ITER was 19% larger than the demand value, and is more enough.