核融合科学研究所共同研究 / 核融合炉用先進超伝導導体 / 研究調査報告書 1 Nb_3Sn系超伝導導体

Nb_3Sn conductors have been developed with great expectation as an advanced high-field superconductor to be used in fusion devices of next generation. Furtherrnore, Nb_3Sn conductors are being developed for NMR magnet and superconducting generator as well as for cryogen-free superconducting magnet. A variety of fabrication procedures, such as bronze process, internal tin process and Nb tube method, have been developed based on the diffusion reaction. Recently, Nb_3Sn conductors with ultra-thin filaments have been fabricated for AC use. Both high-field and AC performances of Nb_3Sn conductors have been significantly improved by alloying addition. The Ti-doped Nb_3Sn conductor has generated 21.5T at 1.8K operation. This report summarizes manufacturing procedures, superconducting performances and applications of Nb_3Sn conductors fabricated through different processcs in different countries. More detailed subjects included in this report are high-field properties, AC properties, conductors for fusion with large current capacities, stress-strain effect and irradiation effect as well as standardization of critical current measurement method regarding to Nb_3Sn conductors. Comprehensive grasp on the present status of Nb_3Sn conductors provided by this report will act as a useful data base for the future planning of fusion devices

Preparation of High-Field Nb_3(Al, Ge) and Nb_3Al Superconductors by Liquid Quenching and High-Energy Beam Techniques (Low-T_c Superconducting Materials Research)

Nb_3Al and its ternary compounds tapes have been prepared by continuous liquid quenching and high energy beam irradiation and Jc of the tapes has been measured in fields up to 23T. The Nb_3Al, Nb_3(Al, Ge) and Nb_3(Al, Si) alloy tapes prepared by the continuous liquid quenching have an extremely small grain size which is enough to ensure a strong flux pinning and hence high critical current density. Jc at 4.2K reaches 10^5A/cm^2 at 20T. Continuous high energy beam irradiation has been performed for Nb-Al and Nb-(Al-Ge) tapes made by powder metallurgy process. High Tc and excellent high field Jc properties have been achieved by the irradiation and subsequent annealing. Overall Jc\u27s exceeding well 10^4A/cm^2 have been obtained at 23T and 4.2K for the Nb-Al and Nb-(Al-Ge) tapes