Internally Cu-stabilized RHQT NbAl superconductors with Ta matrix

タンタル母材内部安定化急熱急冷変態法NbAl超伝導体

竹内 孝夫*; 田川 浩平*; 野田 哲司*; 伴野 信哉*; 飯嶋 安男*; 菊池 章弘*; 北口 仁*; 小菅 通雄*; 土屋 清澄*; 小泉 徳潔; 西村 新*

Takeuchi, Takao*; Tagawa, Kohei*; Noda, Tetsuji*; Banno, Nobuya*; Iijima, Yasuo*; Kikuchi, Akihiro*; Kitaguchi, Hitoshi*; Kosuge, Michio*; Tsuchiya, Kiyosumi*; Koizumi, Norikiyo; Nishimura, Arata*

次期核融合炉では、16T以上の高磁場で大電流を流す導体が必要となる。急熱急冷変態法(RHQT)NbAl線は、2次熱処理前に撚線加工が行えるので、RHQT-NbAl CIC導体は、その有力な候補導体として考えられている。CIC導体で使用する丸線には、従来は、1900C程度の1次熱処理でNb母材と反応しない銀を安定化材として使用していた。しかし、銀,Nbには放射化の問題があるため、タンタルを母材とし、安定化材として銅を使用する製造方法の開発を試みた。

Next generation nuclear fusion magnets would require a high-current conductor in fields more than 16 T. A CIC conductor of the rapid RHQT processed NbAl may be a promising candidate. Good deformability of intermediately-formed bcc supersaturated-solid solution indeed allowed fabricating such a CIC conductor, which would be subsequently transformation annealed. Ag has been internally included as a basic constituent of a round strand so far, because Ag is almost non-reactive with Nb matrix during the RHQ. However, both of Ag and Nb are not suitable nuclei from the viewpoint of radioactivity when irradiated with neutrons. Recently, we have succeeded in replacing the Nb matrix with Ta that has the advantage of shorter half-life of radioactivity. In the present study, an attempt has been made to replace the Ag internal stabilizer with Cu, in the aim of further reducing radioactivity, based on anticipation that Ta would be less reactive with Cu than Nb did.