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成果報告書詳細
管理番号20170000000386
タイトル*平成28年度中間年報 高温超電導実用化促進技術開発 高磁場マグネットシステム開発 高温超電導高安定磁場マグネットシステム技術開発(国立研究開発法人産業技術総合研究所)
公開日2017/7/6
報告書年度2016 - 2016
委託先名国立研究開発法人産業技術総合研究所
プロジェクト番号P16006
部署名省エネルギー部
和文要約
英文要約Title: Project for the Promotion to the Commercialization of High-Temperature Superconductivity Technology. Development of High Magnetic Field Magnet System. Development of HTS High Stable Magnet System Technology. (FY2016-FY2018) FY2016 Annual Report

3) Development of Superconducting Joint Technology for High-Tc Superconductors
1. Superconducting Joint Technology
a. Low magnetic field / low temperature stage for superconducting joints
To open the choices of superconducting joint processes and materials, a low magnetic field / low temperature stage for joints has been designed. We calculated magnetic field distribution around the main coil of MRI magnet system using FEM and estimated the relation between magnetic field intensity and distance. We also estimated thermal conductivity of commercial HTS conductors and calculated heat conduction along the conductors from magnets to the low temperature stage. Feasibility of heat pipe technology to cool down the stage was investigated.
b. Joint Technology using metallic paste
In order to densify the jointing part for lowering joint-resistance, uniaxial pressing or lowering ambient pressure were applied to the joint technique using the paste including nano-sized Ag or Au metal particles. Additionally, the influence of selection of the superconducting materials was also investigated. As a result, it was found that the EuBCO system has lower joint-resistance than that of GdBCO one.
The paste with Nb and other superconducting powders have been prototyped, and investigated the electrical conductivity at 4.2 K. At the same time as confirming the connections of the superconducting metal particles by TEM observation, we examined to select a system of resin, hardener, solvent etc.
c. Joint Technology by dissimilar superconductors
YBCO superconducting thin films were formed on a SrTiO3 (001) single crystal substrate by the PLD method, and Nb thin film or La1.85Sr0.15CuO4 thin films were grown by a sputtering method or a PLD method to prepare a hetero superconducting connections.
d. Connecting conductors between HTS coils
We fabricated iron-based superconducting wires of Ba1-xKxFe2As2 with different potassium concentration by using the powder-in-tube method. The wire with 0.5 diameter and 1 m length had a shaper superconducting transition at 38 K. Transport Jc of the wire was obtained 50000 [A/cm2] at 4.2 K, self-field.
2. Joint Resistance Evaluation Technology
To check the applicability of the joint resistance evaluation method, we fabricated a closed loop circuit by soldering both ends of a REBCO double pancake winding and induced current in the circuit by a copper solenoid coil in liquid nitrogen. The joint resistances derived from the current decay time constant were well agreed with those measured by four probe method. We designed a system to measure joint resistances of HTS conductors in a vector-controllable magnetic field up to 3T.
4) Protection of HTS magnets
b. Protection for persistent current mode
Detection characteristics of resistive zone of the co-winding method are compared with those of a commonly used bridge-balance method. Making a small scale double pancake coil, suppression performance of inductive voltage of the co-winding method was experimentally investigated and compared with that of the bridge-balance method. Numerical method to analyze thermal behavior of resistive zone in HTS coils has been developed and limit of quench detection voltage was calculated.
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